summaryrefslogtreecommitdiffstats
path: root/layout/generic/nsIFrame.h
blob: 3137aaee2770c4ce57f6667b1493a736211912d2 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
3069
3070
3071
3072
3073
3074
3075
3076
3077
3078
3079
3080
3081
3082
3083
3084
3085
3086
3087
3088
3089
3090
3091
3092
3093
3094
3095
3096
3097
3098
3099
3100
3101
3102
3103
3104
3105
3106
3107
3108
3109
3110
3111
3112
3113
3114
3115
3116
3117
3118
3119
3120
3121
3122
3123
3124
3125
3126
3127
3128
3129
3130
3131
3132
3133
3134
3135
3136
3137
3138
3139
3140
3141
3142
3143
3144
3145
3146
3147
3148
3149
3150
3151
3152
3153
3154
3155
3156
3157
3158
3159
3160
3161
3162
3163
3164
3165
3166
3167
3168
3169
3170
3171
3172
3173
3174
3175
3176
3177
3178
3179
3180
3181
3182
3183
3184
3185
3186
3187
3188
3189
3190
3191
3192
3193
3194
3195
3196
3197
3198
3199
3200
3201
3202
3203
3204
3205
3206
3207
3208
3209
3210
3211
3212
3213
3214
3215
3216
3217
3218
3219
3220
3221
3222
3223
3224
3225
3226
3227
3228
3229
3230
3231
3232
3233
3234
3235
3236
3237
3238
3239
3240
3241
3242
3243
3244
3245
3246
3247
3248
3249
3250
3251
3252
3253
3254
3255
3256
3257
3258
3259
3260
3261
3262
3263
3264
3265
3266
3267
3268
3269
3270
3271
3272
3273
3274
3275
3276
3277
3278
3279
3280
3281
3282
3283
3284
3285
3286
3287
3288
3289
3290
3291
3292
3293
3294
3295
3296
3297
3298
3299
3300
3301
3302
3303
3304
3305
3306
3307
3308
3309
3310
3311
3312
3313
3314
3315
3316
3317
3318
3319
3320
3321
3322
3323
3324
3325
3326
3327
3328
3329
3330
3331
3332
3333
3334
3335
3336
3337
3338
3339
3340
3341
3342
3343
3344
3345
3346
3347
3348
3349
3350
3351
3352
3353
3354
3355
3356
3357
3358
3359
3360
3361
3362
3363
3364
3365
3366
3367
3368
3369
3370
3371
3372
3373
3374
3375
3376
3377
3378
3379
3380
3381
3382
3383
3384
3385
3386
3387
3388
3389
3390
3391
3392
3393
3394
3395
3396
3397
3398
3399
3400
3401
3402
3403
3404
3405
3406
3407
3408
3409
3410
3411
3412
3413
3414
3415
3416
3417
3418
3419
3420
3421
3422
3423
3424
3425
3426
3427
3428
3429
3430
3431
3432
3433
3434
3435
3436
3437
3438
3439
3440
3441
3442
3443
3444
3445
3446
3447
3448
3449
3450
3451
3452
3453
3454
3455
3456
3457
3458
3459
3460
3461
3462
3463
3464
3465
3466
3467
3468
3469
3470
3471
3472
3473
3474
3475
3476
3477
3478
3479
3480
3481
3482
3483
3484
3485
3486
3487
3488
3489
3490
3491
3492
3493
3494
3495
3496
3497
3498
3499
3500
3501
3502
3503
3504
3505
3506
3507
3508
3509
3510
3511
3512
3513
3514
3515
3516
3517
3518
3519
3520
3521
3522
3523
3524
3525
3526
3527
3528
3529
3530
3531
3532
3533
3534
3535
3536
3537
3538
3539
3540
3541
3542
3543
3544
3545
3546
3547
3548
3549
3550
3551
3552
3553
3554
3555
3556
3557
3558
3559
3560
3561
3562
3563
3564
3565
3566
3567
3568
3569
3570
3571
3572
3573
3574
3575
3576
3577
3578
3579
3580
3581
3582
3583
3584
3585
3586
3587
3588
3589
3590
3591
3592
3593
3594
3595
3596
3597
3598
3599
3600
3601
3602
3603
3604
3605
3606
3607
3608
3609
3610
3611
3612
3613
3614
3615
3616
3617
3618
3619
3620
3621
3622
3623
3624
3625
3626
3627
3628
3629
3630
3631
3632
3633
3634
3635
3636
3637
3638
3639
3640
3641
3642
3643
3644
3645
3646
3647
3648
3649
3650
3651
3652
3653
3654
3655
3656
3657
3658
3659
3660
3661
3662
3663
3664
3665
3666
3667
3668
3669
3670
3671
3672
3673
3674
3675
3676
3677
3678
3679
3680
3681
3682
3683
3684
3685
3686
3687
3688
3689
3690
3691
3692
3693
3694
3695
3696
3697
3698
3699
3700
3701
3702
3703
3704
3705
3706
3707
3708
3709
3710
3711
3712
3713
3714
3715
3716
3717
3718
3719
3720
3721
3722
3723
3724
3725
3726
3727
3728
3729
3730
3731
3732
3733
3734
3735
3736
3737
3738
3739
3740
3741
3742
3743
3744
3745
3746
3747
3748
3749
3750
3751
3752
3753
3754
3755
3756
3757
3758
3759
3760
3761
3762
3763
3764
3765
3766
3767
3768
3769
3770
3771
3772
3773
3774
3775
3776
3777
3778
3779
3780
3781
3782
3783
3784
3785
3786
3787
3788
3789
3790
3791
3792
3793
3794
3795
3796
3797
3798
3799
3800
3801
3802
3803
3804
3805
3806
3807
3808
3809
3810
3811
3812
3813
3814
3815
3816
3817
3818
3819
3820
3821
3822
3823
3824
3825
3826
3827
3828
3829
3830
3831
3832
3833
3834
3835
3836
3837
3838
3839
3840
3841
3842
3843
3844
3845
3846
3847
3848
3849
3850
3851
3852
3853
3854
3855
3856
3857
3858
3859
3860
3861
3862
3863
3864
3865
3866
3867
3868
3869
3870
3871
3872
3873
3874
3875
3876
3877
3878
3879
3880
3881
3882
3883
3884
3885
3886
3887
3888
3889
3890
3891
3892
3893
3894
3895
3896
3897
3898
3899
3900
3901
3902
3903
3904
3905
3906
3907
3908
3909
3910
3911
3912
3913
3914
3915
3916
3917
3918
3919
3920
3921
3922
3923
3924
3925
3926
3927
3928
3929
3930
3931
3932
3933
3934
3935
3936
3937
3938
3939
3940
3941
3942
3943
3944
3945
3946
3947
3948
3949
3950
3951
3952
3953
3954
3955
3956
3957
3958
3959
3960
3961
3962
3963
3964
3965
3966
3967
3968
3969
3970
3971
3972
3973
3974
3975
3976
3977
3978
3979
3980
3981
3982
3983
3984
3985
3986
3987
3988
3989
3990
3991
3992
3993
3994
3995
3996
3997
3998
3999
4000
4001
4002
4003
4004
4005
4006
4007
4008
4009
4010
4011
4012
4013
4014
4015
4016
4017
4018
4019
4020
4021
4022
4023
4024
4025
4026
4027
4028
4029
4030
4031
4032
4033
4034
4035
4036
4037
4038
4039
4040
4041
4042
4043
4044
4045
4046
4047
4048
4049
4050
4051
4052
4053
4054
4055
4056
4057
4058
4059
4060
4061
4062
4063
4064
4065
4066
4067
4068
4069
4070
4071
4072
4073
4074
4075
4076
4077
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=2 sw=2 et tw=78: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/* interface for all rendering objects */

#ifndef nsIFrame_h___
#define nsIFrame_h___

#ifndef MOZILLA_INTERNAL_API
#error This header/class should only be used within Mozilla code. It should not be used by extensions.
#endif

#define MAX_REFLOW_DEPTH 200

/* nsIFrame is in the process of being deCOMtaminated, i.e., this file is eventually
   going to be eliminated, and all callers will use nsFrame instead.  At the moment
   we're midway through this process, so you will see inlined functions and member
   variables in this file.  -dwh */

#include <algorithm>
#include <stdio.h>

#include "CaretAssociationHint.h"
#include "FrameProperties.h"
#include "LayoutConstants.h"
#include "mozilla/layout/FrameChildList.h"
#include "mozilla/Maybe.h"
#include "mozilla/WritingModes.h"
#include "nsDirection.h"
#include "nsFrameList.h"
#include "nsFrameState.h"
#include "mozilla/ReflowOutput.h"
#include "nsITheme.h"
#include "nsLayoutUtils.h"
#include "nsQueryFrame.h"
#include "nsStringGlue.h"
#include "nsStyleContext.h"
#include "nsStyleStruct.h"
#include "Visibility.h"

#ifdef ACCESSIBILITY
#include "mozilla/a11y/AccTypes.h"
#endif

/**
 * New rules of reflow:
 * 1. you get a WillReflow() followed by a Reflow() followed by a DidReflow() in order
 *    (no separate pass over the tree)
 * 2. it's the parent frame's responsibility to size/position the child's view (not
 *    the child frame's responsibility as it is today) during reflow (and before
 *    sending the DidReflow() notification)
 * 3. positioning of child frames (and their views) is done on the way down the tree,
 *    and sizing of child frames (and their views) on the way back up
 * 4. if you move a frame (outside of the reflow process, or after reflowing it),
 *    then you must make sure that its view (or its child frame's views) are re-positioned
 *    as well. It's reasonable to not position the view until after all reflowing the
 *    entire line, for example, but the frame should still be positioned and sized (and
 *    the view sized) during the reflow (i.e., before sending the DidReflow() notification)
 * 5. the view system handles moving of widgets, i.e., it's not our problem
 */

class nsIAtom;
class nsPresContext;
class nsIPresShell;
class nsRenderingContext;
class nsView;
class nsIWidget;
class nsISelectionController;
class nsBoxLayoutState;
class nsBoxLayout;
class nsILineIterator;
class nsDisplayListBuilder;
class nsDisplayListSet;
class nsDisplayList;
class gfxSkipChars;
class gfxSkipCharsIterator;
class gfxContext;
class nsLineList_iterator;
class nsAbsoluteContainingBlock;
class nsIContent;
class nsContainerFrame;

struct nsPeekOffsetStruct;
struct nsPoint;
struct nsRect;
struct nsSize;
struct nsMargin;
struct CharacterDataChangeInfo;

namespace mozilla {

enum class CSSPseudoElementType : uint8_t;
class EventStates;
struct ReflowInput;
class ReflowOutput;

namespace layers {
class Layer;
} // namespace layers

namespace gfx {
class Matrix;
} // namespace gfx
} // namespace mozilla

/**
 * Indication of how the frame can be split. This is used when doing runaround
 * of floats, and when pulling up child frames from a next-in-flow.
 *
 * The choices are splittable, not splittable at all, and splittable in
 * a non-rectangular fashion. This last type only applies to block-level
 * elements, and indicates whether splitting can be used when doing runaround.
 * If you can split across page boundaries, but you expect each continuing
 * frame to be the same width then return frSplittable and not
 * frSplittableNonRectangular.
 *
 * @see #GetSplittableType()
 */
typedef uint32_t nsSplittableType;

#define NS_FRAME_NOT_SPLITTABLE             0   // Note: not a bit!
#define NS_FRAME_SPLITTABLE                 0x1
#define NS_FRAME_SPLITTABLE_NON_RECTANGULAR 0x3

#define NS_FRAME_IS_SPLITTABLE(type)\
  (0 != ((type) & NS_FRAME_SPLITTABLE))

#define NS_FRAME_IS_NOT_SPLITTABLE(type)\
  (0 == ((type) & NS_FRAME_SPLITTABLE))

//----------------------------------------------------------------------

#define NS_SUBTREE_DIRTY(_frame)  \
  (((_frame)->GetStateBits() &      \
    (NS_FRAME_IS_DIRTY | NS_FRAME_HAS_DIRTY_CHILDREN)) != 0)

// 1 million CSS pixels less than our max app unit measure.
// For reflowing with an "infinite" available inline space per [css-sizing].
// (reflowing with an NS_UNCONSTRAINEDSIZE available inline size isn't allowed
//  and leads to assertions)
#define INFINITE_ISIZE_COORD nscoord(NS_MAXSIZE - (1000000*60))

//----------------------------------------------------------------------

enum nsSelectionAmount {
  eSelectCharacter = 0, // a single Unicode character;
                        // do not use this (prefer Cluster) unless you
                        // are really sure it's what you want
  eSelectCluster   = 1, // a grapheme cluster: this is usually the right
                        // choice for movement or selection by "character"
                        // as perceived by the user
  eSelectWord      = 2,
  eSelectWordNoSpace = 3, // select a "word" without selecting the following
                          // space, no matter what the default platform
                          // behavior is
  eSelectLine      = 4, // previous drawn line in flow.
  // NOTE that selection code depends on the ordering of the above values,
  // allowing simple <= tests to check categories of caret movement.
  // Don't rearrange without checking the usage in nsSelection.cpp!

  eSelectBeginLine = 5,
  eSelectEndLine   = 6,
  eSelectNoAmount  = 7, // just bounce back current offset.
  eSelectParagraph = 8  // select a "paragraph"
};

enum nsSpread {
  eSpreadNone   = 0,
  eSpreadAcross = 1,
  eSpreadDown   = 2
};

// Carried out margin flags
#define NS_CARRIED_TOP_MARGIN_IS_AUTO    0x1
#define NS_CARRIED_BOTTOM_MARGIN_IS_AUTO 0x2

//----------------------------------------------------------------------

/**
 * Reflow status returned by the reflow methods. There are three
 * completion statuses, represented by two bit flags.
 *
 * NS_FRAME_COMPLETE means the frame is fully complete.
 *
 * NS_FRAME_NOT_COMPLETE bit flag means the frame does not map all its
 * content, and that the parent frame should create a continuing frame.
 * If this bit isn't set it means the frame does map all its content.
 * This bit is mutually exclusive with NS_FRAME_OVERFLOW_INCOMPLETE.
 *
 * NS_FRAME_OVERFLOW_INCOMPLETE bit flag means that the frame has
 * overflow that is not complete, but its own box is complete.
 * (This happens when content overflows a fixed-height box.)
 * The reflower should place and size the frame and continue its reflow,
 * but needs to create an overflow container as a continuation for this
 * frame. See nsContainerFrame.h for more information.
 * This bit is mutually exclusive with NS_FRAME_NOT_COMPLETE.
 * 
 * Please use the SET macro for handling
 * NS_FRAME_NOT_COMPLETE and NS_FRAME_OVERFLOW_INCOMPLETE.
 *
 * NS_FRAME_REFLOW_NEXTINFLOW bit flag means that the next-in-flow is
 * dirty, and also needs to be reflowed. This status only makes sense
 * for a frame that is not complete, i.e. you wouldn't set both
 * NS_FRAME_COMPLETE and NS_FRAME_REFLOW_NEXTINFLOW.
 *
 * The low 8 bits of the nsReflowStatus are reserved for future extensions;
 * the remaining 24 bits are zero (and available for extensions; however
 * API's that accept/return nsReflowStatus must not receive/return any
 * extension bits).
 *
 * @see #Reflow()
 */
typedef uint32_t nsReflowStatus;

#define NS_FRAME_COMPLETE             0       // Note: not a bit!
#define NS_FRAME_NOT_COMPLETE         0x1
#define NS_FRAME_REFLOW_NEXTINFLOW    0x2
#define NS_FRAME_OVERFLOW_INCOMPLETE  0x4

#define NS_FRAME_IS_COMPLETE(status) \
  (0 == ((status) & NS_FRAME_NOT_COMPLETE))

#define NS_FRAME_IS_NOT_COMPLETE(status) \
  (0 != ((status) & NS_FRAME_NOT_COMPLETE))

#define NS_FRAME_OVERFLOW_IS_INCOMPLETE(status) \
  (0 != ((status) & NS_FRAME_OVERFLOW_INCOMPLETE))

#define NS_FRAME_IS_FULLY_COMPLETE(status) \
  (NS_FRAME_IS_COMPLETE(status) && !NS_FRAME_OVERFLOW_IS_INCOMPLETE(status))

// These macros set or switch incomplete statuses without touching the
// NS_FRAME_REFLOW_NEXTINFLOW bit.
#define NS_FRAME_SET_INCOMPLETE(status) \
  status = (status & ~NS_FRAME_OVERFLOW_INCOMPLETE) | NS_FRAME_NOT_COMPLETE

#define NS_FRAME_SET_OVERFLOW_INCOMPLETE(status) \
  status = (status & ~NS_FRAME_NOT_COMPLETE) | NS_FRAME_OVERFLOW_INCOMPLETE

// This bit is set, when a break is requested. This bit is orthogonal
// to the nsIFrame::nsReflowStatus completion bits.
#define NS_INLINE_BREAK              0x0100

// When a break is requested, this bit when set indicates that the
// break should occur after the frame just reflowed; when the bit is
// clear the break should occur before the frame just reflowed.
#define NS_INLINE_BREAK_BEFORE       0x0000
#define NS_INLINE_BREAK_AFTER        0x0200

// The type of break requested can be found in these bits.
#define NS_INLINE_BREAK_TYPE_MASK    0xF000

// Set when a break was induced by completion of a first-letter
#define NS_INLINE_BREAK_FIRST_LETTER_COMPLETE 0x10000

//----------------------------------------
// Macros that use those bits

#define NS_INLINE_IS_BREAK(_status) \
  (0 != ((_status) & NS_INLINE_BREAK))

#define NS_INLINE_IS_BREAK_AFTER(_status) \
  (0 != ((_status) & NS_INLINE_BREAK_AFTER))

#define NS_INLINE_IS_BREAK_BEFORE(_status) \
  (NS_INLINE_BREAK == ((_status) & (NS_INLINE_BREAK|NS_INLINE_BREAK_AFTER)))

#define NS_INLINE_GET_BREAK_TYPE(_status) \
  (static_cast<StyleClear>(((_status) >> 12) & 0xF))

#define NS_INLINE_MAKE_BREAK_TYPE(_type)  (static_cast<int>(_type) << 12)

// Construct a line-break-before status. Note that there is no
// completion status for a line-break before because we *know* that
// the frame will be reflowed later and hence its current completion
// status doesn't matter.
#define NS_INLINE_LINE_BREAK_BEFORE()                                   \
  (NS_INLINE_BREAK | NS_INLINE_BREAK_BEFORE |                           \
   NS_INLINE_MAKE_BREAK_TYPE(StyleClear::Line))

// Take a completion status and add to it the desire to have a
// line-break after. For this macro we do need the completion status
// because the user of the status will need to know whether to
// continue the frame or not.
#define NS_INLINE_LINE_BREAK_AFTER(_completionStatus)                   \
  ((_completionStatus) | NS_INLINE_BREAK | NS_INLINE_BREAK_AFTER |      \
   NS_INLINE_MAKE_BREAK_TYPE(StyleClear::Line))

// A frame is "truncated" if the part of the frame before the first
// possible break point was unable to fit in the available vertical
// space.  Therefore, the entire frame should be moved to the next page.
// A frame that begins at the top of the page must never be "truncated".
// Doing so would likely cause an infinite loop.
#define NS_FRAME_TRUNCATED  0x0010
#define NS_FRAME_IS_TRUNCATED(status) \
  (0 != ((status) & NS_FRAME_TRUNCATED))
#define NS_FRAME_SET_TRUNCATION(status, aReflowInput, aMetrics) \
  aReflowInput.SetTruncated(aMetrics, &status);

// Merge the incompleteness, truncation and NS_FRAME_REFLOW_NEXTINFLOW
// status from aSecondary into aPrimary.
void NS_MergeReflowStatusInto(nsReflowStatus* aPrimary,
                              nsReflowStatus aSecondary);

//----------------------------------------------------------------------

/**
 * DidReflow status values.
 */
enum class nsDidReflowStatus : uint32_t {
  NOT_FINISHED,
  FINISHED
};

/**
 * When there is no scrollable overflow rect, the visual overflow rect
 * may be stored as four 1-byte deltas each strictly LESS THAN 0xff, for
 * the four edges of the rectangle, or the four bytes may be read as a
 * single 32-bit "overflow-rect type" value including at least one 0xff
 * byte as an indicator that the value does NOT represent four deltas.
 * If all four deltas are zero, this means that no overflow rect has
 * actually been set (this is the initial state of newly-created frames).
 */
#define NS_FRAME_OVERFLOW_DELTA_MAX     0xfe // max delta we can store

