summaryrefslogtreecommitdiffstats
path: root/gfx/thebes/gfxTextRun.h
blob: 7217eca747ec395cec619eaee83588da300a7a36 (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
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * 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/. */

#ifndef GFX_TEXTRUN_H
#define GFX_TEXTRUN_H

#include "gfxTypes.h"
#include "nsString.h"
#include "gfxPoint.h"
#include "gfxFont.h"
#include "gfxFont-Impl.h"
#include "gfxFontConstants.h"
#include "nsTArray.h"
#include "gfxSkipChars.h"
#include "gfxPlatform.h"
#include "mozilla/MemoryReporting.h"
#include "DrawMode.h"
#include "harfbuzz/hb.h"
#include "nsUnicodeScriptCodes.h"
#include "nsColor.h"

#ifdef DEBUG
#include <stdio.h>
#endif

class gfxContext;
class gfxFontGroup;
class gfxUserFontEntry;
class gfxUserFontSet;
class nsIAtom;
class nsILanguageAtomService;
class gfxMissingFontRecorder;

namespace mozilla {
class SVGContextPaint;
};

/**
 * Callback for Draw() to use when drawing text with mode
 * DrawMode::GLYPH_PATH.
 */
struct gfxTextRunDrawCallbacks {

    /**
     * Constructs a new DrawCallbacks object.
     *
     * @param aShouldPaintSVGGlyphs If true, SVG glyphs will be painted.  If
     *   false, SVG glyphs will not be painted; fallback plain glyphs are not
     *   emitted either.
     */
    explicit gfxTextRunDrawCallbacks(bool aShouldPaintSVGGlyphs = false)
      : mShouldPaintSVGGlyphs(aShouldPaintSVGGlyphs)
    {
    }

    /**
     * Called when a path has been emitted to the gfxContext when
     * painting a text run.  This can be called any number of times,
     * due to partial ligatures and intervening SVG glyphs.
     */
    virtual void NotifyGlyphPathEmitted() = 0;

    bool mShouldPaintSVGGlyphs;
};

/**
 * gfxTextRun is an abstraction for drawing and measuring substrings of a run
 * of text. It stores runs of positioned glyph data, each run having a single
 * gfxFont. The glyphs are associated with a string of source text, and the
 * gfxTextRun APIs take parameters that are offsets into that source text.
 * 
 * gfxTextRuns are mostly immutable. The only things that can change are
 * inter-cluster spacing and line break placement. Spacing is always obtained
 * lazily by methods that need it, it is not cached. Line breaks are stored
 * persistently (insofar as they affect the shaping of glyphs; gfxTextRun does
 * not actually do anything to explicitly account for line breaks). Initially
 * there are no line breaks. The textrun can record line breaks before or after
 * any given cluster. (Line breaks specified inside clusters are ignored.)
 * 
 * It is important that zero-length substrings are handled correctly. This will
 * be on the test!
 */
class gfxTextRun : public gfxShapedText
{
    NS_INLINE_DECL_REFCOUNTING(gfxTextRun);

protected:
    // Override operator delete to properly free the object that was
    // allocated via malloc.
    void operator delete(void* p) {
        free(p);
    }

    virtual ~gfxTextRun();

public:
    typedef gfxFont::RunMetrics Metrics;
    typedef mozilla::gfx::DrawTarget DrawTarget;

    // Public textrun API for general use

    bool IsClusterStart(uint32_t aPos) const {
        MOZ_ASSERT(aPos < GetLength());
        return mCharacterGlyphs[aPos].IsClusterStart();
    }
    bool IsLigatureGroupStart(uint32_t aPos) const {
        MOZ_ASSERT(aPos < GetLength());
        return mCharacterGlyphs[aPos].IsLigatureGroupStart();
    }
    bool CanBreakLineBefore(uint32_t aPos) const {
        return CanBreakBefore(aPos) == CompressedGlyph::FLAG_BREAK_TYPE_NORMAL;
    }
    bool CanHyphenateBefore(uint32_t aPos) const {
        return CanBreakBefore(aPos) == CompressedGlyph::FLAG_BREAK_TYPE_HYPHEN;
    }