#define NS_FRAME_OVERFLOW_NONE    0x00000000 // there are no overflow rects;
                                             // code relies on this being
                                             // the all-zero value

#define NS_FRAME_OVERFLOW_LARGE   0x000000ff // overflow is stored as a
                                             // separate rect property

/**
 * nsBidiLevel is the type of the level values in our Unicode Bidi
 * implementation.
 * It holds an embedding level and indicates the visual direction
 * by its bit 0 (even/odd value).<p>
 *
 * <li><code>aParaLevel</code> can be set to the
 * pseudo-level values <code>NSBIDI_DEFAULT_LTR</code>
 * and <code>NSBIDI_DEFAULT_RTL</code>.</li></ul>
 *
 * @see nsBidi::SetPara
 *
 * <p>The related constants are not real, valid level values.
 * <code>NSBIDI_DEFAULT_XXX</code> can be used to specify
 * a default for the paragraph level for
 * when the <code>SetPara</code> function
 * shall determine it but there is no
 * strongly typed character in the input.<p>
 *
 * Note that the value for <code>NSBIDI_DEFAULT_LTR</code> is even
 * and the one for <code>NSBIDI_DEFAULT_RTL</code> is odd,
 * just like with normal LTR and RTL level values -
 * these special values are designed that way. Also, the implementation
 * assumes that NSBIDI_MAX_EXPLICIT_LEVEL is odd.
 *
 * @see NSBIDI_DEFAULT_LTR
 * @see NSBIDI_DEFAULT_RTL
 * @see NSBIDI_LEVEL_OVERRIDE
 * @see NSBIDI_MAX_EXPLICIT_LEVEL
 */
typedef uint8_t nsBidiLevel;

/** Paragraph level setting.
 *  If there is no strong character, then set the paragraph level to 0 (left-to-right).
 */
#define NSBIDI_DEFAULT_LTR 0xfe

/** Paragraph level setting.
 *  If there is no strong character, then set the paragraph level to 1 (right-to-left).
 */
#define NSBIDI_DEFAULT_RTL 0xff

/**
 * Maximum explicit embedding level.
 * (The maximum resolved level can be up to <code>NSBIDI_MAX_EXPLICIT_LEVEL+1</code>).
 *
 */
#define NSBIDI_MAX_EXPLICIT_LEVEL 125

/** Bit flag for level input.
 *  Overrides directional properties.
 */
#define NSBIDI_LEVEL_OVERRIDE 0x80

/**
 * <code>nsBidiDirection</code> values indicate the text direction.
 */
enum nsBidiDirection {
  /** All left-to-right text This is a 0 value. */
  NSBIDI_LTR,
  /** All right-to-left text This is a 1 value. */
  NSBIDI_RTL,
  /** Mixed-directional text. */
  NSBIDI_MIXED
};

namespace mozilla {

// https://drafts.csswg.org/css-align-3/#baseline-sharing-group
enum BaselineSharingGroup
{
  // NOTE Used as an array index so must be 0 and 1.
  eFirst = 0,
  eLast = 1,
};

// Loosely: https://drafts.csswg.org/css-align-3/#shared-alignment-context
enum class AlignmentContext
{
  eInline,
  eTable,
  eFlexbox,
  eGrid,
};

/*
 * For replaced elements only. Gets the intrinsic dimensions of this element.
 * The dimensions may only be one of the following two types:
 *
 *   eStyleUnit_Coord   - a length in app units
 *   eStyleUnit_None    - the element has no intrinsic size in this dimension
 */
struct IntrinsicSize {
  nsStyleCoord width, height;

  IntrinsicSize()
    : width(eStyleUnit_None), height(eStyleUnit_None)
  {}
  IntrinsicSize(const IntrinsicSize& rhs)
    : width(rhs.width), height(rhs.height)
  {}
  IntrinsicSize& operator=(const IntrinsicSize& rhs) {
    width = rhs.width; height = rhs.height; return *this;
  }
  bool operator==(const IntrinsicSize& rhs) {
    return width == rhs.width && height == rhs.height;
  }
  bool operator!=(const IntrinsicSize& rhs) {
    return !(*this == rhs);
  }
};

// Pseudo bidi embedding level indicating nonexistence.
static const nsBidiLevel kBidiLevelNone = 0xff;

struct FrameBidiData
{
  nsBidiLevel baseLevel;
  nsBidiLevel embeddingLevel;
  // The embedding level of virtual bidi formatting character before
  // this frame if any. kBidiLevelNone is used to indicate nonexistence
  // or unnecessity of such virtual character.
  nsBidiLevel precedingControl;
};

} // namespace mozilla

/// Generic destructor for frame properties. Calls delete.
template<typename T>
static void DeleteValue(T* aPropertyValue)
{
  delete aPropertyValue;
}

/// Generic destructor for frame properties. Calls Release().
template<typename T>
static void ReleaseValue(T* aPropertyValue)
{
  aPropertyValue->Release();
}

//----------------------------------------------------------------------

/**
 * A frame in the layout model. This interface is supported by all frame
 * objects.
 *
 * Frames can have multiple child lists: the default child list
 * (referred to as the <i>principal</i> child list, and additional named
 * child lists. There is an ordering of frames within a child list, but
 * there is no order defined between frames in different child lists of
 * the same parent frame.
 *
 * Frames are NOT reference counted. Use the Destroy() member function
 * to destroy a frame. The lifetime of the frame hierarchy is bounded by the
 * lifetime of the presentation shell which owns the frames.
 *
 * nsIFrame is a private Gecko interface. If you are not Gecko then you
 * should not use it. If you're not in layout, then you won't be able to
 * link to many of the functions defined here. Too bad.
 *
 * If you're not in layout but you must call functions in here, at least
 * restrict yourself to calling virtual methods, which won't hurt you as badly.
 */
class nsIFrame : public nsQueryFrame
{
public:
  using AlignmentContext = mozilla::AlignmentContext;
  using BaselineSharingGroup = mozilla::BaselineSharingGroup;
  template <typename T> using Maybe = mozilla::Maybe<T>;
  using Nothing = mozilla::Nothing;
  using OnNonvisible = mozilla::OnNonvisible;
  template<typename T=void>
  using PropertyDescriptor = const mozilla::FramePropertyDescriptor<T>*;
  using ReflowInput = mozilla::ReflowInput;
  using ReflowOutput = mozilla::ReflowOutput;
  using Visibility = mozilla::Visibility;

  typedef mozilla::FrameProperties FrameProperties;
  typedef mozilla::layers::Layer Layer;
  typedef mozilla::layout::FrameChildList ChildList;
  typedef mozilla::layout::FrameChildListID ChildListID;
  typedef mozilla::layout::FrameChildListIDs ChildListIDs;
  typedef mozilla::layout::FrameChildListIterator ChildListIterator;
  typedef mozilla::layout::FrameChildListArrayIterator ChildListArrayIterator;
  typedef mozilla::gfx::DrawTarget DrawTarget;
  typedef mozilla::gfx::Matrix Matrix;
  typedef mozilla::gfx::Matrix4x4 Matrix4x4;
  typedef mozilla::Sides Sides;
  typedef mozilla::LogicalSides LogicalSides;

  NS_DECL_QUERYFRAME_TARGET(nsIFrame)

  nsPresContext* PresContext() const {
    return StyleContext()->PresContext();
  }

  /**
   * Called to initialize the frame. This is called immediately after creating
   * the frame.
   *
   * If the frame is a continuing frame, then aPrevInFlow indicates the previous
   * frame (the frame that was split).
   *
   * If you want a view associated with your frame, you should create the view
   * after Init() has returned.
   *
   * @param   aContent the content object associated with the frame
   * @param   aParent the parent frame
   * @param   aPrevInFlow the prev-in-flow frame
   */
  virtual void Init(nsIContent*       aContent,
                    nsContainerFrame* aParent,
                    nsIFrame*         aPrevInFlow) = 0;

  /**
   * Destroys this frame and each of its child frames (recursively calls
   * Destroy() for each child). If this frame is a first-continuation, this
   * also removes the frame from the primary frame map and clears undisplayed
   * content for its content node.
   * If the frame is a placeholder, it also ensures the out-of-flow frame's
   * removal and destruction.
   */
  void Destroy() { DestroyFrom(this); }
 
  /** Flags for PeekOffsetCharacter, PeekOffsetNoAmount, PeekOffsetWord return values.
    */
  enum FrameSearchResult {
    // Peek found a appropriate offset within frame.
    FOUND = 0x00,
    // try next frame for offset.
    CONTINUE = 0x1,
    // offset not found because the frame was empty of text.
    CONTINUE_EMPTY = 0x2 | CONTINUE,
    // offset not found because the frame didn't contain any text that could be selected.
    CONTINUE_UNSELECTABLE = 0x4 | CONTINUE,
  };

protected:
  /**
   * Return true if the frame is part of a Selection.
   * Helper method to implement the public IsSelected() API.
   */
  virtual bool IsFrameSelected() const;

  /**
   * Implements Destroy(). Do not call this directly except from within a
   * DestroyFrom() implementation.
   *
   * @note This will always be called, so it is not necessary to override
   *       Destroy() in subclasses of nsFrame, just DestroyFrom().
   *
   * @param  aDestructRoot is the root of the subtree being destroyed
   */
  virtual void DestroyFrom(nsIFrame* aDestructRoot) = 0;
  friend class nsFrameList; // needed to pass aDestructRoot through to children
  friend class nsLineBox;   // needed to pass aDestructRoot through to children
  friend class nsContainerFrame; // needed to pass aDestructRoot through to children
  friend class nsFrame; // need to assign mParent
public:

  /**
   * Get the content object associated with this frame. Does not add a reference.
   */
  nsIContent* GetContent() const { return mContent; }

  /**
   * Get the frame that should be the parent for the frames of child elements
   * May return nullptr during reflow
   */
  virtual nsContainerFrame* GetContentInsertionFrame() { return nullptr; }

  /**
   * Move any frames on our overflow list to the end of our principal list.
   * @return true if there were any overflow frames
   */
  virtual bool DrainSelfOverflowList() { return false; }

  /**
   * Get the frame that should be scrolled if the content associated
   * with this frame is targeted for scrolling. For frames implementing
   * nsIScrollableFrame this will return the frame itself. For frames
   * like nsTextControlFrame that contain a scrollframe, will return
   * that scrollframe.
   */
  virtual nsIScrollableFrame* GetScrollTargetFrame() { return nullptr; }

  /**
   * Get the offsets of the frame. most will be 0,0
   *
   */
  virtual nsresult GetOffsets(int32_t &start, int32_t &end) const = 0;

  /**
   * Reset the offsets when splitting frames during Bidi reordering
   *
   */
  virtual void AdjustOffsetsForBidi(int32_t aStart, int32_t aEnd) {}

  /**
   * Get the style context associated with this frame.
   */
  nsStyleContext* StyleContext() const { return mStyleContext; }
  void SetStyleContext(nsStyleContext* aContext)
  { 
    if (aContext != mStyleContext) {
      nsStyleContext* oldStyleContext = mStyleContext;
      mStyleContext = aContext;
      aContext->AddRef();
#ifdef DEBUG
      aContext->FrameAddRef();
#endif
      DidSetStyleContext(oldStyleContext);
#ifdef DEBUG
      oldStyleContext->FrameRelease();
#endif
      oldStyleContext->Release();
    }
  }

  /**
   * SetStyleContextWithoutNotification is for changes to the style
   * context that should suppress style change processing, in other
   * words, those that aren't really changes.  This generally means only
   * changes that happen during frame construction.
   */
  void SetStyleContextWithoutNotification(nsStyleContext* aContext)
  {
    if (aContext != mStyleContext) {
#ifdef DEBUG
      mStyleContext->FrameRelease();
#endif
      mStyleContext->Release();
      mStyleContext = aContext;
      aContext->AddRef();
#ifdef DEBUG
      aContext->FrameAddRef();
#endif
    }
  }

  // Style post processing hook
  // Attention: the old style context is the one we're forgetting,
  // and hence possibly completely bogus for GetStyle* purposes.
  // Use PeekStyleData instead.
  virtual void DidSetStyleContext(nsStyleContext* aOldStyleContext) = 0;

  /**
   * Define typesafe getter functions for each style struct by
   * preprocessing the list of style structs.  These functions are the
   * preferred way to get style data.  The macro creates functions like:
   *   const nsStyleBorder* StyleBorder();
   *   const nsStyleColor* StyleColor();
   *
   * Callers outside of libxul should use nsIDOMWindow::GetComputedStyle()
   * instead of these accessors.
   */
  #define STYLE_STRUCT(name_, checkdata_cb_)                                  \
    const nsStyle##name_ * Style##name_ () const {                            \
      NS_ASSERTION(mStyleContext, "No style context found!");                 \
      return mStyleContext->Style##name_ ();                                  \
    }
  #include "nsStyleStructList.h"
  #undef STYLE_STRUCT

  /** Also forward GetVisitedDependentColor to the style context */
  nscolor GetVisitedDependentColor(nsCSSPropertyID aProperty)
    { return mStyleContext->GetVisitedDependentColor(aProperty); }

  /**
   * These methods are to access any additional style contexts that
   * the frame may be holding. These are contexts that are children
   * of the frame's primary context and are NOT used as style contexts
   * for any child frames. These contexts also MUST NOT have any child 
   * contexts whatsoever. If you need to insert style contexts into the
   * style tree, then you should create pseudo element frames to own them
   * The indicies must be consecutive and implementations MUST return an 
   * NS_ERROR_INVALID_ARG if asked for an index that is out of range.
   */
  virtual nsStyleContext* GetAdditionalStyleContext(int32_t aIndex) const = 0;

  virtual void SetAdditionalStyleContext(int32_t aIndex,
                                         nsStyleContext* aStyleContext) = 0;

  /**
   * Accessor functions for geometric parent.
   */
  nsContainerFrame* GetParent() const { return mParent; }

  /**
   * Gets the parent of a frame, using the parent of the placeholder for
   * out-of-flow frames.
   */
  inline nsContainerFrame* GetInFlowParent();

  /**
   * Set this frame's parent to aParent.
   * If the frame may have moved into or out of a scrollframe's
   * frame subtree, StickyScrollContainer::NotifyReparentedFrameAcrossScrollFrameBoundary
   * must also be called.
   */
  void SetParent(nsContainerFrame* aParent);

  /**
   * The frame's writing-mode, used for logical layout computations.
   */
  virtual mozilla::WritingMode GetWritingMode() const {
    return mozilla::WritingMode(StyleContext());
  }

  /**
   * Get the writing mode of this frame, but if it is styled with
   * unicode-bidi: plaintext, reset the direction to the resolved paragraph
   * level of the given subframe (typically the first frame on the line),
   * not this frame's writing mode, because the container frame could be split
   * by hard line breaks into multiple paragraphs with different base direction.
   */
  mozilla::WritingMode GetWritingMode(nsIFrame* aSubFrame) const;

  /**
   * Bounding rect of the frame. The values are in app units, and the origin is
   * relative to the upper-left of the geometric parent. The size includes the
   * content area, borders, and padding.
   *
   * Note: moving or sizing the frame does not affect the view's size or
   * position.
   */
  nsRect GetRect() const { return mRect; }
  nsPoint GetPosition() const { return mRect.TopLeft(); }
  nsSize GetSize() const { return mRect.Size(); }
  nsRect GetRectRelativeToSelf() const {
    return nsRect(nsPoint(0, 0), mRect.Size());
  }
  /**
   * Dimensions and position in logical coordinates in the frame's writing mode
   *  or another writing mode
   */
  mozilla::LogicalRect GetLogicalRect(const nsSize& aContainerSize) const {
    return GetLogicalRect(GetWritingMode(), aContainerSize);
  }
  mozilla::LogicalPoint GetLogicalPosition(const nsSize& aContainerSize) const {
    return GetLogicalPosition(GetWritingMode(), aContainerSize);
  }
  mozilla::LogicalSize GetLogicalSize() const {
    return GetLogicalSize(GetWritingMode());
  }
  mozilla::LogicalRect GetLogicalRect(mozilla::WritingMode aWritingMode,
                                      const nsSize& aContainerSize) const {
    return mozilla::LogicalRect(aWritingMode, GetRect(), aContainerSize);
  }
  mozilla::LogicalPoint GetLogicalPosition(mozilla::WritingMode aWritingMode,
                                           const nsSize& aContainerSize) const {
    return GetLogicalRect(aWritingMode, aContainerSize).Origin(aWritingMode);
  }
  mozilla::LogicalSize GetLogicalSize(mozilla::WritingMode aWritingMode) const {
    return mozilla::LogicalSize(aWritingMode, GetSize());
  }
  nscoord IStart(const nsSize& aContainerSize) const {
    return IStart(GetWritingMode(), aContainerSize);
  }
  nscoord IStart(mozilla::WritingMode aWritingMode,
                 const nsSize& aContainerSize) const {
    return GetLogicalPosition(aWritingMode, aContainerSize).I(aWritingMode);
  }
  nscoord BStart(const nsSize& aContainerSize) const {
    return BStart(GetWritingMode(), aContainerSize);
  }
  nscoord BStart(mozilla::WritingMode aWritingMode,
                 const nsSize& aContainerSize) const {
    return GetLogicalPosition(aWritingMode, aContainerSize).B(aWritingMode);
  }
  nscoord ISize() const { return ISize(GetWritingMode()); }
  nscoord ISize(mozilla::WritingMode aWritingMode) const {
    return GetLogicalSize(aWritingMode).ISize(aWritingMode);
  }
  nscoord BSize() const { return BSize(GetWritingMode()); }
  nscoord BSize(mozilla::WritingMode aWritingMode) const {
    return GetLogicalSize(aWritingMode).BSize(aWritingMode);
  }
  nscoord ContentBSize() const { return ContentBSize(GetWritingMode()); }
  nscoord ContentBSize(mozilla::WritingMode aWritingMode) const {
    auto bp = GetLogicalUsedBorderAndPadding(aWritingMode);
    bp.ApplySkipSides(GetLogicalSkipSides());
    return std::max(0, BSize(aWritingMode) - bp.BStartEnd(aWritingMode));
  }

  /**
   * When we change the size of the frame's border-box rect, we may need to
   * reset the overflow rect if it was previously stored as deltas.
   * (If it is currently a "large" overflow and could be re-packed as deltas,
   * we don't bother as the cost of the allocation has already been paid.)
   */
  void SetRect(const nsRect& aRect) {
    if (mOverflow.mType != NS_FRAME_OVERFLOW_LARGE &&
        mOverflow.mType != NS_FRAME_OVERFLOW_NONE) {
      nsOverflowAreas overflow = GetOverflowAreas();
      mRect = aRect;
      SetOverflowAreas(overflow);
    } else {
      mRect = aRect;
    }
  }
  /**
   * Set this frame's rect from a logical rect in its own writing direction
   */
  void SetRect(const mozilla::LogicalRect& aRect,
               const nsSize& aContainerSize) {
    SetRect(GetWritingMode(), aRect, aContainerSize);
  }
  /**
   * Set this frame's rect from a logical rect in a different writing direction
   * (GetPhysicalRect will assert if the writing mode doesn't match)
   */
  void SetRect(mozilla::WritingMode aWritingMode,
               const mozilla::LogicalRect& aRect,
               const nsSize& aContainerSize) {
    SetRect(aRect.GetPhysicalRect(aWritingMode, aContainerSize));
  }

  /**
   * Set this frame's size from a logical size in its own writing direction.
   * This leaves the frame's logical position unchanged, which means its
   * physical position may change (for right-to-left modes).
   */
  void SetSize(const mozilla::LogicalSize& aSize) {
    SetSize(GetWritingMode(), aSize);
  }
  /*
   * Set this frame's size from a logical size in a different writing direction.
   * This leaves the frame's logical position in the given mode unchanged,
   * which means its physical position may change (for right-to-left modes).
   */
  void SetSize(mozilla::WritingMode aWritingMode,
               const mozilla::LogicalSize& aSize)
  {
    if ((!aWritingMode.IsVertical() && !aWritingMode.IsBidiLTR()) ||
        aWritingMode.IsVerticalRL()) {
      nscoord oldWidth = mRect.width;
      SetSize(aSize.GetPhysicalSize(aWritingMode));
      mRect.x -= mRect.width - oldWidth;
    } else {
      SetSize(aSize.GetPhysicalSize(aWritingMode));
    }
  }

  /**
   * Set this frame's physical size. This leaves the frame's physical position
   * (topLeft) unchanged.
   */
  void SetSize(const nsSize& aSize) {
    SetRect(nsRect(mRect.TopLeft(), aSize));
  }

  void SetPosition(const nsPoint& aPt) { mRect.MoveTo(aPt); }
  void SetPosition(mozilla::WritingMode aWritingMode,
                   const mozilla::LogicalPoint& aPt,
                   const nsSize& aContainerSize) {
    // We subtract mRect.Size() from the container size to account for
    // the fact that logical origins in RTL coordinate systems are at
    // the top right of the frame instead of the top left.
    mRect.MoveTo(aPt.GetPhysicalPoint(aWritingMode,
                                      aContainerSize - mRect.Size()));
  }

  /**
   * Move the frame, accounting for relative positioning. Use this when
   * adjusting the frame's position by a known amount, to properly update its
   * saved normal position (see GetNormalPosition below).
   *
   * This must be used only when moving a frame *after*
   * ReflowInput::ApplyRelativePositioning is called.  When moving
   * a frame during the reflow process prior to calling
   * ReflowInput::ApplyRelativePositioning, the position should
   * simply be adjusted directly (e.g., using SetPosition()).
   */
  void MovePositionBy(const nsPoint& aTranslation);

  /**
   * As above, using a logical-point delta in a given writing mode.
   */
  void MovePositionBy(mozilla::WritingMode aWritingMode,
                      const mozilla::LogicalPoint& aTranslation)
  {
    // The LogicalPoint represents a vector rather than a point within a
    // rectangular coordinate space, so we use a null containerSize when
    // converting logical to physical.
    const nsSize nullContainerSize;
    MovePositionBy(aTranslation.GetPhysicalPoint(aWritingMode,
                                                 nullContainerSize));
  }

  /**
   * Return frame's rect without relative positioning
   */
  nsRect GetNormalRect() const;

  /**
   * Return frame's position without relative positioning
   */
  nsPoint GetNormalPosition() const;
  mozilla::LogicalPoint
  GetLogicalNormalPosition(mozilla::WritingMode aWritingMode,
                           const nsSize& aContainerSize) const
  {
    // Subtract the size of this frame from the container size to get
    // the correct position in rtl frames where the origin is on the
    // right instead of the left
    return mozilla::LogicalPoint(aWritingMode,
                                 GetNormalPosition(),
                                 aContainerSize - mRect.Size());
  }

  virtual nsPoint GetPositionOfChildIgnoringScrolling(nsIFrame* aChild)
  { return aChild->GetPosition(); }
  
  nsPoint GetPositionIgnoringScrolling();

  typedef AutoTArray<nsIContent*, 2> ContentArray;
  static void DestroyContentArray(ContentArray* aArray);

#define NS_DECLARE_FRAME_PROPERTY_WITH_DTOR(prop, type, dtor)             \
  static const mozilla::FramePropertyDescriptor<type>* prop() {           \
    /* Use of constexpr caused startup crashes with MSVC2015u1 PGO. */    \
    static const auto descriptor =                                        \
      mozilla::FramePropertyDescriptor<type>::NewWithDestructor<dtor>();  \
    return &descriptor;                                                   \
  }

// Don't use this unless you really know what you're doing!
#define NS_DECLARE_FRAME_PROPERTY_WITH_FRAME_IN_DTOR(prop, type, dtor)    \
  static const mozilla::FramePropertyDescriptor<type>* prop() {           \
    /* Use of constexpr caused startup crashes with MSVC2015u1 PGO. */    \
    static const auto descriptor = mozilla::                              \
      FramePropertyDescriptor<type>::NewWithDestructorWithFrame<dtor>();  \
    return &descriptor;                                                   \
  }

#define NS_DECLARE_FRAME_PROPERTY_WITHOUT_DTOR(prop, type)                \
  static const mozilla::FramePropertyDescriptor<type>* prop() {           \
    /* Use of constexpr caused startup crashes with MSVC2015u1 PGO. */    \
    static const auto descriptor =                                        \
      mozilla::FramePropertyDescriptor<type>::NewWithoutDestructor();     \
    return &descriptor;                                                   \
  }

#define NS_DECLARE_FRAME_PROPERTY_DELETABLE(prop, type) \
  NS_DECLARE_FRAME_PROPERTY_WITH_DTOR(prop, type, DeleteValue)

#define NS_DECLARE_FRAME_PROPERTY_RELEASABLE(prop, type) \
  NS_DECLARE_FRAME_PROPERTY_WITH_DTOR(prop, type, ReleaseValue)

#define NS_DECLARE_FRAME_PROPERTY_WITH_DTOR_NEVER_CALLED(prop, type)  \
  static void AssertOnDestroyingProperty##prop(type*) {               \
    MOZ_ASSERT_UNREACHABLE("Frame property " #prop " should never "   \
                           "be destroyed by the FrameProperties class"); \
  }                                                                   \
  NS_DECLARE_FRAME_PROPERTY_WITH_DTOR(prop, type,                     \
                                      AssertOnDestroyingProperty##prop)

#define NS_DECLARE_FRAME_PROPERTY_SMALL_VALUE(prop, type) \
  NS_DECLARE_FRAME_PROPERTY_WITHOUT_DTOR(prop, mozilla::SmallValueHolder<type>)

  NS_DECLARE_FRAME_PROPERTY_WITHOUT_DTOR(IBSplitSibling, nsContainerFrame)
  NS_DECLARE_FRAME_PROPERTY_WITHOUT_DTOR(IBSplitPrevSibling, nsContainerFrame)

  NS_DECLARE_FRAME_PROPERTY_DELETABLE(NormalPositionProperty, nsPoint)
  NS_DECLARE_FRAME_PROPERTY_DELETABLE(ComputedOffsetProperty, nsMargin)

  NS_DECLARE_FRAME_PROPERTY_DELETABLE(OutlineInnerRectProperty, nsRect)
  NS_DECLARE_FRAME_PROPERTY_DELETABLE(PreEffectsBBoxProperty, nsRect)
  NS_DECLARE_FRAME_PROPERTY_DELETABLE(PreTransformOverflowAreasProperty,
                                      nsOverflowAreas)

  // The initial overflow area passed to FinishAndStoreOverflow. This is only set
  // on frames that Preserve3D() or HasPerspective() or IsTransformed(), and
  // when at least one of the overflow areas differs from the frame bound rect.
  NS_DECLARE_FRAME_PROPERTY_DELETABLE(InitialOverflowProperty, nsOverflowAreas)

#ifdef DEBUG
  // InitialOverflowPropertyDebug is added to the frame to indicate that either
  // the InitialOverflowProperty has been stored or the InitialOverflowProperty
  // has been suppressed due to being set to the default value (frame bounds)
  NS_DECLARE_FRAME_PROPERTY_SMALL_VALUE(DebugInitialOverflowPropertyApplied, bool)
#endif

  NS_DECLARE_FRAME_PROPERTY_DELETABLE(UsedMarginProperty, nsMargin)
  NS_DECLARE_FRAME_PROPERTY_DELETABLE(UsedPaddingProperty, nsMargin)
  NS_DECLARE_FRAME_PROPERTY_DELETABLE(UsedBorderProperty, nsMargin)

  NS_DECLARE_FRAME_PROPERTY_SMALL_VALUE(LineBaselineOffset, nscoord)

  // Temporary override for a flex item's main-size property (either width
  // or height), imposed by its flex container.
  NS_DECLARE_FRAME_PROPERTY_SMALL_VALUE(FlexItemMainSizeOverride, nscoord)

  NS_DECLARE_FRAME_PROPERTY_RELEASABLE(CachedBackgroundImageDT, DrawTarget)

  NS_DECLARE_FRAME_PROPERTY_DELETABLE(InvalidationRect, nsRect)

  NS_DECLARE_FRAME_PROPERTY_SMALL_VALUE(RefusedAsyncAnimationProperty, bool)

  NS_DECLARE_FRAME_PROPERTY_SMALL_VALUE(FragStretchBSizeProperty, nscoord)

  // The block-axis margin-box size associated with eBClampMarginBoxMinSize.
  NS_DECLARE_FRAME_PROPERTY_SMALL_VALUE(BClampMarginBoxMinSizeProperty, nscoord)

  NS_DECLARE_FRAME_PROPERTY_SMALL_VALUE(IBaselinePadProperty, nscoord)
  NS_DECLARE_FRAME_PROPERTY_SMALL_VALUE(BBaselinePadProperty, nscoord)

  NS_DECLARE_FRAME_PROPERTY_WITH_DTOR(GenConProperty, ContentArray,
                                      DestroyContentArray)

  NS_DECLARE_FRAME_PROPERTY_SMALL_VALUE(BidiDataProperty, mozilla::FrameBidiData)

  mozilla::FrameBidiData GetBidiData()
  {
    return GetProperty(BidiDataProperty());
  }

  nsBidiLevel GetBaseLevel()
  {
    return GetBidiData().baseLevel;
  }

  nsBidiLevel GetEmbeddingLevel()
  {
    return GetBidiData().embeddingLevel;
  }

  nsTArray<nsIContent*>* GetGenConPseudos() {
    return GetProperty(GenConProperty());
  }

  /**
   * Return the distance between the border edge of the frame and the
   * margin edge of the frame.  Like GetRect(), returns the dimensions
   * as of the most recent reflow.
   *
   * This doesn't include any margin collapsing that may have occurred.
   *
   * It also treats 'auto' margins as zero, and treats any margins that
   * should have been turned into 'auto' because of overconstraint as
   * having their original values.
   */
  virtual nsMargin GetUsedMargin() const;
  virtual mozilla::LogicalMargin
  GetLogicalUsedMargin(mozilla::WritingMode aWritingMode) const {
    return mozilla::LogicalMargin(aWritingMode, GetUsedMargin());
  }

  /**
   * Return the distance between the border edge of the frame (which is
   * its rect) and the padding edge of the frame. Like GetRect(), returns
   * the dimensions as of the most recent reflow.
   *
   * Note that this differs from StyleBorder()->GetComputedBorder() in
   * that this describes a region of the frame's box, and
   * StyleBorder()->GetComputedBorder() describes a border.  They differ
   * for tables (particularly border-collapse tables) and themed
   * elements.
   */
  virtual nsMargin GetUsedBorder() const;
  virtual mozilla::LogicalMargin
  GetLogicalUsedBorder(mozilla::WritingMode aWritingMode) const {
    return mozilla::LogicalMargin(aWritingMode, GetUsedBorder());
  }

  /**
   * Return the distance between the padding edge of the frame and the
   * content edge of the frame.  Like GetRect(), returns the dimensions
   * as of the most recent reflow.
   */
  virtual nsMargin GetUsedPadding() const;
  virtual mozilla::LogicalMargin
  GetLogicalUsedPadding(mozilla::WritingMode aWritingMode) const {
    return mozilla::LogicalMargin(aWritingMode, GetUsedPadding());
  }

  nsMargin GetUsedBorderAndPadding() const {
    return GetUsedBorder() + GetUsedPadding();
  }
  mozilla::LogicalMargin
  GetLogicalUsedBorderAndPadding(mozilla::WritingMode aWritingMode) const {
    return mozilla::LogicalMargin(aWritingMode, GetUsedBorderAndPadding());
  }

  /**
   * Like the frame's rect (see |GetRect|), which is the border rect,
   * other rectangles of the frame, in app units, relative to the parent.
   */
  nsRect GetPaddingRect() const;
  nsRect GetPaddingRectRelativeToSelf() const;
  nsRect GetContentRect() const;
  nsRect GetContentRectRelativeToSelf() const;
  nsRect GetMarginRectRelativeToSelf() const;

  /**
   * The area to paint box-shadows around.  The default is the border rect.
   * (nsFieldSetFrame overrides this).
   */
  virtual nsRect VisualBorderRectRelativeToSelf() const {
    return nsRect(0, 0, mRect.width, mRect.height);
  }

  /**
   * Get the size, in app units, of the border radii. It returns FALSE iff all
   * returned radii == 0 (so no border radii), TRUE otherwise.
   * For the aRadii indexes, use the NS_CORNER_* constants in nsStyleConsts.h
   * If a side is skipped via aSkipSides, its corners are forced to 0.
   *
   * All corner radii are then adjusted so they do not require more
   * space than aBorderArea, according to the algorithm in css3-background.
   *
   * aFrameSize is used as the basis for percentage widths and heights.
   * aBorderArea is used for the adjustment of radii that might be too
   * large.
   * FIXME: In the long run, we can probably get away with only one of
   * these, especially if we change the way we handle outline-radius (by
   * removing it and inflating the border radius)
   *
   * Return whether any radii are nonzero.
   */
  static bool ComputeBorderRadii(const nsStyleCorners& aBorderRadius,
                                 const nsSize& aFrameSize,
                                 const nsSize& aBorderArea,
                                 Sides aSkipSides,
                                 nscoord aRadii[8]);

  /*
   * Given a set of border radii for one box (e.g., border box), convert
   * it to the equivalent set of radii for another box (e.g., in to
   * padding box, out to outline box) by reducing radii or increasing
   * nonzero radii as appropriate.
   *
   * Indices into aRadii are the NS_CORNER_* constants in nsStyleConsts.h
   *
   * Note that InsetBorderRadii is lossy, since it can turn nonzero
   * radii into zero, and OutsetBorderRadii does not inflate zero radii.
   * Therefore, callers should always inset or outset directly from the
   * original value coming from style.
   */
  static void InsetBorderRadii(nscoord aRadii[8], const nsMargin &aOffsets);
  static void OutsetBorderRadii(nscoord aRadii[8], const nsMargin &aOffsets);

  /**
   * Fill in border radii for this frame.  Return whether any are nonzero.
   * Indices into aRadii are the NS_CORNER_* constants in nsStyleConsts.h
   * aSkipSides is a union of SIDE_BIT_LEFT/RIGHT/TOP/BOTTOM bits that says
   * which side(s) to skip.
   */
  virtual bool GetBorderRadii(const nsSize& aFrameSize,
                              const nsSize& aBorderArea,
                              Sides aSkipSides,
                              nscoord aRadii[8]) const;
  bool GetBorderRadii(nscoord aRadii[8]) const;

  bool GetPaddingBoxBorderRadii(nscoord aRadii[8]) const;
  bool GetContentBoxBorderRadii(nscoord aRadii[8]) const;

  /**
   * XXX: this method will likely be replaced by GetVerticalAlignBaseline
   * Get the position of the frame's baseline, relative to the top of
   * the frame (its top border edge).  Only valid when Reflow is not
   * needed.
   * @note You should only call this on frames with a WM that's parallel to aWM.
   * @param aWM the writing-mode of the alignment context, with the ltr/rtl
   * direction tweak done by nsIFrame::GetWritingMode(nsIFrame*) in inline
   * contexts (see that method).
   */
  virtual nscoord GetLogicalBaseline(mozilla::WritingMode aWM) const = 0;

  /**
   * Synthesize a first(last) inline-axis baseline from our margin-box.
   * An alphabetical baseline is at the start(end) edge and a central baseline
   * is at the center of our block-axis margin-box (aWM tells which to use).
   * https://drafts.csswg.org/css-align-3/#synthesize-baselines
   * @note You should only call this on frames with a WM that's parallel to aWM.
   * @param aWM the writing-mode of the alignment context
   * @return an offset from our border-box block-axis start(end) edge for
   * a first(last) baseline respectively
   * (implemented in nsIFrameInlines.h)
   */
  inline nscoord SynthesizeBaselineBOffsetFromMarginBox(
                   mozilla::WritingMode aWM,
                   BaselineSharingGroup aGroup) const;

  /**
   * Synthesize a first(last) inline-axis baseline from our border-box.
   * An alphabetical baseline is at the start(end) edge and a central baseline
   * is at the center of our block-axis border-box (aWM tells which to use).
   * https://drafts.csswg.org/css-align-3/#synthesize-baselines
   * @note The returned value is only valid when reflow is not needed.
   * @note You should only call this on frames with a WM that's parallel to aWM.
   * @param aWM the writing-mode of the alignment context
   * @return an offset from our border-box block-axis start(end) edge for
   * a first(last) baseline respectively
   * (implemented in nsIFrameInlines.h)
   */
  inline nscoord SynthesizeBaselineBOffsetFromBorderBox(
                   mozilla::WritingMode aWM,
                   BaselineSharingGroup aGroup) const;

  /**
   * Return the position of the frame's inline-axis baseline, or synthesize one
   * for the given alignment context. The returned baseline is the distance from
   * the block-axis border-box start(end) edge for aBaselineGroup eFirst(eLast).
   * @note The returned value is only valid when reflow is not needed.
   * @note You should only call this on frames with a WM that's parallel to aWM.
   * @param aWM the writing-mode of the alignment context
   * @param aBaselineOffset out-param, only valid if the method returns true
   * (implemented in nsIFrameInlines.h)
   */
  inline nscoord BaselineBOffset(mozilla::WritingMode aWM,
                                 BaselineSharingGroup aBaselineGroup,
                                 AlignmentContext     aAlignmentContext) const;

  /**
   * XXX: this method is taking over the role that GetLogicalBaseline has.
   * Return true if the frame has a CSS2 'vertical-align' baseline.
   * If it has, then the returned baseline is the distance from the block-
   * axis border-box start edge.
   * @note This method should only be used in AlignmentContext::eInline contexts.
   * @note The returned value is only valid when reflow is not needed.
   * @note You should only call this on frames with a WM that's parallel to aWM.
   * @param aWM the writing-mode of the alignment context
   * @param aBaseline the baseline offset, only valid if the method returns true
   */
  virtual bool GetVerticalAlignBaseline(mozilla::WritingMode aWM,
                                        nscoord* aBaseline) const {
    return false;
  }

  /**
   * Return true if the frame has a first(last) inline-axis natural baseline per
   * CSS Box Alignment.  If so, then the returned baseline is the distance from
   * the block-axis border-box start(end) edge for aBaselineGroup eFirst(eLast).
   * https://drafts.csswg.org/css-align-3/#natural-baseline
   * @note The returned value is only valid when reflow is not needed.
   * @note You should only call this on frames with a WM that's parallel to aWM.
   * @param aWM the writing-mode of the alignment context
   * @param aBaseline the baseline offset, only valid if the method returns true
   */
  virtual bool GetNaturalBaselineBOffset(mozilla::WritingMode aWM,
                                         BaselineSharingGroup aBaselineGroup,
                                         nscoord*             aBaseline) const {
    return false;
  }

  /**
   * Get the position of the baseline on which the caret needs to be placed,
   * relative to the top of the frame.  This is mostly needed for frames
   * which return a baseline from GetBaseline which is not useful for
   * caret positioning.
   */
  virtual nscoord GetCaretBaseline() const {
    return GetLogicalBaseline(GetWritingMode());
  }

  ///////////////////////////////////////////////////////////////////////////////
  // The public visibility API.
  ///////////////////////////////////////////////////////////////////////////////

  /// @return true if we're tracking visibility for this frame.
  bool TrackingVisibility() const
  {
    return bool(GetStateBits() & NS_FRAME_VISIBILITY_IS_TRACKED);
  }

  /// @return the visibility state of this frame. See the Visibility enum
  /// for the possible return values and their meanings.
  Visibility GetVisibility() const;

  /// Update the visibility state of this frame synchronously.
  /// XXX(seth): Avoid using this method; we should be relying on the refresh
  /// driver for visibility updates. This method, which replaces
  /// nsLayoutUtils::UpdateApproximateFrameVisibility(), exists purely as a
  /// temporary measure to avoid changing behavior during the transition from
  /// the old image visibility code.
  void UpdateVisibilitySynchronously();

  // A frame property which stores the visibility state of this frame. Right
  // now that consists of an approximate visibility counter represented as a
  // uint32_t. When the visibility of this frame is not being tracked, this
  // property is absent.
  NS_DECLARE_FRAME_PROPERTY_SMALL_VALUE(VisibilityStateProperty, uint32_t);

protected:

  /**
   * Subclasses can call this method to enable visibility tracking for this frame.
   *
   * If visibility tracking was previously disabled, this will schedule an
   * update an asynchronous update of visibility.
   */
  void EnableVisibilityTracking();