    // Returns a gfxShapedText::CompressedGlyph::FLAG_BREAK_TYPE_* value
    // as defined in gfxFont.h (may be NONE, NORMAL or HYPHEN).
    uint8_t CanBreakBefore(uint32_t aPos) const {
        MOZ_ASSERT(aPos < GetLength());
        return mCharacterGlyphs[aPos].CanBreakBefore();
    }

    bool CharIsSpace(uint32_t aPos) const {
        MOZ_ASSERT(aPos < GetLength());
        return mCharacterGlyphs[aPos].CharIsSpace();
    }
    bool CharIsTab(uint32_t aPos) const {
        MOZ_ASSERT(aPos < GetLength());
        return mCharacterGlyphs[aPos].CharIsTab();
    }
    bool CharIsNewline(uint32_t aPos) const {
        MOZ_ASSERT(aPos < GetLength());
        return mCharacterGlyphs[aPos].CharIsNewline();
    }
    bool CharMayHaveEmphasisMark(uint32_t aPos) const {
        MOZ_ASSERT(aPos < GetLength());
        return mCharacterGlyphs[aPos].CharMayHaveEmphasisMark();
    }

    // All offsets are in terms of the string passed into MakeTextRun.

    // Describe range [start, end) of a text run. The range is
    // restricted to grapheme cluster boundaries.
    struct Range
    {
        uint32_t start;
        uint32_t end;
        uint32_t Length() const { return end - start; }

        Range() : start(0), end(0) {}
        Range(uint32_t aStart, uint32_t aEnd)
            : start(aStart), end(aEnd) {}
        explicit Range(const gfxTextRun* aTextRun)
            : start(0), end(aTextRun->GetLength()) {}
    };

    // All coordinates are in layout/app units

    /**
     * Set the potential linebreaks for a substring of the textrun. These are
     * the "allow break before" points. Initially, there are no potential
     * linebreaks.
     * 
     * This can change glyphs and/or geometry! Some textruns' shapes
     * depend on potential line breaks (e.g., title-case-converting textruns).
     * This function is virtual so that those textruns can reshape themselves.
     * 
     * @return true if this changed the linebreaks, false if the new line
     * breaks are the same as the old
     */
    virtual bool SetPotentialLineBreaks(Range aRange,
                                        const uint8_t* aBreakBefore);

    /**
     * Layout provides PropertyProvider objects. These allow detection of
     * potential line break points and computation of spacing. We pass the data
     * this way to allow lazy data acquisition; for example BreakAndMeasureText
     * will want to only ask for properties of text it's actually looking at.
     * 
     * NOTE that requested spacing may not actually be applied, if the textrun
     * is unable to apply it in some context. Exception: spacing around a
     * whitespace character MUST always be applied.
     */
    class PropertyProvider {
    public:
        // Detect hyphenation break opportunities in the given range; breaks
        // not at cluster boundaries will be ignored.
        virtual void GetHyphenationBreaks(Range aRange, bool *aBreakBefore) = 0;

        // Returns the provider's hyphenation setting, so callers can decide
        // whether it is necessary to call GetHyphenationBreaks.
        // Result is an NS_STYLE_HYPHENS_* value.
        virtual int8_t GetHyphensOption() = 0;

        // Returns the extra width that will be consumed by a hyphen. This should
        // be constant for a given textrun.
        virtual gfxFloat GetHyphenWidth() = 0;

        typedef gfxFont::Spacing Spacing;

        /**
         * Get the spacing around the indicated characters. Spacing must be zero
         * inside clusters. In other words, if character i is not
         * CLUSTER_START, then character i-1 must have zero after-spacing and
         * character i must have zero before-spacing.
         */
        virtual void GetSpacing(Range aRange, Spacing *aSpacing) = 0;

        // Returns a gfxContext that can be used to measure the hyphen glyph.
        // Only called if the hyphen width is requested.
        virtual already_AddRefed<DrawTarget> GetDrawTarget() = 0;

        // Return the appUnitsPerDevUnit value to be used when measuring.
        // Only called if the hyphen width is requested.
        virtual uint32_t GetAppUnitsPerDevUnit() = 0;
    };

    struct DrawParams
    {
        gfxContext* context;
        DrawMode drawMode = DrawMode::GLYPH_FILL;
        nscolor textStrokeColor = 0;
        gfxPattern* textStrokePattern = nullptr;
        const mozilla::gfx::StrokeOptions *strokeOpts = nullptr;
        const mozilla::gfx::DrawOptions *drawOpts = nullptr;
        PropertyProvider* provider = nullptr;
        // If non-null, the advance width of the substring is set.
        gfxFloat* advanceWidth = nullptr;
        mozilla::SVGContextPaint* contextPaint = nullptr;
        gfxTextRunDrawCallbacks* callbacks = nullptr;
        explicit DrawParams(gfxContext* aContext) : context(aContext) {}
    };

    /**
     * Draws a substring. Uses only GetSpacing from aBreakProvider.
     * The provided point is the baseline origin on the left of the string
     * for LTR, on the right of the string for RTL.
     * 
     * Drawing should respect advance widths in the sense that for LTR runs,
     *   Draw(Range(start, middle), pt, ...) followed by
     *   Draw(Range(middle, end), gfxPoint(pt.x + advance, pt.y), ...)
     * should have the same effect as
     *   Draw(Range(start, end), pt, ...)
     *
     * For RTL runs the rule is:
     *   Draw(Range(middle, end), pt, ...) followed by
     *   Draw(Range(start, middle), gfxPoint(pt.x + advance, pt.y), ...)
     * should have the same effect as
     *   Draw(Range(start, end), pt, ...)
     * 
     * Glyphs should be drawn in logical content order, which can be significant
     * if they overlap (perhaps due to negative spacing).
     */
    void Draw(Range aRange, gfxPoint aPt, const DrawParams& aParams) const;

    /**
     * Draws the emphasis marks for this text run. Uses only GetSpacing
     * from aProvider. The provided point is the baseline origin of the
     * line of emphasis marks.
     */
    void DrawEmphasisMarks(gfxContext* aContext, gfxTextRun* aMark,
                           gfxFloat aMarkAdvance, gfxPoint aPt,
                           Range aRange, PropertyProvider* aProvider) const;

    /**
     * Computes the ReflowMetrics for a substring.
     * Uses GetSpacing from aBreakProvider.
     * @param aBoundingBoxType which kind of bounding box (loose/tight)
     */
    Metrics MeasureText(Range aRange,
                        gfxFont::BoundingBoxType aBoundingBoxType,
                        DrawTarget* aDrawTargetForTightBoundingBox,
                        PropertyProvider* aProvider) const;

    Metrics MeasureText(gfxFont::BoundingBoxType aBoundingBoxType,
                        DrawTarget* aDrawTargetForTightBoundingBox,
                        PropertyProvider* aProvider = nullptr) const {
        return MeasureText(Range(this), aBoundingBoxType,
                           aDrawTargetForTightBoundingBox, aProvider);
    }

    /**
     * Computes just the advance width for a substring.
     * Uses GetSpacing from aBreakProvider.
     * If aSpacing is not null, the spacing attached before and after
     * the substring would be returned in it. NOTE: the spacing is
     * included in the advance width.
     */
    gfxFloat GetAdvanceWidth(Range aRange, PropertyProvider *aProvider,
                             PropertyProvider::Spacing*
                                 aSpacing = nullptr) const;

    gfxFloat GetAdvanceWidth() const {
        return GetAdvanceWidth(Range(this), nullptr);
    }

    /**
     * Computes the minimum advance width for a substring assuming line
     * breaking is allowed everywhere.
     */
    gfxFloat GetMinAdvanceWidth(Range aRange);

    /**
     * Clear all stored line breaks for the given range (both before and after),
     * and then set the line-break state before aRange.start to aBreakBefore and
     * after the last cluster to aBreakAfter.
     * 
     * We require that before and after line breaks be consistent. For clusters
     * i and i+1, we require that if there is a break after cluster i, a break
     * will be specified before cluster i+1. This may be temporarily violated
     * (e.g. after reflowing line L and before reflowing line L+1); to handle
     * these temporary violations, we say that there is a break betwen i and i+1
     * if a break is specified after i OR a break is specified before i+1.
     * 
     * This can change textrun geometry! The existence of a linebreak can affect
     * the advance width of the cluster before the break (when kerning) or the
     * geometry of one cluster before the break or any number of clusters
     * after the break. (The one-cluster-before-the-break limit is somewhat
     * arbitrary; if some scripts require breaking it, then we need to
     * alter nsTextFrame::TrimTrailingWhitespace, perhaps drastically becase
     * it could affect the layout of frames before it...)
     * 
     * We return true if glyphs or geometry changed, false otherwise. This
     * function is virtual so that gfxTextRun subclasses can reshape
     * properly.
     * 
     * @param aAdvanceWidthDelta if non-null, returns the change in advance
     * width of the given range.
     */
    virtual bool SetLineBreaks(Range aRange,
                               bool aLineBreakBefore, bool aLineBreakAfter,
                               gfxFloat* aAdvanceWidthDelta);

    enum SuppressBreak {
      eNoSuppressBreak,
      // Measure the range of text as if there is no break before it.
      eSuppressInitialBreak,
      // Measure the range of text as if it contains no break
      eSuppressAllBreaks
    };