  /**
   * Subclasses can call this method to disable visibility tracking for this frame.
   *
   * Note that if visibility tracking was previously enabled, disabling visibility
   * tracking will cause a synchronous call to OnVisibilityChange().
   */
  void DisableVisibilityTracking();

  /**
   * Called when a frame transitions between visibility states (for example,
   * from nonvisible to visible, or from visible to nonvisible).
   *
   * @param aNewVisibility    The new visibility state.
   * @param aNonvisibleAction A requested action if the frame has become
   *                          nonvisible. If Nothing(), no action is
   *                          requested. If DISCARD_IMAGES is specified, the
   *                          frame is requested to ask any images it's
   *                          associated with to discard their surfaces if
   *                          possible.
   *
   * Subclasses which override this method should call their parent class's
   * implementation.
   */
  virtual void OnVisibilityChange(Visibility aNewVisibility,
                                  Maybe<OnNonvisible> aNonvisibleAction = Nothing());

public:

  ///////////////////////////////////////////////////////////////////////////////
  // Internal implementation for the approximate frame visibility API.
  ///////////////////////////////////////////////////////////////////////////////

  /**
   * We track the approximate visibility of frames using a counter; if it's
   * non-zero, then the frame is considered visible. Using a counter allows us
   * to account for situations where the frame may be visible in more than one
   * place (for example, via -moz-element), and it simplifies the
   * implementation of our approximate visibility tracking algorithms.
   *
   * @param aNonvisibleAction A requested action if the frame has become
   *                          nonvisible. If Nothing(), no action is
   *                          requested. If DISCARD_IMAGES is specified, the
   *                          frame is requested to ask any images it's
   *                          associated with to discard their surfaces if
   *                          possible.
   */
  void DecApproximateVisibleCount(Maybe<OnNonvisible> aNonvisibleAction = Nothing());
  void IncApproximateVisibleCount();


  /**
   * Get the specified child list.
   *
   * @param   aListID identifies the requested child list.
   * @return  the child list.  If the requested list is unsupported by this
   *          frame type, an empty list will be returned.
   */
  virtual const nsFrameList& GetChildList(ChildListID aListID) const = 0;
  const nsFrameList& PrincipalChildList() const { return GetChildList(kPrincipalList); }
  virtual void GetChildLists(nsTArray<ChildList>* aLists) const = 0;

  /**
   * Gets the child lists for this frame, including
   * ones belong to a child document.
   */
  void GetCrossDocChildLists(nsTArray<ChildList>* aLists);

  // The individual concrete child lists.
  static const ChildListID kPrincipalList = mozilla::layout::kPrincipalList;
  static const ChildListID kAbsoluteList = mozilla::layout::kAbsoluteList;
  static const ChildListID kBulletList = mozilla::layout::kBulletList;
  static const ChildListID kCaptionList = mozilla::layout::kCaptionList;
  static const ChildListID kColGroupList = mozilla::layout::kColGroupList;
  static const ChildListID kExcessOverflowContainersList = mozilla::layout::kExcessOverflowContainersList;
  static const ChildListID kFixedList = mozilla::layout::kFixedList;
  static const ChildListID kFloatList = mozilla::layout::kFloatList;
  static const ChildListID kOverflowContainersList = mozilla::layout::kOverflowContainersList;
  static const ChildListID kOverflowList = mozilla::layout::kOverflowList;
  static const ChildListID kOverflowOutOfFlowList = mozilla::layout::kOverflowOutOfFlowList;
  static const ChildListID kPopupList = mozilla::layout::kPopupList;
  static const ChildListID kPushedFloatsList = mozilla::layout::kPushedFloatsList;
  static const ChildListID kSelectPopupList = mozilla::layout::kSelectPopupList;
  static const ChildListID kBackdropList = mozilla::layout::kBackdropList;
  // A special alias for kPrincipalList that do not request reflow.
  static const ChildListID kNoReflowPrincipalList = mozilla::layout::kNoReflowPrincipalList;

  /**
   * Child frames are linked together in a doubly-linked list
   */
  nsIFrame* GetNextSibling() const { return mNextSibling; }
  void SetNextSibling(nsIFrame* aNextSibling) {
    NS_ASSERTION(this != aNextSibling, "Creating a circular frame list, this is very bad.");
    if (mNextSibling && mNextSibling->GetPrevSibling() == this) {
      mNextSibling->mPrevSibling = nullptr;
    }
    mNextSibling = aNextSibling;
    if (mNextSibling) {
      mNextSibling->mPrevSibling = this;
    }
  }

  nsIFrame* GetPrevSibling() const { return mPrevSibling; }

  /**
   * Builds the display lists for the content represented by this frame
   * and its descendants. The background+borders of this element must
   * be added first, before any other content.
   * 
   * This should only be called by methods in nsFrame. Instead of calling this
   * directly, call either BuildDisplayListForStackingContext or
   * BuildDisplayListForChild.
   * 
   * See nsDisplayList.h for more information about display lists.
   * 
   * @param aDirtyRect content outside this rectangle can be ignored; the
   * rectangle is in frame coordinates
   */
  virtual void BuildDisplayList(nsDisplayListBuilder*   aBuilder,
                                const nsRect&           aDirtyRect,
                                const nsDisplayListSet& aLists) {}
  /**
   * Displays the caret onto the given display list builder. The caret is
   * painted on top of the rest of the display list items.
   *
   * @param aDirtyRect is the dirty rectangle that we're repainting.
   */
  void DisplayCaret(nsDisplayListBuilder* aBuilder,
                    const nsRect&         aDirtyRect,
                    nsDisplayList*        aList);

  /**
   * Get the preferred caret color at the offset.
   *
   * @param aOffset is offset of the content.
   */
  virtual nscolor GetCaretColorAt(int32_t aOffset);

 
  bool IsThemed(nsITheme::Transparency* aTransparencyState = nullptr) const {
    return IsThemed(StyleDisplay(), aTransparencyState);
  }
  bool IsThemed(const nsStyleDisplay* aDisp,
                  nsITheme::Transparency* aTransparencyState = nullptr) const {
    nsIFrame* mutable_this = const_cast<nsIFrame*>(this);
    if (!aDisp->mAppearance)
      return false;
    nsPresContext* pc = PresContext();
    nsITheme *theme = pc->GetTheme();
    if(!theme ||
       !theme->ThemeSupportsWidget(pc, mutable_this, aDisp->mAppearance))
      return false;
    if (aTransparencyState) {
      *aTransparencyState =
        theme->GetWidgetTransparency(mutable_this, aDisp->mAppearance);
    }
    return true;
  }
  
  /**
   * Builds a display list for the content represented by this frame,
   * treating this frame as the root of a stacking context.
   * @param aDirtyRect content outside this rectangle can be ignored; the
   * rectangle is in frame coordinates
   */
  void BuildDisplayListForStackingContext(nsDisplayListBuilder* aBuilder,
                                          const nsRect&         aDirtyRect,
                                          nsDisplayList*        aList);

  enum {
    DISPLAY_CHILD_FORCE_PSEUDO_STACKING_CONTEXT = 0x01,
    DISPLAY_CHILD_FORCE_STACKING_CONTEXT = 0x02,
    DISPLAY_CHILD_INLINE = 0x04
  };
  /**
   * Adjusts aDirtyRect for the child's offset, checks that the dirty rect
   * actually intersects the child (or its descendants), calls BuildDisplayList
   * on the child if necessary, and puts things in the right lists if the child
   * is positioned.
   *
   * @param aFlags combination of DISPLAY_CHILD_FORCE_PSEUDO_STACKING_CONTEXT,
   *    DISPLAY_CHILD_FORCE_STACKING_CONTEXT and DISPLAY_CHILD_INLINE
   */
  void BuildDisplayListForChild(nsDisplayListBuilder*   aBuilder,
                                nsIFrame*               aChild,
                                const nsRect&           aDirtyRect,
                                const nsDisplayListSet& aLists,
                                uint32_t                aFlags = 0);

  /**
   * Does this frame need a view?
   */
  virtual bool NeedsView() { return false; }

  bool RefusedAsyncAnimation() const
  {
    return GetProperty(RefusedAsyncAnimationProperty());
  }

  /**
   * Returns true if this frame is transformed (e.g. has CSS or SVG transforms)
   * or if its parent is an SVG frame that has children-only transforms (e.g.
   * an SVG viewBox attribute) or if its transform-style is preserve-3d or
   * the frame has transform animations.
   */
  bool IsTransformed() const;

  /**
   * Returns true if the frame is translucent or the frame has opacity
   * animations for the purposes of creating a stacking context.
   */
  bool HasOpacity() const
  {
    return HasOpacityInternal(1.0f);
  }
  /**
   * Returns true if the frame is translucent for display purposes.
   */
  bool HasVisualOpacity() const
  {
    // Treat an opacity value of 0.99 and above as opaque.  This is an
    // optimization aimed at Web content which use opacity:0.99 as a hint for
    // creating a stacking context only.
    return HasOpacityInternal(0.99f);
  }

   /**
   * Return true if this frame might be using a transform getter.
   */
  virtual bool HasTransformGetter() const { return false; }

  /**
   * Returns true if this frame is an SVG frame that has SVG transforms applied
   * to it, or if its parent frame is an SVG frame that has children-only
   * transforms (e.g. an SVG viewBox attribute).
   * If aOwnTransforms is non-null and the frame has its own SVG transforms,
   * aOwnTransforms will be set to these transforms. If aFromParentTransforms
   * is non-null and the frame has an SVG parent with children-only transforms,
   * then aFromParentTransforms will be set to these transforms.
   */
  virtual bool IsSVGTransformed(Matrix *aOwnTransforms = nullptr,
                                Matrix *aFromParentTransforms = nullptr) const;

  /**
   * Returns whether this frame will attempt to extend the 3d transforms of its
   * children. This requires transform-style: preserve-3d, as well as no clipping
   * or svg effects.
   */
  bool Extend3DContext() const;

  /**
   * Returns whether this frame has a parent that Extend3DContext() and has
   * its own transform (or hidden backface) to be combined with the parent's
   * transform.
   */
  bool Combines3DTransformWithAncestors() const;

  /**
   * Returns whether this frame has a hidden backface and has a parent that
   * Extend3DContext(). This is useful because in some cases the hidden
   * backface can safely be ignored if it could not be visible anyway.
   */
  bool In3DContextAndBackfaceIsHidden() const;

  bool IsPreserve3DLeaf() const {
    return Combines3DTransformWithAncestors() && !Extend3DContext();
  }

  bool HasPerspective() const;

  bool ChildrenHavePerspective() const;

  /**
   * Includes the overflow area of all descendants that participate in the current
   * 3d context into aOverflowAreas.
   */
  void ComputePreserve3DChildrenOverflow(nsOverflowAreas& aOverflowAreas);

  void RecomputePerspectiveChildrenOverflow(const nsIFrame* aStartFrame);

  /**
   * Returns the number of ancestors between this and the root of our frame tree
   */
  uint32_t GetDepthInFrameTree() const;

  /**
   * Event handling of GUI events.
   *
   * @param   aEvent event structure describing the type of event and rge widget
   *            where the event originated
   *          The |point| member of this is in the coordinate system of the
   *          view returned by GetOffsetFromView.
   * @param   aEventStatus a return value indicating whether the event was handled
   *            and whether default processing should be done
   *
   * XXX From a frame's perspective it's unclear what the effect of the event status
   * is. Does it cause the event to continue propagating through the frame hierarchy
   * or is it just returned to the widgets?
   *
   * @see     WidgetGUIEvent
   * @see     nsEventStatus
   */
  virtual nsresult  HandleEvent(nsPresContext* aPresContext,
                                mozilla::WidgetGUIEvent* aEvent,
                                nsEventStatus* aEventStatus) = 0;

  virtual nsresult  GetContentForEvent(mozilla::WidgetEvent* aEvent,
                                       nsIContent** aContent) = 0;

  // This structure keeps track of the content node and offsets associated with
  // a point; there is a primary and a secondary offset associated with any
  // point.  The primary and secondary offsets differ when the point is over a
  // non-text object.  The primary offset is the expected position of the
  // cursor calculated from a point; the secondary offset, when it is different,
  // indicates that the point is in the boundaries of some selectable object.
  // Note that the primary offset can be after the secondary offset; for places
  // that need the beginning and end of the object, the StartOffset and 
  // EndOffset helpers can be used.
  struct MOZ_STACK_CLASS ContentOffsets
  {
    ContentOffsets() : offset(0)
                     , secondaryOffset(0)
                     , associate(mozilla::CARET_ASSOCIATE_BEFORE) {}
    bool IsNull() { return !content; }
    // Helpers for places that need the ends of the offsets and expect them in
    // numerical order, as opposed to wanting the primary and secondary offsets
    int32_t StartOffset() { return std::min(offset, secondaryOffset); }
    int32_t EndOffset() { return std::max(offset, secondaryOffset); }

    nsCOMPtr<nsIContent> content;
    int32_t offset;
    int32_t secondaryOffset;
    // This value indicates whether the associated content is before or after
    // the offset; the most visible use is to allow the caret to know which line
    // to display on.
    mozilla::CaretAssociationHint associate;
  };
  enum {
    IGNORE_SELECTION_STYLE = 0x01,
    // Treat visibility:hidden frames as non-selectable
    SKIP_HIDDEN = 0x02
  };
  /**
   * This function calculates the content offsets for selection relative to
   * a point.  Note that this should generally only be callled on the event
   * frame associated with an event because this function does not account
   * for frame lists other than the primary one.
   * @param aPoint point relative to this frame
   */
  ContentOffsets GetContentOffsetsFromPoint(nsPoint aPoint,
                                            uint32_t aFlags = 0);

  virtual ContentOffsets GetContentOffsetsFromPointExternal(nsPoint aPoint,
                                                            uint32_t aFlags = 0)
  { return GetContentOffsetsFromPoint(aPoint, aFlags); }

  /**
   * Ensure that aImage gets notifed when the underlying image request loads
   * or animates.
   */
  void AssociateImage(const nsStyleImage& aImage, nsPresContext* aPresContext);

  /**
   * This structure holds information about a cursor. mContainer represents a
   * loaded image that should be preferred. If it is not possible to use it, or
   * if it is null, mCursor should be used.
   */
  struct MOZ_STACK_CLASS Cursor {
    nsCOMPtr<imgIContainer> mContainer;
    int32_t                 mCursor;
    bool                    mHaveHotspot;
    bool                    mLoading;
    float                   mHotspotX, mHotspotY;
  };
  /**
   * Get the cursor for a given frame.
   */
  virtual nsresult  GetCursor(const nsPoint&  aPoint,
                              Cursor&         aCursor) = 0;

  /**
   * Get a point (in the frame's coordinate space) given an offset into
   * the content. This point should be on the baseline of text with
   * the correct horizontal offset
   */
  virtual nsresult  GetPointFromOffset(int32_t                  inOffset,
                                       nsPoint*                 outPoint) = 0;

  /**
   * Get a list of character rects in a given range.
   * This is similar version of GetPointFromOffset.
   */
  virtual nsresult  GetCharacterRectsInRange(int32_t aInOffset,
                                             int32_t aLength,
                                             nsTArray<nsRect>& aRects) = 0;
  
  /**
   * Get the child frame of this frame which contains the given
   * content offset. outChildFrame may be this frame, or nullptr on return.
   * outContentOffset returns the content offset relative to the start
   * of the returned node. You can also pass a hint which tells the method
   * to stick to the end of the first found frame or the beginning of the 
   * next in case the offset falls on a boundary.
   */
  virtual nsresult GetChildFrameContainingOffset(int32_t    inContentOffset,
                                                 bool       inHint,//false stick left
                                                 int32_t*   outFrameContentOffset,
                                                 nsIFrame** outChildFrame) = 0;

 /**
   * Get the current frame-state value for this frame. aResult is
   * filled in with the state bits. 
   */
  nsFrameState GetStateBits() const { return mState; }

  /**
   * Update the current frame-state value for this frame. 
   */
  void AddStateBits(nsFrameState aBits) { mState |= aBits; }
  void RemoveStateBits(nsFrameState aBits) { mState &= ~aBits; }

  /**
   * Checks if the current frame-state includes all of the listed bits
   */
  bool HasAllStateBits(nsFrameState aBits) const
  {
    return (mState & aBits) == aBits;
  }
  
  /**
   * Checks if the current frame-state includes any of the listed bits
   */
  bool HasAnyStateBits(nsFrameState aBits) const
  {
    return mState & aBits;
  }

  /**
   * This call is invoked on the primary frame for a character data content
   * node, when it is changed in the content tree.
   */
  virtual nsresult  CharacterDataChanged(CharacterDataChangeInfo* aInfo) = 0;

  /**
   * This call is invoked when the value of a content objects's attribute
   * is changed. 
   * The first frame that maps that content is asked to deal
   * with the change by doing whatever is appropriate.
   *
   * @param aNameSpaceID the namespace of the attribute
   * @param aAttribute the atom name of the attribute
   * @param aModType Whether or not the attribute was added, changed, or removed.
   *   The constants are defined in nsIDOMMutationEvent.h.
   */
  virtual nsresult  AttributeChanged(int32_t         aNameSpaceID,
                                     nsIAtom*        aAttribute,
                                     int32_t         aModType) = 0;

  /**
   * When the content states of a content object change, this method is invoked
   * on the primary frame of that content object.
   *
   * @param aStates the changed states
   */
  virtual void ContentStatesChanged(mozilla::EventStates aStates);

  /**
   * Return how your frame can be split.
   */
  virtual nsSplittableType GetSplittableType() const = 0;

  /**
   * Continuation member functions
   */
  virtual nsIFrame* GetPrevContinuation() const = 0;
  virtual void SetPrevContinuation(nsIFrame*) = 0;
  virtual nsIFrame* GetNextContinuation() const = 0;
  virtual void SetNextContinuation(nsIFrame*) = 0;
  virtual nsIFrame* FirstContinuation() const {
    return const_cast<nsIFrame*>(this);
  }
  virtual nsIFrame* LastContinuation() const {
    return const_cast<nsIFrame*>(this);
  }

  /**
   * GetTailContinuation gets the last non-overflow-container continuation
   * in the continuation chain, i.e. where the next sibling element
   * should attach).
   */
  nsIFrame* GetTailContinuation();

  /**
   * Flow member functions
   */
  virtual nsIFrame* GetPrevInFlowVirtual() const = 0;
  nsIFrame* GetPrevInFlow() const { return GetPrevInFlowVirtual(); }
  virtual void SetPrevInFlow(nsIFrame*) = 0;

  virtual nsIFrame* GetNextInFlowVirtual() const = 0;
  nsIFrame* GetNextInFlow() const { return GetNextInFlowVirtual(); }
  virtual void SetNextInFlow(nsIFrame*) = 0;

  /**
   * Return the first frame in our current flow. 
   */
  virtual nsIFrame* FirstInFlow() const {
    return const_cast<nsIFrame*>(this);
  }

  /**
   * Return the last frame in our current flow.
   */
  virtual nsIFrame* LastInFlow() const {
    return const_cast<nsIFrame*>(this);
  }

  /**
   * Note: "width" in the names and comments on the following methods
   * means inline-size, which could be height in vertical layout
   */

  /**
   * Mark any stored intrinsic width information as dirty (requiring
   * re-calculation).  Note that this should generally not be called
   * directly; nsPresShell::FrameNeedsReflow will call it instead.
   */
  virtual void MarkIntrinsicISizesDirty() = 0;

  /**
   * Get the min-content intrinsic inline size of the frame.  This must be
   * less than or equal to the max-content intrinsic inline size.
   *
   * This is *not* affected by the CSS 'min-width', 'width', and
   * 'max-width' properties on this frame, but it is affected by the
   * values of those properties on this frame's descendants.  (It may be
   * called during computation of the values of those properties, so it
   * cannot depend on any values in the nsStylePosition for this frame.)
   *
   * The value returned should **NOT** include the space required for
   * padding and border.
   *
   * Note that many frames will cache the result of this function call
   * unless MarkIntrinsicISizesDirty is called.
   *
   * It is not acceptable for a frame to mark itself dirty when this
   * method is called.
   *
   * This method must not return a negative value.
   */
  virtual nscoord GetMinISize(nsRenderingContext *aRenderingContext) = 0;

  /**
   * Get the max-content intrinsic inline size of the frame.  This must be
   * greater than or equal to the min-content intrinsic inline size.
   *
   * Otherwise, all the comments for |GetMinISize| above apply.
   */
  virtual nscoord GetPrefISize(nsRenderingContext *aRenderingContext) = 0;

  /**
   * |InlineIntrinsicISize| represents the intrinsic width information
   * in inline layout.  Code that determines the intrinsic width of a
   * region of inline layout accumulates the result into this structure.
   * This pattern is needed because we need to maintain state
   * information about whitespace (for both collapsing and trimming).
   */
  struct InlineIntrinsicISizeData {
    InlineIntrinsicISizeData()
      : mLine(nullptr)
      , mLineContainer(nullptr)
      , mPrevLines(0)
      , mCurrentLine(0)
      , mTrailingWhitespace(0)
      , mSkipWhitespace(true)
    {}

    // The line. This may be null if the inlines are not associated with
    // a block or if we just don't know the line.
    const nsLineList_iterator* mLine;

    // The line container. Private, to ensure we always use SetLineContainer
    // to update it (so that we have a chance to store the mLineContainerWM).
    //
    // Note that nsContainerFrame::DoInlineIntrinsicISize will clear the
    // |mLine| and |mLineContainer| fields when following a next-in-flow link,
    // so we must not assume these can always be dereferenced.
  private:
    nsIFrame* mLineContainer;

    // Setter and getter for the lineContainer field:
  public:
    void SetLineContainer(nsIFrame* aLineContainer)
    {
      mLineContainer = aLineContainer;
      if (mLineContainer) {
        mLineContainerWM = mLineContainer->GetWritingMode();
      }
    }
    nsIFrame* LineContainer() const { return mLineContainer; }

    // The maximum intrinsic width for all previous lines.
    nscoord mPrevLines;

    // The maximum intrinsic width for the current line.  At a line
    // break (mandatory for preferred width; allowed for minimum width),
    // the caller should call |Break()|.
    nscoord mCurrentLine;

    // This contains the width of the trimmable whitespace at the end of
    // |mCurrentLine|; it is zero if there is no such whitespace.
    nscoord mTrailingWhitespace;

    // True if initial collapsable whitespace should be skipped.  This
    // should be true at the beginning of a block, after hard breaks
    // and when the last text ended with whitespace.
    bool mSkipWhitespace;

    // Writing mode of the line container (stored here so that we don't
    // lose track of it if the mLineContainer field is reset).
    mozilla::WritingMode mLineContainerWM;

    // Floats encountered in the lines.
    class FloatInfo {
    public:
      FloatInfo(const nsIFrame* aFrame, nscoord aWidth)
        : mFrame(aFrame), mWidth(aWidth)
      { }
      const nsIFrame* Frame() const { return mFrame; }
      nscoord         Width() const { return mWidth; }

    private:
      const nsIFrame* mFrame;
      nscoord         mWidth;
    };

    nsTArray<FloatInfo> mFloats;
  };

  struct InlineMinISizeData : public InlineIntrinsicISizeData {
    InlineMinISizeData()
      : mAtStartOfLine(true)
    {}

    // The default implementation for nsIFrame::AddInlineMinISize.
    void DefaultAddInlineMinISize(nsIFrame* aFrame,
                                  nscoord   aISize,
                                  bool      aAllowBreak = true);

    // We need to distinguish forced and optional breaks for cases where the
    // current line total is negative.  When it is, we need to ignore
    // optional breaks to prevent min-width from ending up bigger than
    // pref-width.
    void ForceBreak();

    // If the break here is actually taken, aHyphenWidth must be added to the
    // width of the current line.
    void OptionallyBreak(nscoord aHyphenWidth = 0);

    // Whether we're currently at the start of the line.  If we are, we
    // can't break (for example, between the text-indent and the first
    // word).
    bool mAtStartOfLine;
  };

  struct InlinePrefISizeData : public InlineIntrinsicISizeData {
    void ForceBreak();

    // The default implementation for nsIFrame::AddInlinePrefISize.
    void DefaultAddInlinePrefISize(nscoord aISize);
  };

  /**
   * Add the intrinsic minimum width of a frame in a way suitable for
   * use in inline layout to an |InlineIntrinsicISizeData| object that
   * represents the intrinsic width information of all the previous
   * frames in the inline layout region.
   *
   * All *allowed* breakpoints within the frame determine what counts as
   * a line for the |InlineIntrinsicISizeData|.  This means that
   * |aData->mTrailingWhitespace| will always be zero (unlike for
   * AddInlinePrefISize).
   *
   * All the comments for |GetMinISize| apply, except that this function
   * is responsible for adding padding, border, and margin and for
   * considering the effects of 'width', 'min-width', and 'max-width'.
   *
   * This may be called on any frame.  Frames that do not participate in
   * line breaking can inherit the default implementation on nsFrame,
   * which calls |GetMinISize|.
   */
  virtual void
  AddInlineMinISize(nsRenderingContext *aRenderingContext,
                    InlineMinISizeData *aData) = 0;

  /**
   * Add the intrinsic preferred width of a frame in a way suitable for
   * use in inline layout to an |InlineIntrinsicISizeData| object that
   * represents the intrinsic width information of all the previous
   * frames in the inline layout region.
   *
   * All the comments for |AddInlineMinISize| and |GetPrefISize| apply,
   * except that this fills in an |InlineIntrinsicISizeData| structure
   * based on using all *mandatory* breakpoints within the frame.
   */
  virtual void
  AddInlinePrefISize(nsRenderingContext *aRenderingContext,
                     InlinePrefISizeData *aData) = 0;

  /**
   * Return the horizontal components of padding, border, and margin
   * that contribute to the intrinsic width that applies to the parent.
   * @param aPercentageBasis the percentage basis to use for padding/margin -
   *   i.e. the Containing Block's inline-size
   */
  struct IntrinsicISizeOffsetData {
    nscoord hPadding, hBorder, hMargin;

    IntrinsicISizeOffsetData()
      : hPadding(0), hBorder(0), hMargin(0)
    {}
  };
  virtual IntrinsicISizeOffsetData
  IntrinsicISizeOffsets(nscoord aPercentageBasis = NS_UNCONSTRAINEDSIZE) = 0;

  /**
   * Return the bsize components of padding, border, and margin
   * that contribute to the intrinsic width that applies to the parent.
   * @param aPercentageBasis the percentage basis to use for padding/margin -
   *   i.e. the Containing Block's inline-size
   */
  IntrinsicISizeOffsetData
  IntrinsicBSizeOffsets(nscoord aPercentageBasis = NS_UNCONSTRAINEDSIZE);

  virtual mozilla::IntrinsicSize GetIntrinsicSize() = 0;

  /**
   * Get the intrinsic ratio of this element, or nsSize(0,0) if it has
   * no intrinsic ratio.  The intrinsic ratio is the ratio of the
   * height/width of a box with an intrinsic size or the intrinsic
   * aspect ratio of a scalable vector image without an intrinsic size.
   *
   * Either one of the sides may be zero, indicating a zero or infinite
   * ratio.
   */
  virtual nsSize GetIntrinsicRatio() = 0;

  /**
   * Bit-flags to pass to ComputeSize in |aFlags| parameter.
   */
  enum ComputeSizeFlags {
    eDefault =           0,
    /**
     * Set if the frame is in a context where non-replaced blocks should
     * shrink-wrap (e.g., it's floating, absolutely positioned, or
     * inline-block).
     */
    eShrinkWrap =        1 << 0,
    /**
     * Set if we'd like to compute our 'auto' bsize, regardless of our actual
     * corresponding computed value. (e.g. to get an intrinsic height for flex
     * items with "min-height: auto" to use during flexbox layout.)
     */
    eUseAutoBSize =      1 << 1,
    /**
     * Indicates that we should clamp the margin-box min-size to the given CB
     * size.  This is used for implementing the grid area clamping here:
     * https://drafts.csswg.org/css-grid/#min-size-auto
     */
    eIClampMarginBoxMinSize = 1 << 2, // clamp in our inline axis
    eBClampMarginBoxMinSize = 1 << 3, // clamp in our block axis
    /**
     * The frame is stretching (per CSS Box Alignment) and doesn't have an
     * Automatic Minimum Size in the indicated axis.
     * (may be used for both flex/grid items, but currently only used for Grid)
     * https://drafts.csswg.org/css-grid/#min-size-auto
     * https://drafts.csswg.org/css-align-3/#valdef-justify-self-stretch
     */
    eIApplyAutoMinSize = 1 << 4, // only has an effect when eShrinkWrap is false
  };

  /**
   * Compute the size that a frame will occupy.  Called while
   * constructing the ReflowInput to be used to Reflow the frame,
   * in order to fill its mComputedWidth and mComputedHeight member
   * variables.
   *
   * The |height| member of the return value may be
   * NS_UNCONSTRAINEDSIZE, but the |width| member must not be.
   *
   * Note that the reason that border and padding need to be passed
   * separately is so that the 'box-sizing' property can be handled.
   * Thus aMargin includes absolute positioning offsets as well.
   *
   * @param aWritingMode  The writing mode to use for the returned size
   *                      (need not match this frame's writing mode).
   *                      This is also the writing mode of the passed-in
   *                      LogicalSize parameters.
   * @param aCBSize  The size of the element's containing block.  (Well,
   *                 the |height| component isn't really.)
   * @param aAvailableWidth  The available width for 'auto' widths.
   *                         This is usually the same as aCBSize.width,
   *                         but differs in cases such as block
   *                         formatting context roots next to floats, or
   *                         in some cases of float reflow in quirks
   *                         mode.
   * @param aMargin  The sum of the vertical / horizontal margins
   *                 ***AND*** absolute positioning offsets (top, right,
   *                 bottom, left) of the frame, including actual values
   *                 resulting from percentages and from the
   *                 "hypothetical box" for absolute positioning, but
   *                 not including actual values resulting from 'auto'
   *                 margins or ignored 'auto' values in absolute
   *                 positioning.
   * @param aBorder  The sum of the vertical / horizontal border widths
   *                 of the frame.
   * @param aPadding The sum of the vertical / horizontal margins of
   *                 the frame, including actual values resulting from
   *                 percentages.
   * @param aFlags   Flags to further customize behavior (definitions above).
   */
  virtual mozilla::LogicalSize
  ComputeSize(nsRenderingContext *aRenderingContext,
              mozilla::WritingMode aWritingMode,
              const mozilla::LogicalSize& aCBSize,
              nscoord aAvailableISize,
              const mozilla::LogicalSize& aMargin,
              const mozilla::LogicalSize& aBorder,
              const mozilla::LogicalSize& aPadding,
              ComputeSizeFlags aFlags) = 0;

  /**
   * Compute a tight bounding rectangle for the frame. This is a rectangle
   * that encloses the pixels that are actually drawn. We're allowed to be
   * conservative and currently we don't try very hard. The rectangle is
   * in appunits and relative to the origin of this frame.
   *
   * This probably only needs to include frame bounds, glyph bounds, and
   * text decorations, but today it sometimes includes other things that
   * contribute to visual overflow.
   *
   * @param aDrawTarget a draw target that can be used if we need
   * to do measurement
   */
  virtual nsRect ComputeTightBounds(DrawTarget* aDrawTarget) const;

  /**
   * This function is similar to GetPrefISize and ComputeTightBounds: it
   * computes the left and right coordinates of a preferred tight bounding
   * rectangle for the frame. This is a rectangle that would enclose the pixels
   * that are drawn if we lay out the element without taking any optional line
   * breaks. The rectangle is in appunits and relative to the origin of this
   * frame. Currently, this function is only implemented for nsBlockFrame and
   * nsTextFrame and is used to determine intrinsic widths of MathML token
   * elements.

   * @param aContext a rendering context that can be used if we need
   * to do measurement
   * @param aX      computed left coordinate of the tight bounding rectangle
   * @param aXMost  computed intrinsic width of the tight bounding rectangle
   *
   */
  virtual nsresult GetPrefWidthTightBounds(nsRenderingContext* aContext,
                                           nscoord* aX,
                                           nscoord* aXMost);

  /**
   * The frame is given an available size and asked for its desired
   * size.  This is the frame's opportunity to reflow its children.
   *
   * If the frame has the NS_FRAME_IS_DIRTY bit set then it is
   * responsible for completely reflowing itself and all of its
   * descendants.
   *
   * Otherwise, if the frame has the NS_FRAME_HAS_DIRTY_CHILDREN bit
   * set, then it is responsible for reflowing at least those
   * children that have NS_FRAME_HAS_DIRTY_CHILDREN or NS_FRAME_IS_DIRTY
   * set.
   *
   * If a difference in available size from the previous reflow causes
   * the frame's size to change, it should reflow descendants as needed.
   *
   * @param aReflowOutput <i>out</i> parameter where you should return the
   *          desired size and ascent/descent info. You should include any
   *          space you want for border/padding in the desired size you return.
   *
   *          It's okay to return a desired size that exceeds the avail
   *          size if that's the smallest you can be, i.e. it's your
   *          minimum size.
   *
   *          For an incremental reflow you are responsible for invalidating
   *          any area within your frame that needs repainting (including
   *          borders). If your new desired size is different than your current
   *          size, then your parent frame is responsible for making sure that
   *          the difference between the two rects is repainted
   *
   * @param aReflowInput information about your reflow including the reason
   *          for the reflow and the available space in which to lay out. Each
   *          dimension of the available space can either be constrained or
   *          unconstrained (a value of NS_UNCONSTRAINEDSIZE).
   *
   *          Note that the available space can be negative. In this case you
   *          still must return an accurate desired size. If you're a container
   *          you must <b>always</b> reflow at least one frame regardless of the
   *          available space
   *
   * @param aStatus a return value indicating whether the frame is complete
   *          and whether the next-in-flow is dirty and needs to be reflowed
   */
  virtual void Reflow(nsPresContext*           aPresContext,
                      ReflowOutput&     aReflowOutput,
                      const ReflowInput& aReflowInput,
                      nsReflowStatus&          aStatus) = 0;

  /**
   * Post-reflow hook. After a frame is reflowed this method will be called
   * informing the frame that this reflow process is complete, and telling the
   * frame the status returned by the Reflow member function.
   *
   * This call may be invoked many times, while NS_FRAME_IN_REFLOW is set, before
   * it is finally called once with a NS_FRAME_REFLOW_COMPLETE value. When called
   * with a NS_FRAME_REFLOW_COMPLETE value the NS_FRAME_IN_REFLOW bit in the
   * frame state will be cleared.
   *
   * XXX This doesn't make sense. If the frame is reflowed but not complete, then
   * the status should be NS_FRAME_NOT_COMPLETE and not NS_FRAME_COMPLETE
   * XXX Don't we want the semantics to dictate that we only call this once for
   * a given reflow?
   */
  virtual void DidReflow(nsPresContext*           aPresContext,
                         const ReflowInput* aReflowInput,
                         nsDidReflowStatus        aStatus) = 0;

  /**
   * Updates the overflow areas of the frame. This can be called if an
   * overflow area of the frame's children has changed without reflowing.
   * @return true if either of the overflow areas for this frame have changed.
   */
  bool UpdateOverflow();

  /**
   * Computes any overflow area created by the frame itself (outside of the
   * frame bounds) and includes it into aOverflowAreas.
   *
   * Returns false if updating overflow isn't supported for this frame.
   * If the frame requires a reflow instead, then it is responsible
   * for scheduling one.
   */
  virtual bool ComputeCustomOverflow(nsOverflowAreas& aOverflowAreas) = 0;

  /**
   * Computes any overflow area created by children of this frame and
   * includes it into aOverflowAreas.
   */
  virtual void UnionChildOverflow(nsOverflowAreas& aOverflowAreas) = 0;

  /**
   * Helper method used by block reflow to identify runs of text so
   * that proper word-breaking can be done.
   *
   * @return 
   *    true if we can continue a "text run" through the frame. A
   *    text run is text that should be treated contiguously for line
   *    and word breaking.
   */
  virtual bool CanContinueTextRun() const = 0;

  /**
   * Computes an approximation of the rendered text of the frame and its
   * continuations. Returns nothing for non-text frames.
   * The appended text will often not contain all the whitespace from source,
   * depending on CSS white-space processing.
   * if aEndOffset goes past end, use the text up to the string's end.
   * Call this on the primary frame for a text node.
   * aStartOffset and aEndOffset can be content offsets or offsets in the
   * rendered text, depending on aOffsetType.
   * Returns a string, as well as offsets identifying the start of the text
   * within the rendered text for the whole node, and within the text content
   * of the node.
   */
  struct RenderedText {
    nsAutoString mString;
    uint32_t mOffsetWithinNodeRenderedText;
    int32_t mOffsetWithinNodeText;
    RenderedText() : mOffsetWithinNodeRenderedText(0),
        mOffsetWithinNodeText(0) {}
  };
  enum class TextOffsetType {
    // Passed-in start and end offsets are within the content text.
    OFFSETS_IN_CONTENT_TEXT,
    // Passed-in start and end offsets are within the rendered text.
    OFFSETS_IN_RENDERED_TEXT
  };
  enum class TrailingWhitespace {
    TRIM_TRAILING_WHITESPACE,
    // Spaces preceding a caret at the end of a line should not be trimmed
    DONT_TRIM_TRAILING_WHITESPACE
  };
  virtual RenderedText GetRenderedText(uint32_t aStartOffset = 0,
                                       uint32_t aEndOffset = UINT32_MAX,
                                       TextOffsetType aOffsetType =
                                           TextOffsetType::OFFSETS_IN_CONTENT_TEXT,
                                       TrailingWhitespace aTrimTrailingWhitespace =
                                           TrailingWhitespace::TRIM_TRAILING_WHITESPACE)
  { return RenderedText(); }

  /**
   * Returns true if the frame contains any non-collapsed characters.
   * This method is only available for text frames, and it will return false
   * for all other frame types.
   */
  virtual bool HasAnyNoncollapsedCharacters()
  { return false; }

  /**
   * Accessor functions to get/set the associated view object
   *
   * GetView returns non-null if and only if |HasView| returns true.
   */
  bool HasView() const { return !!(mState & NS_FRAME_HAS_VIEW); }
  nsView* GetView() const;
  nsresult SetView(nsView* aView);

  /**
   * Find the closest view (on |this| or an ancestor).
   * If aOffset is non-null, it will be set to the offset of |this|
   * from the returned view.
   */
  nsView* GetClosestView(nsPoint* aOffset = nullptr) const;

  /**
   * Find the closest ancestor (excluding |this| !) that has a view
   */
  nsIFrame* GetAncestorWithView() const;

  /**
   * Get the offset between the coordinate systems of |this| and aOther.
   * Adding the return value to a point in the coordinate system of |this|
   * will transform the point to the coordinate system of aOther.
   *
   * aOther must be non-null.
   * 
   * This function is fastest when aOther is an ancestor of |this|.
   *
   * This function _DOES NOT_ work across document boundaries.
   * Use this function only when |this| and aOther are in the same document.
   *
   * NOTE: this actually returns the offset from aOther to |this|, but
   * that offset is added to transform _coordinates_ from |this| to
   * aOther.
   */
  nsPoint GetOffsetTo(const nsIFrame* aOther) const;

  /**
   * Get the offset between the coordinate systems of |this| and aOther
   * expressed in appunits per dev pixel of |this|' document. Adding the return
   * value to a point that is relative to the origin of |this| will make the
   * point relative to the origin of aOther but in the appunits per dev pixel
   * ratio of |this|.
   *
   * aOther must be non-null.
   * 
   * This function is fastest when aOther is an ancestor of |this|.
   *
   * This function works across document boundaries.
   *
   * Because this function may cross document boundaries that have different
   * app units per dev pixel ratios it needs to be used very carefully.
   *
   * NOTE: this actually returns the offset from aOther to |this|, but
   * that offset is added to transform _coordinates_ from |this| to
   * aOther.
   */
  nsPoint GetOffsetToCrossDoc(const nsIFrame* aOther) const;

  /**
   * Like GetOffsetToCrossDoc, but the caller can specify which appunits
   * to return the result in.
   */
  nsPoint GetOffsetToCrossDoc(const nsIFrame* aOther, const int32_t aAPD) const;

  /**
   * Get the screen rect of the frame in pixels.
   * @return the pixel rect of the frame in screen coordinates.
   */
  nsIntRect GetScreenRect() const;

  /**
   * Get the screen rect of the frame in app units.
   * @return the app unit rect of the frame in screen coordinates.
   */
  nsRect GetScreenRectInAppUnits() const;

  /**
   * Returns the offset from this frame to the closest geometric parent that
   * has a view. Also returns the containing view or null in case of error
   */
  void GetOffsetFromView(nsPoint& aOffset, nsView** aView) const;

  /**
   * Returns the nearest widget containing this frame. If this frame has a
   * view and the view has a widget, then this frame's widget is
   * returned, otherwise this frame's geometric parent is checked
   * recursively upwards.
   */
  nsIWidget* GetNearestWidget() const;

  /**
   * Same as GetNearestWidget() above but uses an outparam to return the offset
   * of this frame to the returned widget expressed in appunits of |this| (the
   * widget might be in a different document with a different zoom).
   */
  nsIWidget* GetNearestWidget(nsPoint& aOffset) const;

  /**
   * Whether the content for this frame is disabled, used for event handling.
   */
  bool IsContentDisabled() const;

  /**
   * Get the "type" of the frame. May return nullptr.
   *
   * @see nsGkAtoms
   */
  virtual nsIAtom* GetType() const = 0;

  /**
   * Returns a transformation matrix that converts points in this frame's
   * coordinate space to points in some ancestor frame's coordinate space.
   * The frame decides which ancestor it will use as a reference point.
   * If this frame has no ancestor, aOutAncestor will be set to null.
   *
   * @param aStopAtAncestor don't look further than aStopAtAncestor. If null,
   *   all ancestors (including across documents) will be traversed.
   * @param aOutAncestor [out] The ancestor frame the frame has chosen.  If
   *   this frame has no ancestor, *aOutAncestor will be set to null. If
   * this frame is not a root frame, then *aOutAncestor will be in the same
   * document as this frame. If this frame IsTransformed(), then *aOutAncestor
   * will be the parent frame (if not preserve-3d) or the nearest non-transformed
   * ancestor (if preserve-3d).
   * @return A Matrix4x4 that converts points in this frame's coordinate space
   *   into points in aOutAncestor's coordinate space.
   */
  Matrix4x4 GetTransformMatrix(const nsIFrame* aStopAtAncestor,
                               nsIFrame **aOutAncestor);

  /**
   * Bit-flags to pass to IsFrameOfType()
   */
  enum {
    eMathML =                           1 << 0,
    eSVG =                              1 << 1,
    eSVGForeignObject =                 1 << 2,
    eSVGContainer =                     1 << 3,
    eSVGGeometry =                      1 << 4,
    eSVGPaintServer =                   1 << 5,
    eBidiInlineContainer =              1 << 6,
    // the frame is for a replaced element, such as an image
    eReplaced =                         1 << 7,
    // Frame that contains a block but looks like a replaced element
    // from the outside
    eReplacedContainsBlock =            1 << 8,
    // A frame that participates in inline reflow, i.e., one that
    // requires ReflowInput::mLineLayout.
    eLineParticipant =                  1 << 9,
    eXULBox =                           1 << 10,
    eCanContainOverflowContainers =     1 << 11,
    eBlockFrame =                       1 << 12,
    eTablePart =                        1 << 13,
    // If this bit is set, the frame doesn't allow ignorable whitespace as
    // children. For example, the whitespace between <table>\n<tr>\n<td>
    // will be excluded during the construction of children. 
    eExcludesIgnorableWhitespace =      1 << 14,
    eSupportsCSSTransforms =            1 << 15,

    // A replaced element that has replaced-element sizing
    // characteristics (i.e., like images or iframes), as opposed to
    // inline-block sizing characteristics (like form controls).
    eReplacedSizing =                   1 << 16,

    // These are to allow nsFrame::Init to assert that IsFrameOfType
    // implementations all call the base class method.  They are only
    // meaningful in DEBUG builds.
    eDEBUGAllFrames =                   1 << 30,
    eDEBUGNoFrames =                    1 << 31
  };

  /**
   * API for doing a quick check if a frame is of a given
   * type. Returns true if the frame matches ALL flags passed in.
   *
   * Implementations should always override with inline virtual
   * functions that call the base class's IsFrameOfType method.
   */
  virtual bool IsFrameOfType(uint32_t aFlags) const
  {
#ifdef DEBUG
    return !(aFlags & ~(nsIFrame::eDEBUGAllFrames | nsIFrame::eSupportsCSSTransforms));
#else
    return !(aFlags & ~nsIFrame::eSupportsCSSTransforms);
#endif
  }

  /**
   * Returns true if the frame is a block wrapper.
   */
  bool IsBlockWrapper() const;

  /**
   * Get this frame's CSS containing block.
   *
   * The algorithm is defined in
   * http://www.w3.org/TR/CSS2/visudet.html#containing-block-details.
   *
   * NOTE: This is guaranteed to return a non-null pointer when invoked on any
   * frame other than the root frame.
   *
   * Requires SKIP_SCROLLED_FRAME to get behaviour matching the spec, otherwise
   * it can return anonymous inner scrolled frames. Bug 1204044 is filed for
   * investigating whether any of the callers actually require the default
   * behaviour.
   */
  enum {
    // If the containing block is an anonymous scrolled frame, then skip over
    // this and return the outer scroll frame.
    SKIP_SCROLLED_FRAME = 0x01
  };
  nsIFrame* GetContainingBlock(uint32_t aFlags = 0) const;

  /**
   * Is this frame a containing block for floating elements?
   * Note that very few frames are, so default to false.
   */
  virtual bool IsFloatContainingBlock() const { return false; }

  /**
   * Is this a leaf frame?  Frames that want the frame constructor to be able
   * to construct kids for them should return false, all others should return
   * true.  Note that returning true here does not mean that the frame _can't_
   * have kids.  It could still have kids created via
   * nsIAnonymousContentCreator.  Returning true indicates that "normal"
   * (non-anonymous, XBL-bound, CSS generated content, etc) children should not
   * be constructed.
   */
  virtual bool IsLeaf() const;

  /**
   * Marks all display items created by this frame as needing a repaint,
   * and calls SchedulePaint() if requested and one is not already pending.
   *
   * This includes all display items created by this frame, including
   * container types.
   *
   * @param aDisplayItemKey If specified, only issues an invalidate
   * if this frame painted a display item of that type during the 
   * previous paint. SVG rendering observers are always notified.
   */
  virtual void InvalidateFrame(uint32_t aDisplayItemKey = 0);

  /**
   * Same as InvalidateFrame(), but only mark a fixed rect as needing
   * repainting.
   *
   * @param aRect The rect to invalidate, relative to the TopLeft of the
   * frame's border box.
   * @param aDisplayItemKey If specified, only issues an invalidate
   * if this frame painted a display item of that type during the 
   * previous paint. SVG rendering observers are always notified.
   */
  virtual void InvalidateFrameWithRect(const nsRect& aRect, uint32_t aDisplayItemKey = 0);
  
  /**
   * Calls InvalidateFrame() on all frames descendant frames (including
   * this one).
   * 
   * This function doesn't walk through placeholder frames to invalidate
   * the out-of-flow frames.
   *
   * @param aDisplayItemKey If specified, only issues an invalidate
   * if this frame painted a display item of that type during the 
   * previous paint. SVG rendering observers are always notified.
   */
  void InvalidateFrameSubtree(uint32_t aDisplayItemKey = 0);

  /**
   * Called when a frame is about to be removed and needs to be invalidated.
   * Normally does nothing since DLBI handles removed frames.
   */
  virtual void InvalidateFrameForRemoval() {}

  /**
   * When HasUserData(frame->LayerIsPrerenderedDataKey()), then the
   * entire overflow area of this frame has been rendered in its
   * layer(s).
   */
  static void* LayerIsPrerenderedDataKey() { 
    return &sLayerIsPrerenderedDataKey;
  }
  static uint8_t sLayerIsPrerenderedDataKey;

   /**
   * Try to update this frame's transform without invalidating any
   * content.  Return true iff successful.  If unsuccessful, the
   * caller is responsible for scheduling an invalidating paint.
   *
   * If the result is true, aLayerResult will be filled in with the
   * transform layer for the frame.
   */
  bool TryUpdateTransformOnly(Layer** aLayerResult);

  /**
   * Checks if a frame has had InvalidateFrame() called on it since the
   * last paint.
   *
   * If true, then the invalid rect is returned in aRect, with an
   * empty rect meaning all pixels drawn by this frame should be
   * invalidated.
   * If false, aRect is left unchanged.
   */
  bool IsInvalid(nsRect& aRect);
 
  /**
   * Check if any frame within the frame subtree (including this frame) 
   * returns true for IsInvalid().
   */
  bool HasInvalidFrameInSubtree()
  {
    return HasAnyStateBits(NS_FRAME_NEEDS_PAINT | NS_FRAME_DESCENDANT_NEEDS_PAINT);
  }

  /**
   * Removes the invalid state from the current frame and all
   * descendant frames.
   */
  void ClearInvalidationStateBits();

  /**
   * Ensures that the refresh driver is running, and schedules a view 
   * manager flush on the next tick.
   *
   * The view manager flush will update the layer tree, repaint any 
   * invalid areas in the layer tree and schedule a layer tree
   * composite operation to display the layer tree.
   *
   * In general it is not necessary for frames to call this when they change.
   * For example, changes that result in a reflow will have this called for
   * them by PresContext::DoReflow when the reflow begins. Style changes that 
   * do not trigger a reflow should have this called for them by
   * DoApplyRenderingChangeToTree.
   *
   * @param aType PAINT_COMPOSITE_ONLY : No changes have been made
   * that require a layer tree update, so only schedule a layer
   * tree composite.
   * PAINT_DELAYED_COMPRESS : Schedule a paint to be executed after a delay, and
   * put FrameLayerBuilder in 'compressed' mode that avoids short cut optimizations.
   */
  enum PaintType {
    PAINT_DEFAULT = 0,
    PAINT_COMPOSITE_ONLY,
    PAINT_DELAYED_COMPRESS
  };
  void SchedulePaint(PaintType aType = PAINT_DEFAULT);

  /**
   * Checks if the layer tree includes a dedicated layer for this 
   * frame/display item key pair, and invalidates at least aDamageRect
   * area within that layer.
   *
   * If no layer is found, calls InvalidateFrame() instead.
   *
   * @param aDamageRect Area of the layer to invalidate.
   * @param aFrameDamageRect If no layer is found, the area of the frame to
   *                         invalidate. If null, the entire frame will be
   *                         invalidated.
   * @param aDisplayItemKey Display item type.
   * @param aFlags UPDATE_IS_ASYNC : Will skip the invalidation
   * if the found layer is being composited by a remote
   * compositor.
   * @return Layer, if found, nullptr otherwise.
   */
  enum {
    UPDATE_IS_ASYNC = 1 << 0
  };
  Layer* InvalidateLayer(uint32_t aDisplayItemKey,
                         const nsIntRect* aDamageRect = nullptr,
                         const nsRect* aFrameDamageRect = nullptr,
                         uint32_t aFlags = 0);

  /**
   * Returns a rect that encompasses everything that might be painted by
   * this frame.  This includes this frame, all its descendant frames, this
   * frame's outline, and descendant frames' outline, but does not include
   * areas clipped out by the CSS "overflow" and "clip" properties.
   *
   * HasOverflowRects() (below) will return true when this overflow
   * rect has been explicitly set, even if it matches mRect.
   * XXX Note: because of a space optimization using the formula above,
   * during reflow this function does not give accurate data if
   * FinishAndStoreOverflow has been called but mRect hasn't yet been
   * updated yet.  FIXME: This actually isn't true, but it should be.
   *
   * The visual overflow rect should NEVER be used for things that
   * affect layout.  The scrollable overflow rect is permitted to affect
   * layout.
   *
   * @return the rect relative to this frame's origin, but after
   * CSS transforms have been applied (i.e. not really this frame's coordinate
   * system, and may not contain the frame's border-box, e.g. if there
   * is a CSS transform scaling it down)
   */
  nsRect GetVisualOverflowRect() const {
    return GetOverflowRect(eVisualOverflow);
  }

  /**
   * Returns a rect that encompasses the area of this frame that the
   * user should be able to scroll to reach.  This is similar to
   * GetVisualOverflowRect, but does not include outline or shadows, and
   * may in the future include more margins than visual overflow does.
   * It does not include areas clipped out by the CSS "overflow" and
   * "clip" properties.
   *
   * HasOverflowRects() (below) will return true when this overflow
   * rect has been explicitly set, even if it matches mRect.
   * XXX Note: because of a space optimization using the formula above,
   * during reflow this function does not give accurate data if
   * FinishAndStoreOverflow has been called but mRect hasn't yet been
   * updated yet.
   *
   * @return the rect relative to this frame's origin, but after
   * CSS transforms have been applied (i.e. not really this frame's coordinate
   * system, and may not contain the frame's border-box, e.g. if there
   * is a CSS transform scaling it down)
   */
  nsRect GetScrollableOverflowRect() const {
    return GetOverflowRect(eScrollableOverflow);
  }

  nsRect GetOverflowRect(nsOverflowType aType) const;

  nsOverflowAreas GetOverflowAreas() const;

  /**
   * Same as GetOverflowAreas, except in this frame's coordinate
   * system (before transforms are applied).
   *
   * @return the overflow areas relative to this frame, before any CSS transforms have
   * been applied, i.e. in this frame's coordinate system
   */
  nsOverflowAreas GetOverflowAreasRelativeToSelf() const;

  /**
   * Same as GetScrollableOverflowRect, except relative to the parent
   * frame.
   *
   * @return the rect relative to the parent frame, in the parent frame's
   * coordinate system
   */
  nsRect GetScrollableOverflowRectRelativeToParent() const;

  /**
   * Same as GetScrollableOverflowRect, except in this frame's coordinate
   * system (before transforms are applied).
   *
   * @return the rect relative to this frame, before any CSS transforms have
   * been applied, i.e. in this frame's coordinate system
   */
  nsRect GetScrollableOverflowRectRelativeToSelf() const;

  /**
   * Like GetVisualOverflowRect, except in this frame's
   * coordinate system (before transforms are applied).
   *
   * @return the rect relative to this frame, before any CSS transforms have
   * been applied, i.e. in this frame's coordinate system
   */
  nsRect GetVisualOverflowRectRelativeToSelf() const;

  /**
   * Same as GetVisualOverflowRect, except relative to the parent
   * frame.
   *
   * @return the rect relative to the parent frame, in the parent frame's
   * coordinate system
   */
  nsRect GetVisualOverflowRectRelativeToParent() const;

  /**
   * Returns this frame's visual overflow rect as it would be before taking
   * account of SVG effects or transforms. The rect returned is relative to
   * this frame.
   */
  nsRect GetPreEffectsVisualOverflowRect() const;

  /**
   * Store the overflow area in the frame's mOverflow.mVisualDeltas
   * fields or as a frame property in the frame manager so that it can
   * be retrieved later without reflowing the frame. Returns true if either of
   * the overflow areas changed.
   */
  bool FinishAndStoreOverflow(nsOverflowAreas& aOverflowAreas,
                              nsSize aNewSize, nsSize* aOldSize = nullptr);

  bool FinishAndStoreOverflow(ReflowOutput* aMetrics) {
    return FinishAndStoreOverflow(aMetrics->mOverflowAreas,
                                  nsSize(aMetrics->Width(), aMetrics->Height()));
  }

  /**
   * Returns whether the frame has an overflow rect that is different from
   * its border-box.
   */
  bool HasOverflowAreas() const {
    return mOverflow.mType != NS_FRAME_OVERFLOW_NONE;
  }

  /**
   * Removes any stored overflow rects (visual and scrollable) from the frame.
   * Returns true if the overflow changed.
   */
  bool ClearOverflowRects();

  /**
   * Determine whether borders, padding, margins etc should NOT be applied
   * on certain sides of the frame.
   * @see mozilla::Sides in gfx/2d/BaseMargin.h
   * @see mozilla::LogicalSides in layout/generic/WritingModes.h
   *
   * @note (See also bug 743402, comment 11) GetSkipSides() checks to see
   *       if this frame has a previous or next continuation to determine
   *       if a side should be skipped.
   *       Unfortunately, this only works after reflow has been completed. In
   *       lieu of this, during reflow, an ReflowInput parameter can be
   *       passed in, indicating that it should be used to determine if sides
   *       should be skipped during reflow.
   */
  Sides GetSkipSides(const ReflowInput* aReflowInput = nullptr) const;
  virtual LogicalSides
  GetLogicalSkipSides(const ReflowInput* aReflowInput = nullptr) const {
    return LogicalSides();
  }

  /**
   * @returns true if this frame is selected.
   */
  bool IsSelected() const;

  /**
   *  called to discover where this frame, or a parent frame has user-select style
   *  applied, which affects that way that it is selected.
   *    
   *  @param aIsSelectable out param. Set to true if the frame can be selected
   *                       (i.e. is not affected by user-select: none)
   *  @param aSelectStyle  out param. Returns the type of selection style found
   *                        (using values defined in nsStyleConsts.h).
   */
  virtual nsresult IsSelectable(bool* aIsSelectable,
                            mozilla::StyleUserSelect* aSelectStyle) const = 0;

  /** 
   *  Called to retrieve the SelectionController associated with the frame.
   *  @param aSelCon will contain the selection controller associated with
   *  the frame.
   */
  virtual nsresult  GetSelectionController(nsPresContext *aPresContext, nsISelectionController **aSelCon) = 0;

  /**
   *  Call to get nsFrameSelection for this frame.
   */
  already_AddRefed<nsFrameSelection> GetFrameSelection();

  /**
   * GetConstFrameSelection returns an object which methods are safe to use for
   * example in nsIFrame code.
   */
  const nsFrameSelection* GetConstFrameSelection() const;

  /**
   *  called to find the previous/next character, word, or line  returns the actual 
   *  nsIFrame and the frame offset.  THIS DOES NOT CHANGE SELECTION STATE
   *  uses frame's begin selection state to start. if no selection on this frame will 
   *  return NS_ERROR_FAILURE
   *  @param aPOS is defined in nsFrameSelection
   */
  virtual nsresult PeekOffset(nsPeekOffsetStruct *aPos);

  /**
   *  called to find the previous/next non-anonymous selectable leaf frame.
   *  @param aDirection [in] the direction to move in (eDirPrevious or eDirNext)
   *  @param aVisual [in] whether bidi caret behavior is visual (true) or logical (false)
   *  @param aJumpLines [in] whether to allow jumping across line boundaries
   *  @param aScrollViewStop [in] whether to stop when reaching a scroll frame boundary
   *  @param aOutFrame [out] the previous/next selectable leaf frame
   *  @param aOutOffset [out] 0 indicates that we arrived at the beginning of the output frame;
   *                          -1 indicates that we arrived at its end.
   *  @param aOutJumpedLine [out] whether this frame and the returned frame are on different lines
   *  @param aOutMovedOverNonSelectableText [out] whether we jumped over a non-selectable
   *                                              frame during the search
   */
  nsresult GetFrameFromDirection(nsDirection aDirection, bool aVisual,
                                 bool aJumpLines, bool aScrollViewStop,
                                 nsIFrame** aOutFrame, int32_t* aOutOffset,
                                 bool* aOutJumpedLine, bool* aOutMovedOverNonSelectableText);

  /**
   *  called to see if the children of the frame are visible from indexstart to index end.
   *  this does not change any state. returns true only if the indexes are valid and any of
   *  the children are visible.  for textframes this index is the character index.
   *  if aStart = aEnd result will be false
   *  @param aStart start index of first child from 0-N (number of children)
   *  @param aEnd   end index of last child from 0-N
   *  @param aRecurse should this frame talk to siblings to get to the contents other children?
   *  @param aFinished did this frame have the aEndIndex? or is there more work to do
   *  @param _retval  return value true or false. false = range is not rendered.
   */
  virtual nsresult CheckVisibility(nsPresContext* aContext, int32_t aStartIndex, int32_t aEndIndex, bool aRecurse, bool *aFinished, bool *_retval)=0;

  /**
   * Called to tell a frame that one of its child frames is dirty (i.e.,
   * has the NS_FRAME_IS_DIRTY *or* NS_FRAME_HAS_DIRTY_CHILDREN bit
   * set).  This should always set the NS_FRAME_HAS_DIRTY_CHILDREN on
   * the frame, and may do other work.
   */
  virtual void ChildIsDirty(nsIFrame* aChild) = 0;

  /**
   * Called to retrieve this frame's accessible.
   * If this frame implements Accessibility return a valid accessible
   * If not return NS_ERROR_NOT_IMPLEMENTED.
   * Note: Accessible must be refcountable. Do not implement directly on your frame
   * Use a mediatior of some kind.
   */
#ifdef ACCESSIBILITY
  virtual mozilla::a11y::AccType AccessibleType() = 0;
#endif

  /**
   * Get the frame whose style context should be the parent of this
   * frame's style context (i.e., provide the parent style context).
   * This frame must either be an ancestor of this frame or a child.  If
   * this returns a child frame, then the child frame must be sure to
   * return a grandparent or higher!  Furthermore, if a child frame is
   * returned it must have the same GetContent() as this frame.
   *
   * @param aProviderFrame (out) the frame associated with the returned value
   *     or nullptr if the style context is for display:contents content.
   * @return The style context that should be the parent of this frame's
   *         style context.  Null is permitted, and means that this frame's
   *         style context should be the root of the style context tree.
   */
  virtual nsStyleContext* GetParentStyleContext(nsIFrame** aProviderFrame) const = 0;

  /**
   * Determines whether a frame is visible for painting;
   * taking into account whether it is painting a selection or printing.
   */
  bool IsVisibleForPainting(nsDisplayListBuilder* aBuilder);
  /**
   * Determines whether a frame is visible for painting or collapsed;
   * taking into account whether it is painting a selection or printing,
   */
  bool IsVisibleOrCollapsedForPainting(nsDisplayListBuilder* aBuilder);
  /**
   * As above, but slower because we have to recompute some stuff that
   * aBuilder already has.
   */
  bool IsVisibleForPainting();
  /**
   * Check whether this frame is visible in the current selection. Returns
   * true if there is no current selection.
   */
  bool IsVisibleInSelection(nsDisplayListBuilder* aBuilder);

  /**
   * Overridable function to determine whether this frame should be considered
   * "in" the given non-null aSelection for visibility purposes.
   */  
  virtual bool IsVisibleInSelection(nsISelection* aSelection);

  /**
   * Determines whether this frame is a pseudo stacking context, looking
   * only as style --- i.e., assuming that it's in-flow and not a replaced
   * element and not an SVG element.
   * XXX maybe check IsTransformed()?
   */
  bool IsPseudoStackingContextFromStyle();

  virtual bool HonorPrintBackgroundSettings() { return true; }

  /**
   * Determine whether the frame is logically empty, which is roughly
   * whether the layout would be the same whether or not the frame is
   * present.  Placeholder frames should return true.  Block frames
   * should be considered empty whenever margins collapse through them,
   * even though those margins are relevant.  Text frames containing
   * only whitespace that does not contribute to the height of the line
   * should return true.
   */
  virtual bool IsEmpty() = 0;
  /**
   * Return the same as IsEmpty(). This may only be called after the frame
   * has been reflowed and before any further style or content changes.
   */
  virtual bool CachedIsEmpty();
  /**
   * Determine whether the frame is logically empty, assuming that all
   * its children are empty.
   */
  virtual bool IsSelfEmpty() = 0;

  /**
   * IsGeneratedContentFrame returns whether a frame corresponds to
   * generated content
   *
   * @return whether the frame correspods to generated content
   */
  bool IsGeneratedContentFrame() const {
    return (mState & NS_FRAME_GENERATED_CONTENT) != 0;
  }

  /**
   * IsPseudoFrame returns whether a frame is a pseudo frame (eg an
   * anonymous table-row frame created for a CSS table-cell without an
   * enclosing table-row.
   *
   * @param aParentContent the content node corresponding to the parent frame
   * @return whether the frame is a pseudo frame
   */   
  bool IsPseudoFrame(const nsIContent* aParentContent) {
    return mContent == aParentContent;
  }

/**
 * Support for reading and writing properties on the frame.
 * These call through to the frame's FrameProperties object, if it
 * exists, but avoid creating it if no property is ever set.
 */
template<typename T>
FrameProperties::PropertyType<T>
GetProperty(FrameProperties::Descriptor<T> aProperty,
            bool* aFoundResult = nullptr) const
{
  return mProperties.Get(aProperty, aFoundResult);
}

template<typename T>
bool HasProperty(FrameProperties::Descriptor<T> aProperty) const
{
    return mProperties.Has(aProperty);
}

template<typename T>
void SetProperty(FrameProperties::Descriptor<T> aProperty,
                 FrameProperties::PropertyType<T> aValue)
{
  mProperties.Set(aProperty, aValue, this);
}

template<typename T>
FrameProperties::PropertyType<T>
RemoveProperty(FrameProperties::Descriptor<T> aProperty,
               bool* aFoundResult = nullptr)
{
  return mProperties.Remove(aProperty, aFoundResult);
}

template<typename T>
void DeleteProperty(FrameProperties::Descriptor<T> aProperty)
{
  mProperties.Delete(aProperty, this);
}

void DeleteAllProperties()
{
  mProperties.DeleteAll(this);
}

// Reports size of the FrameProperties for this frame and its descendants
size_t SizeOfFramePropertiesForTree(mozilla::MallocSizeOf aMallocSizeOf) const;

  /**
   * Return true if and only if this frame obeys visibility:hidden.
   * if it does not, then nsContainerFrame will hide its view even though
   * this means children can't be made visible again.
   */
  virtual bool SupportsVisibilityHidden() { return true; }

  /**
   * Returns the clip rect set via the 'clip' property, if the 'clip' property
   * applies to this frame; otherwise returns Nothing(). The 'clip' property
   * applies to HTML frames if they are absolutely positioned. The 'clip'
   * property applies to SVG frames regardless of the value of the 'position'
   * property.
   *
   * The coordinates of the returned rectangle are relative to this frame's
   * origin.
   */
  Maybe<nsRect> GetClipPropClipRect(const nsStyleDisplay* aDisp,
                                    const nsStyleEffects* aEffects,
                                    const nsSize& aSize) const;

  /**
   * Check if this frame is focusable and in the current tab order.
   * Tabbable is indicated by a nonnegative tabindex & is a subset of focusable.
   * For example, only the selected radio button in a group is in the 
   * tab order, unless the radio group has no selection in which case
   * all of the visible, non-disabled radio buttons in the group are 
   * in the tab order. On the other hand, all of the visible, non-disabled 
   * radio buttons are always focusable via clicking or script.
   * Also, depending on the pref accessibility.tabfocus some widgets may be 
   * focusable but removed from the tab order. This is the default on
   * Mac OS X, where fewer items are focusable.
   * @param  [in, optional] aTabIndex the computed tab index
   *         < 0 if not tabbable
   *         == 0 if in normal tab order
   *         > 0 can be tabbed to in the order specified by this value
   * @param  [in, optional] aWithMouse, is this focus query for mouse clicking
   * @return whether the frame is focusable via mouse, kbd or script.
   */
  virtual bool IsFocusable(int32_t *aTabIndex = nullptr, bool aWithMouse = false);

  // BOX LAYOUT METHODS
  // These methods have been migrated from nsIBox and are in the process of
  // being refactored. DO NOT USE OUTSIDE OF XUL.
  bool IsXULBoxFrame() const
  {
    return IsFrameOfType(nsIFrame::eXULBox);
  }

  enum Halignment {
    hAlign_Left,
    hAlign_Right,
    hAlign_Center
  };

  enum Valignment {
    vAlign_Top,
    vAlign_Middle,
    vAlign_BaseLine,
    vAlign_Bottom
  };

  /**
   * This calculates the minimum size required for a box based on its state
   * @param[in] aBoxLayoutState The desired state to calculate for
   * @return The minimum size
   */
  virtual nsSize GetXULMinSize(nsBoxLayoutState& aBoxLayoutState) = 0;

  /**
   * This calculates the preferred size of a box based on its state
   * @param[in] aBoxLayoutState The desired state to calculate for
   * @return The preferred size
   */
  virtual nsSize GetXULPrefSize(nsBoxLayoutState& aBoxLayoutState) = 0;

  /**
   * This calculates the maximum size for a box based on its state
   * @param[in] aBoxLayoutState The desired state to calculate for
   * @return The maximum size
   */    
  virtual nsSize GetXULMaxSize(nsBoxLayoutState& aBoxLayoutState) = 0;

  /**
   * This returns the minimum size for the scroll area if this frame is
   * being scrolled. Usually it's (0,0).
   */
  virtual nsSize GetXULMinSizeForScrollArea(nsBoxLayoutState& aBoxLayoutState) = 0;

  // Implemented in nsBox, used in nsBoxFrame
  uint32_t GetXULOrdinal();

  virtual nscoord GetXULFlex() = 0;
  virtual nscoord GetXULBoxAscent(nsBoxLayoutState& aBoxLayoutState) = 0;
  virtual bool IsXULCollapsed() = 0;
  // This does not alter the overflow area. If the caller is changing
  // the box size, the caller is responsible for updating the overflow
  // area. It's enough to just call XULLayout or SyncLayout on the
  // box. You can pass true to aRemoveOverflowArea as a
  // convenience.
  virtual void SetXULBounds(nsBoxLayoutState& aBoxLayoutState, const nsRect& aRect,
                            bool aRemoveOverflowAreas = false) = 0;
  nsresult XULLayout(nsBoxLayoutState& aBoxLayoutState);
  // Box methods.  Note that these do NOT just get the CSS border, padding,
  // etc.  They also talk to nsITheme.
  virtual nsresult GetXULBorderAndPadding(nsMargin& aBorderAndPadding);
  virtual nsresult GetXULBorder(nsMargin& aBorder)=0;
  virtual nsresult GetXULPadding(nsMargin& aBorderAndPadding)=0;
  virtual nsresult GetXULMargin(nsMargin& aMargin)=0;
  virtual void SetXULLayoutManager(nsBoxLayout* aLayout) { }
  virtual nsBoxLayout* GetXULLayoutManager() { return nullptr; }
  nsresult GetXULClientRect(nsRect& aContentRect);

  virtual uint32_t GetXULLayoutFlags()
  { return 0; }

  // For nsSprocketLayout
  virtual Valignment GetXULVAlign() const = 0;
  virtual Halignment GetXULHAlign() const = 0;

  bool IsXULHorizontal() const { return (mState & NS_STATE_IS_HORIZONTAL) != 0; }
  bool IsXULNormalDirection() const { return (mState & NS_STATE_IS_DIRECTION_NORMAL) != 0; }

  nsresult XULRedraw(nsBoxLayoutState& aState);
  virtual nsresult XULRelayoutChildAtOrdinal(nsIFrame* aChild)=0;

#ifdef DEBUG_LAYOUT
  virtual nsresult SetXULDebug(nsBoxLayoutState& aState, bool aDebug)=0;
  virtual nsresult GetXULDebug(bool& aDebug)=0;

  virtual nsresult XULDumpBox(FILE* out)=0;
#endif

  static bool AddXULPrefSize(nsIFrame* aBox, nsSize& aSize, bool& aWidth, bool& aHeightSet);
  static bool AddXULMinSize(nsBoxLayoutState& aState, nsIFrame* aBox,
                            nsSize& aSize, bool& aWidth, bool& aHeightSet);
  static bool AddXULMaxSize(nsIFrame* aBox, nsSize& aSize, bool& aWidth, bool& aHeightSet);
  static bool AddXULFlex(nsIFrame* aBox, nscoord& aFlex);

  // END OF BOX LAYOUT METHODS
  // The above methods have been migrated from nsIBox and are in the process of
  // being refactored. DO NOT USE OUTSIDE OF XUL.

  /**
   * @return true if this text frame ends with a newline character.  It
   * should return false if this is not a text frame.
   */
  virtual bool HasSignificantTerminalNewline() const;

  struct CaretPosition {
    CaretPosition();
    ~CaretPosition();

    nsCOMPtr<nsIContent> mResultContent;
    int32_t              mContentOffset;
  };

  /**
   * gets the first or last possible caret position within the frame
   *
   * @param  [in] aStart
   *         true  for getting the first possible caret position
   *         false for getting the last possible caret position
   * @return The caret position in a CaretPosition.
   *         the returned value is a 'best effort' in case errors
   *         are encountered rummaging through the frame.
   */
  CaretPosition GetExtremeCaretPosition(bool aStart);

  /**
   * Get a line iterator for this frame, if supported.
   *
   * @return nullptr if no line iterator is supported.
   * @note dispose the line iterator using nsILineIterator::DisposeLineIterator
   */
  virtual nsILineIterator* GetLineIterator() = 0;

  /**
   * If this frame is a next-in-flow, and its prev-in-flow has something on its
   * overflow list, pull those frames into the child list of this one.
   */
  virtual void PullOverflowsFromPrevInFlow() {}

  /**
   * Clear the list of child PresShells generated during the last paint
   * so that we can begin generating a new one.
   */  
  void ClearPresShellsFromLastPaint() { 
    PaintedPresShellList()->Clear(); 
  }
  
  /**
   * Flag a child PresShell as painted so that it will get its paint count
   * incremented during empty transactions.
   */  
  void AddPaintedPresShell(nsIPresShell* shell) { 
    PaintedPresShellList()->AppendElement(do_GetWeakReference(shell));
  }
  
  /**
   * Increment the paint count of all child PresShells that were painted during
   * the last repaint.
   */  
  void UpdatePaintCountForPaintedPresShells() {
    for (nsWeakPtr& item : *PaintedPresShellList()) {
      nsCOMPtr<nsIPresShell> shell = do_QueryReferent(item);
      if (shell) {
        shell->IncrementPaintCount();
      }
    }
  }  

  /**
   * @return true if we painted @aShell during the last repaint.
   */
  bool DidPaintPresShell(nsIPresShell* aShell)
  {
    for (nsWeakPtr& item : *PaintedPresShellList()) {
      nsCOMPtr<nsIPresShell> shell = do_QueryReferent(item);
      if (shell == aShell) {
        return true;
      }
    }
    return false;
  }

  /**
   * Accessors for the absolute containing block.
   */
  bool IsAbsoluteContainer() const { return !!(mState & NS_FRAME_HAS_ABSPOS_CHILDREN); }
  bool HasAbsolutelyPositionedChildren() const;
  nsAbsoluteContainingBlock* GetAbsoluteContainingBlock() const;
  void MarkAsAbsoluteContainingBlock();
  void MarkAsNotAbsoluteContainingBlock();
  // Child frame types override this function to select their own child list name
  virtual mozilla::layout::FrameChildListID GetAbsoluteListID() const { return kAbsoluteList; }

  // Checks if we (or any of our descendents) have NS_FRAME_PAINTED_THEBES set, and
  // clears this bit if so.
  bool CheckAndClearPaintedState();

  // CSS visibility just doesn't cut it because it doesn't inherit through
  // documents. Also if this frame is in a hidden card of a deck then it isn't
  // visible either and that isn't expressed using CSS visibility. Also if it
  // is in a hidden view (there are a few cases left and they are hopefully
  // going away soon).
  // If the VISIBILITY_CROSS_CHROME_CONTENT_BOUNDARY flag is passed then we
  // ignore the chrome/content boundary, otherwise we stop looking when we
  // reach it.
  enum {
    VISIBILITY_CROSS_CHROME_CONTENT_BOUNDARY = 0x01
  };
  bool IsVisibleConsideringAncestors(uint32_t aFlags = 0) const;

  struct FrameWithDistance
  {
    nsIFrame* mFrame;
    nscoord mXDistance;
    nscoord mYDistance;
  };

  /**
   * Finds a frame that is closer to a specified point than a current
   * distance.  Distance is measured as for text selection -- a closer x
   * distance beats a closer y distance.
   *
   * Normally, this function will only check the distance between this
   * frame's rectangle and the specified point.  SVGTextFrame overrides
   * this so that it can manage all of its descendant frames and take
   * into account any SVG text layout.
   *
   * If aPoint is closer to this frame's rectangle than aCurrentBestFrame
   * indicates, then aCurrentBestFrame is updated with the distance between
   * aPoint and this frame's rectangle, and with a pointer to this frame.
   * If aPoint is not closer, then aCurrentBestFrame is left unchanged.
   *
   * @param aPoint The point to check for its distance to this frame.
   * @param aCurrentBestFrame Pointer to a struct that will be updated with
   *   a pointer to this frame and its distance to aPoint, if this frame
   *   is indeed closer than the current distance in aCurrentBestFrame.
   */
  virtual void FindCloserFrameForSelection(nsPoint aPoint,
                                           FrameWithDistance* aCurrentBestFrame);

  /**
   * Is this a flex item? (i.e. a non-abs-pos child of a flex container)
   */
  inline bool IsFlexItem() const;
  /**
   * Is this a flex or grid item? (i.e. a non-abs-pos child of a flex/grid container)
   */
  inline bool IsFlexOrGridItem() const;
  inline bool IsFlexOrGridContainer() const;

  /**
   * @return true if this frame is used as a table caption.
   */
  inline bool IsTableCaption() const;

  inline bool IsBlockInside() const;
  inline bool IsBlockOutside() const;
  inline bool IsInlineOutside() const;
  inline mozilla::StyleDisplay GetDisplay() const;
  inline bool IsFloating() const;
  inline bool IsAbsPosContainingBlock() const;
  inline bool IsFixedPosContainingBlock() const;
  inline bool IsRelativelyPositioned() const;
  inline bool IsAbsolutelyPositioned() const;

  /**
   * Returns the vertical-align value to be used for layout, if it is one
   * of the enumerated values.  If this is an SVG text frame, it returns a value
   * that corresponds to the value of dominant-baseline.  If the
   * vertical-align property has length or percentage value, this returns
   * eInvalidVerticalAlign.
   */
  uint8_t VerticalAlignEnum() const;
  enum { eInvalidVerticalAlign = 0xFF };

  bool IsSVGText() const { return mState & NS_FRAME_IS_SVG_TEXT; }

  void CreateOwnLayerIfNeeded(nsDisplayListBuilder* aBuilder, nsDisplayList* aList);

  /**
   * Adds the NS_FRAME_IN_POPUP state bit to aFrame, and
   * all descendant frames (including cross-doc ones).
   */
  static void AddInPopupStateBitToDescendants(nsIFrame* aFrame);
  /**
   * Removes the NS_FRAME_IN_POPUP state bit from aFrame and
   * all descendant frames (including cross-doc ones), unless
   * the frame is a popup itself.
   */
  static void RemoveInPopupStateBitFromDescendants(nsIFrame* aFrame);

  /**
   * Sorts the given nsFrameList, so that for every two adjacent frames in the
   * list, the former is less than or equal to the latter, according to the
   * templated IsLessThanOrEqual method.
   *
   * Note: this method uses a stable merge-sort algorithm.
   */
  template<bool IsLessThanOrEqual(nsIFrame*, nsIFrame*)>
  static void SortFrameList(nsFrameList& aFrameList);

  /**
   * Returns true if the given frame list is already sorted, according to the
   * templated IsLessThanOrEqual function.
   */
  template<bool IsLessThanOrEqual(nsIFrame*, nsIFrame*)>
  static bool IsFrameListSorted(nsFrameList& aFrameList);

  /**
   * Return true if aFrame is in an {ib} split and is NOT one of the
   * continuations of the first inline in it.
   */
  bool FrameIsNonFirstInIBSplit() const {
    return (GetStateBits() & NS_FRAME_PART_OF_IBSPLIT) &&
      FirstContinuation()->GetProperty(nsIFrame::IBSplitPrevSibling());
  }

  /**
   * Return true if aFrame is in an {ib} split and is NOT one of the
   * continuations of the last inline in it.
   */
  bool FrameIsNonLastInIBSplit() const {
    return (GetStateBits() & NS_FRAME_PART_OF_IBSPLIT) &&
      FirstContinuation()->GetProperty(nsIFrame::IBSplitSibling());
  }

  /**
   * Return whether this is a frame whose width is used when computing
   * the font size inflation of its descendants.
   */
  bool IsContainerForFontSizeInflation() const {
    return GetStateBits() & NS_FRAME_FONT_INFLATION_CONTAINER;
  }

  /**
   * Return whether this frame keeps track of overflow areas. (Frames for
   * non-display SVG elements -- e.g. <clipPath> -- do not maintain overflow
   * areas, because they're never painted.)
   */
  bool FrameMaintainsOverflow() const {
    return !HasAllStateBits(NS_FRAME_SVG_LAYOUT | NS_FRAME_IS_NONDISPLAY);
  }

  /**
   * Returns the content node within the anonymous content that this frame
   * generated and which corresponds to the specified pseudo-element type,
   * or nullptr if there is no such anonymous content.
   */
  virtual mozilla::dom::Element*
  GetPseudoElement(mozilla::CSSPseudoElementType aType);

  bool BackfaceIsHidden() const {
    return StyleDisplay()->BackfaceIsHidden();
  }

  /**
   * Returns true if the frame is scrolled out of view.
   */
  bool IsScrolledOutOfView();

  /**
   * If this returns true, the frame it's called on should get the
   * NS_FRAME_HAS_DIRTY_CHILDREN bit set on it by the caller; either directly
   * if it's already in reflow, or via calling FrameNeedsReflow() to schedule a
   * reflow.
   */
  virtual bool RenumberFrameAndDescendants(int32_t* aOrdinal,
                                           int32_t aDepth,
                                           int32_t aIncrement,
                                           bool aForCounting) { return false; }

  /**
   * Helper function - computes the content-box inline size for aCoord.
   */
  nscoord ComputeISizeValue(nsRenderingContext* aRenderingContext,
                            nscoord             aContainingBlockISize,
                            nscoord             aContentEdgeToBoxSizing,
                            nscoord             aBoxSizingToMarginEdge,
                            const nsStyleCoord& aCoord,
                            ComputeSizeFlags    aFlags = eDefault);
protected:
  // Members
  nsRect           mRect;
  nsIContent*      mContent;
  nsStyleContext*  mStyleContext;
private:
  nsContainerFrame* mParent;
  nsIFrame*        mNextSibling;  // doubly-linked list of frames
  nsIFrame*        mPrevSibling;  // Do not touch outside SetNextSibling!

  void MarkAbsoluteFramesForDisplayList(nsDisplayListBuilder* aBuilder, const nsRect& aDirtyRect);

  static void DestroyPaintedPresShellList(nsTArray<nsWeakPtr>* list) {
    list->Clear();
    delete list;
  }

  // Stores weak references to all the PresShells that were painted during
  // the last paint event so that we can increment their paint count during
  // empty transactions
  NS_DECLARE_FRAME_PROPERTY_WITH_DTOR(PaintedPresShellsProperty,
                                      nsTArray<nsWeakPtr>,
                                      DestroyPaintedPresShellList)
  
  nsTArray<nsWeakPtr>* PaintedPresShellList() {
    nsTArray<nsWeakPtr>* list = GetProperty(PaintedPresShellsProperty());
    
    if (!list) {
      list = new nsTArray<nsWeakPtr>();
      SetProperty(PaintedPresShellsProperty(), list);
    }
    
    return list;
  }

protected:
  void MarkInReflow() {
#ifdef DEBUG_dbaron_off
    // bug 81268
    NS_ASSERTION(!(mState & NS_FRAME_IN_REFLOW), "frame is already in reflow");
#endif
    mState |= NS_FRAME_IN_REFLOW;
  }

  nsFrameState     mState;

 /**
  * List of properties attached to the frame.
  */
 FrameProperties  mProperties;

  // When there is an overflow area only slightly larger than mRect,
  // we store a set of four 1-byte deltas from the edges of mRect
  // rather than allocating a whole separate rectangle property.
  // Note that these are unsigned values, all measured "outwards"
  // from the edges of mRect, so /mLeft/ and /mTop/ are reversed from
  // our normal coordinate system.
  // If mOverflow.mType == NS_FRAME_OVERFLOW_LARGE, then the
  // delta values are not meaningful and the overflow area is stored
  // as a separate rect property.
  struct VisualDeltas {
    uint8_t mLeft;
    uint8_t mTop;
    uint8_t mRight;
    uint8_t mBottom;
    bool operator==(const VisualDeltas& aOther) const
    {
      return mLeft == aOther.mLeft && mTop == aOther.mTop &&
             mRight == aOther.mRight && mBottom == aOther.mBottom;
    }
    bool operator!=(const VisualDeltas& aOther) const
    {
      return !(*this == aOther);
    }
  };
  union {
    uint32_t     mType;
    VisualDeltas mVisualDeltas;
  } mOverflow;

  // Helpers
  /**
   * Can we stop inside this frame when we're skipping non-rendered whitespace?
   * @param  aForward [in] Are we moving forward (or backward) in content order.
   * @param  aOffset [in/out] At what offset into the frame to start looking.
   *         on output - what offset was reached (whether or not we found a place to stop).
   * @return STOP: An appropriate offset was found within this frame,
   *         and is given by aOffset.
   *         CONTINUE: Not found within this frame, need to try the next frame.
   *         see enum FrameSearchResult for more details.
   */
  virtual FrameSearchResult PeekOffsetNoAmount(bool aForward, int32_t* aOffset) = 0;
  
  /**
   * Search the frame for the next character
   * @param  aForward [in] Are we moving forward (or backward) in content order.
   * @param  aOffset [in/out] At what offset into the frame to start looking.
   *         on output - what offset was reached (whether or not we found a place to stop).
   * @param  aRespectClusters [in] Whether to restrict result to valid cursor locations
   *         (between grapheme clusters) - default TRUE maintains "normal" behavior,
   *         FALSE is used for selection by "code unit" (instead of "character")
   * @return STOP: An appropriate offset was found within this frame,
   *         and is given by aOffset.
   *         CONTINUE: Not found within this frame, need to try the next frame.
   *         see enum FrameSearchResult for more details.
   */
  virtual FrameSearchResult PeekOffsetCharacter(bool aForward, int32_t* aOffset,
                                     bool aRespectClusters = true) = 0;
  
  /**
   * Search the frame for the next word boundary
   * @param  aForward [in] Are we moving forward (or backward) in content order.
   * @param  aWordSelectEatSpace [in] true: look for non-whitespace following
   *         whitespace (in the direction of movement).
   *         false: look for whitespace following non-whitespace (in the
   *         direction  of movement).
   * @param  aIsKeyboardSelect [in] Was the action initiated by a keyboard operation?
   *         If true, punctuation immediately following a word is considered part
   *         of that word. Otherwise, a sequence of punctuation is always considered
   *         as a word on its own.
   * @param  aOffset [in/out] At what offset into the frame to start looking.
   *         on output - what offset was reached (whether or not we found a place to stop).
   * @param  aState [in/out] the state that is carried from frame to frame
   * @return true: An appropriate offset was found within this frame,
   *         and is given by aOffset.
   *         false: Not found within this frame, need to try the next frame.
   */
  struct PeekWordState {
    // true when we're still at the start of the search, i.e., we can't return
    // this point as a valid offset!
    bool mAtStart;
    // true when we've encountered at least one character of the pre-boundary type
    // (whitespace if aWordSelectEatSpace is true, non-whitespace otherwise)
    bool mSawBeforeType;
    // true when the last character encountered was punctuation
    bool mLastCharWasPunctuation;
    // true when the last character encountered was whitespace
    bool mLastCharWasWhitespace;
    // true when we've seen non-punctuation since the last whitespace
    bool mSeenNonPunctuationSinceWhitespace;
    // text that's *before* the current frame when aForward is true, *after*
    // the current frame when aForward is false. Only includes the text
    // on the current line.
    nsAutoString mContext;

    PeekWordState() : mAtStart(true), mSawBeforeType(false),
        mLastCharWasPunctuation(false), mLastCharWasWhitespace(false),
        mSeenNonPunctuationSinceWhitespace(false) {}
    void SetSawBeforeType() { mSawBeforeType = true; }
    void Update(bool aAfterPunctuation, bool aAfterWhitespace) {
      mLastCharWasPunctuation = aAfterPunctuation;
      mLastCharWasWhitespace = aAfterWhitespace;
      if (aAfterWhitespace) {
        mSeenNonPunctuationSinceWhitespace = false;
      } else if (!aAfterPunctuation) {
        mSeenNonPunctuationSinceWhitespace = true;
      }
      mAtStart = false;
    }
  };
  virtual FrameSearchResult PeekOffsetWord(bool aForward, bool aWordSelectEatSpace, bool aIsKeyboardSelect,
                                int32_t* aOffset, PeekWordState* aState) = 0;

  /**
   * Search for the first paragraph boundary before or after the given position
   * @param  aPos See description in nsFrameSelection.h. The following fields are
   *              used by this method: 
   *              Input: mDirection
   *              Output: mResultContent, mContentOffset
   */
  nsresult PeekOffsetParagraph(nsPeekOffsetStruct *aPos);

private:
  nsOverflowAreas* GetOverflowAreasProperty();
  nsRect GetVisualOverflowFromDeltas() const {
    MOZ_ASSERT(mOverflow.mType != NS_FRAME_OVERFLOW_LARGE,
               "should not be called when overflow is in a property");
    // Calculate the rect using deltas from the frame's border rect.
    // Note that the mOverflow.mDeltas fields are unsigned, but we will often
    // need to return negative values for the left and top, so take care
    // to cast away the unsigned-ness.
    return nsRect(-(int32_t)mOverflow.mVisualDeltas.mLeft,
                  -(int32_t)mOverflow.mVisualDeltas.mTop,
                  mRect.width + mOverflow.mVisualDeltas.mRight +
                                mOverflow.mVisualDeltas.mLeft,
                  mRect.height + mOverflow.mVisualDeltas.mBottom +
                                 mOverflow.mVisualDeltas.mTop);
  }
  /**
   * Returns true if any overflow changed.
   */
  bool SetOverflowAreas(const nsOverflowAreas& aOverflowAreas);

  // Helper-functions for SortFrameList():
  template<bool IsLessThanOrEqual(nsIFrame*, nsIFrame*)>
  static nsIFrame* SortedMerge(nsIFrame *aLeft, nsIFrame *aRight);

  template<bool IsLessThanOrEqual(nsIFrame*, nsIFrame*)>
  static nsIFrame* MergeSort(nsIFrame *aSource);

  bool HasOpacityInternal(float aThreshold) const;

#ifdef DEBUG_FRAME_DUMP
public:
  static void IndentBy(FILE* out, int32_t aIndent) {
    while (--aIndent >= 0) fputs("  ", out);
  }
  void ListTag(FILE* out) const {
    ListTag(out, this);
  }
  static void ListTag(FILE* out, const nsIFrame* aFrame) {
    nsAutoCString t;
    ListTag(t, aFrame);
    fputs(t.get(), out);
  }
  static void ListTag(FILE* out, const nsFrameList& aFrameList) {
    for (nsIFrame* frame : aFrameList) {
      ListTag(out, frame);
    }
  }
  void ListTag(nsACString& aTo) const;
  nsAutoCString ListTag() const {
    nsAutoCString tag;
    ListTag(tag);
    return tag;
  }
  static void ListTag(nsACString& aTo, const nsIFrame* aFrame);
  void ListGeneric(nsACString& aTo, const char* aPrefix = "", uint32_t aFlags = 0) const;
  enum {
    TRAVERSE_SUBDOCUMENT_FRAMES = 0x01
  };
  virtual void List(FILE* out = stderr, const char* aPrefix = "", uint32_t aFlags = 0) const;
  /**
   * lists the frames beginning from the root frame
   * - calls root frame's List(...)
   */
  static void RootFrameList(nsPresContext* aPresContext,
                            FILE* out = stderr, const char* aPrefix = "");
  virtual void DumpFrameTree() const;
  void DumpFrameTreeLimited() const;

  virtual nsresult  GetFrameName(nsAString& aResult) const = 0;
#endif

#ifdef DEBUG
public:
  virtual nsFrameState  GetDebugStateBits() const = 0;
  virtual nsresult  DumpRegressionData(nsPresContext* aPresContext,
                                       FILE* out, int32_t aIndent) = 0;
#endif
};

//----------------------------------------------------------------------

/**
 * nsWeakFrame can be used to keep a reference to a nsIFrame in a safe way.
 * Whenever an nsIFrame object is deleted, the nsWeakFrames pointing
 * to it will be cleared.
 *
 * Create nsWeakFrame object when it is sure that nsIFrame object
 * is alive and after some operations which may destroy the nsIFrame
 * (for example any DOM modifications) use IsAlive() or GetFrame() methods to
 * check whether it is safe to continue to use the nsIFrame object.
 *
 * @note The usage of this class should be kept to a minimum.
 */

class nsWeakFrame {
public:
  nsWeakFrame() : mPrev(nullptr), mFrame(nullptr) { }

  nsWeakFrame(const nsWeakFrame& aOther) : mPrev(nullptr), mFrame(nullptr)
  {
    Init(aOther.GetFrame());
  }

  MOZ_IMPLICIT nsWeakFrame(nsIFrame* aFrame) : mPrev(nullptr), mFrame(nullptr)
  {
    Init(aFrame);
  }

  nsWeakFrame& operator=(nsWeakFrame& aOther) {
    Init(aOther.GetFrame());
    return *this;
  }

  nsWeakFrame& operator=(nsIFrame* aFrame) {
    Init(aFrame);
    return *this;
  }

  nsIFrame* operator->()
  {
    return mFrame;
  }

  operator nsIFrame*()
  {
    return mFrame;
  }

  void Clear(nsIPresShell* aShell) {
    if (aShell) {
      aShell->RemoveWeakFrame(this);
    }
    mFrame = nullptr;
    mPrev = nullptr;
  }

  bool IsAlive() { return !!mFrame; }

  nsIFrame* GetFrame() const { return mFrame; }

  nsWeakFrame* GetPreviousWeakFrame() { return mPrev; }

  void SetPreviousWeakFrame(nsWeakFrame* aPrev) { mPrev = aPrev; }

  ~nsWeakFrame()
  {
    Clear(mFrame ? mFrame->PresContext()->GetPresShell() : nullptr);
  }
private:
  void Init(nsIFrame* aFrame);

  nsWeakFrame*  mPrev;
  nsIFrame*     mFrame;
};

inline bool
nsFrameList::ContinueRemoveFrame(nsIFrame* aFrame)
{
  MOZ_ASSERT(!aFrame->GetPrevSibling() || !aFrame->GetNextSibling(),
             "Forgot to call StartRemoveFrame?");
  if (aFrame == mLastChild) {
    MOZ_ASSERT(!aFrame->GetNextSibling(), "broken frame list");
    nsIFrame* prevSibling = aFrame->GetPrevSibling();
    if (!prevSibling) {
      MOZ_ASSERT(aFrame == mFirstChild, "broken frame list");
      mFirstChild = mLastChild = nullptr;
      return true;
    }
    MOZ_ASSERT(prevSibling->GetNextSibling() == aFrame, "Broken frame linkage");
    prevSibling->SetNextSibling(nullptr);
    mLastChild = prevSibling;
    return true;
  }
  if (aFrame == mFirstChild) {
    MOZ_ASSERT(!aFrame->GetPrevSibling(), "broken frame list");
    mFirstChild = aFrame->GetNextSibling();
    aFrame->SetNextSibling(nullptr);
    MOZ_ASSERT(mFirstChild, "broken frame list");
    return true;
  }
  return false;
}

inline bool
nsFrameList::StartRemoveFrame(nsIFrame* aFrame)
{
  if (aFrame->GetPrevSibling() && aFrame->GetNextSibling()) {
    UnhookFrameFromSiblings(aFrame);
    return true;
  }
  return ContinueRemoveFrame(aFrame);
}

inline void
nsFrameList::Enumerator::Next()
{
  NS_ASSERTION(!AtEnd(), "Should have checked AtEnd()!");
  mFrame = mFrame->GetNextSibling();
}

inline
nsFrameList::FrameLinkEnumerator::
FrameLinkEnumerator(const nsFrameList& aList, nsIFrame* aPrevFrame)
  : Enumerator(aList)
{
  mPrev = aPrevFrame;
  mFrame = aPrevFrame ? aPrevFrame->GetNextSibling() : aList.FirstChild();
}

inline void
nsFrameList::FrameLinkEnumerator::Next()
{
  mPrev = mFrame;
  Enumerator::Next();
}

// Operators of nsFrameList::Iterator
// ---------------------------------------------------

inline nsFrameList::Iterator&
nsFrameList::Iterator::operator++()
{
  mCurrent = mCurrent->GetNextSibling();
  return *this;
}

inline nsFrameList::Iterator&
nsFrameList::Iterator::operator--()
{
  if (!mCurrent) {
    mCurrent = mList.LastChild();
  } else {
    mCurrent = mCurrent->GetPrevSibling();
  }
  return *this;
}

// Helper-functions for nsIFrame::SortFrameList()
// ---------------------------------------------------

template<bool IsLessThanOrEqual(nsIFrame*, nsIFrame*)>
/* static */ nsIFrame*
nsIFrame::SortedMerge(nsIFrame *aLeft, nsIFrame *aRight)
{
  NS_PRECONDITION(aLeft && aRight, "SortedMerge must have non-empty lists");

  nsIFrame *result;
  // Unroll first iteration to avoid null-check 'result' inside the loop.
  if (IsLessThanOrEqual(aLeft, aRight)) {
    result = aLeft;
    aLeft = aLeft->GetNextSibling();
    if (!aLeft) {
      result->SetNextSibling(aRight);
      return result;
    }
  }
  else {
    result = aRight;
    aRight = aRight->GetNextSibling();
    if (!aRight) {
      result->SetNextSibling(aLeft);
      return result;
    }
  }

  nsIFrame *last = result;
  for (;;) {
    if (IsLessThanOrEqual(aLeft, aRight)) {
      last->SetNextSibling(aLeft);
      last = aLeft;
      aLeft = aLeft->GetNextSibling();
      if (!aLeft) {
        last->SetNextSibling(aRight);
        return result;
      }
    }
    else {
      last->SetNextSibling(aRight);
      last = aRight;
      aRight = aRight->GetNextSibling();
      if (!aRight) {
        last->SetNextSibling(aLeft);
        return result;
      }
    }
  }
}

template<bool IsLessThanOrEqual(nsIFrame*, nsIFrame*)>
/* static */ nsIFrame*
nsIFrame::MergeSort(nsIFrame *aSource)
{
  NS_PRECONDITION(aSource, "MergeSort null arg");

  nsIFrame *sorted[32] = { nullptr };
  nsIFrame **fill = &sorted[0];
  nsIFrame **left;
  nsIFrame *rest = aSource;

  do {
    nsIFrame *current = rest;
    rest = rest->GetNextSibling();
    current->SetNextSibling(nullptr);

    // Merge it with sorted[0] if present; then merge the result with sorted[1] etc.
    // sorted[0] is a list of length 1 (or nullptr).
    // sorted[1] is a list of length 2 (or nullptr).
    // sorted[2] is a list of length 4 (or nullptr). etc.
    for (left = &sorted[0]; left != fill && *left; ++left) {
      current = SortedMerge<IsLessThanOrEqual>(*left, current);
      *left = nullptr;
    }

    // Fill the empty slot that we couldn't merge with the last result.
    *left = current;

    if (left == fill)
      ++fill;
  } while (rest);

  // Collect and merge the results.
  nsIFrame *result = nullptr;
  for (left = &sorted[0]; left != fill; ++left) {
    if (*left) {
      result = result ? SortedMerge<IsLessThanOrEqual>(*left, result) : *left;
    }
  }
  return result;
}

template<bool IsLessThanOrEqual(nsIFrame*, nsIFrame*)>
/* static */ void
nsIFrame::SortFrameList(nsFrameList& aFrameList)
{
  nsIFrame* head = MergeSort<IsLessThanOrEqual>(aFrameList.FirstChild());
  aFrameList = nsFrameList(head, nsLayoutUtils::GetLastSibling(head));
  MOZ_ASSERT(IsFrameListSorted<IsLessThanOrEqual>(aFrameList),
             "After we sort a frame list, it should be in sorted order...");
}

template<bool IsLessThanOrEqual(nsIFrame*, nsIFrame*)>
/* static */ bool
nsIFrame::IsFrameListSorted(nsFrameList& aFrameList)
{
  if (aFrameList.IsEmpty()) {
    // empty lists are trivially sorted.
    return true;
  }

  // We'll walk through the list with two iterators, one trailing behind the
  // other. The list is sorted IFF trailingIter <= iter, across the whole list.
  nsFrameList::Enumerator trailingIter(aFrameList);
  nsFrameList::Enumerator iter(aFrameList);
  iter.Next(); // Skip |iter| past first frame. (List is nonempty, so we can.)

  // Now, advance the iterators in parallel, comparing each adjacent pair.
  while (!iter.AtEnd()) {
    MOZ_ASSERT(!trailingIter.AtEnd(), "trailing iter shouldn't finish first");
    if (!IsLessThanOrEqual(trailingIter.get(), iter.get())) {
      return false;
    }
    trailingIter.Next();
    iter.Next();
  }

  // We made it to the end without returning early, so the list is sorted.
  return true;
}

#endif /* nsIFrame_h___ */