    /**
     * Finds the longest substring that will fit into the given width.
     * Uses GetHyphenationBreaks and GetSpacing from aBreakProvider.
     * Guarantees the following:
     * -- 0 <= result <= aMaxLength
     * -- result is the maximal value of N such that either
     *       N < aMaxLength && line break at N && GetAdvanceWidth(aStart, N) <= aWidth
     *   OR  N < aMaxLength && hyphen break at N && GetAdvanceWidth(aStart, N) + GetHyphenWidth() <= aWidth
     *   OR  N == aMaxLength && GetAdvanceWidth(aStart, N) <= aWidth
     * where GetAdvanceWidth assumes the effect of
     * SetLineBreaks(aStart, N, aLineBreakBefore, N < aMaxLength, aProvider)
     * -- if no such N exists, then result is the smallest N such that
     *       N < aMaxLength && line break at N
     *   OR  N < aMaxLength && hyphen break at N
     *   OR  N == aMaxLength
     *
     * The call has the effect of
     * SetLineBreaks(aStart, result, aLineBreakBefore, result < aMaxLength, aProvider)
     * and the returned metrics and the invariants above reflect this.
     *
     * @param aMaxLength this can be UINT32_MAX, in which case the length used
     * is up to the end of the string
     * @param aLineBreakBefore set to true if and only if there is an actual
     * line break at the start of this string.
     * @param aSuppressBreak what break should be suppressed.
     * @param aTrimWhitespace if non-null, then we allow a trailing run of
     * spaces to be trimmed; the width of the space(s) will not be included in
     * the measured string width for comparison with the limit aWidth, and
     * trimmed spaces will not be included in returned metrics. The width
     * of the trimmed spaces will be returned in aTrimWhitespace.
     * Trimmed spaces are still counted in the "characters fit" result.
     * @param aMetrics if non-null, we fill this in for the returned substring.
     * If a hyphenation break was used, the hyphen is NOT included in the returned metrics.
     * @param aBoundingBoxType whether to make the bounding box in aMetrics tight
     * @param aDrawTargetForTightBoundingbox a reference DrawTarget to get the
     * tight bounding box, if requested
     * @param aUsedHyphenation if non-null, records if we selected a hyphenation break
     * @param aLastBreak if non-null and result is aMaxLength, we set this to
     * the maximal N such that
     *       N < aMaxLength && line break at N && GetAdvanceWidth(aStart, N) <= aWidth
     *   OR  N < aMaxLength && hyphen break at N && GetAdvanceWidth(aStart, N) + GetHyphenWidth() <= aWidth
     * or UINT32_MAX if no such N exists, where GetAdvanceWidth assumes
     * the effect of
     * SetLineBreaks(aStart, N, aLineBreakBefore, N < aMaxLength, aProvider)
     *
     * @param aCanWordWrap true if we can break between any two grapheme
     * clusters. This is set by overflow-wrap|word-wrap: break-word
     *
     * @param aBreakPriority in/out the priority of the break opportunity
     * saved in the line. If we are prioritizing break opportunities, we will
     * not set a break with a lower priority. @see gfxBreakPriority.
     * 
     * Note that negative advance widths are possible especially if negative
     * spacing is provided.
     */
    uint32_t BreakAndMeasureText(uint32_t aStart, uint32_t aMaxLength,
                                 bool aLineBreakBefore, gfxFloat aWidth,
                                 PropertyProvider *aProvider,
                                 SuppressBreak aSuppressBreak,
                                 gfxFloat *aTrimWhitespace,
                                 bool aHangWhitespace,
                                 Metrics *aMetrics,
                                 gfxFont::BoundingBoxType aBoundingBoxType,
                                 DrawTarget* aDrawTargetForTightBoundingBox,
                                 bool *aUsedHyphenation,
                                 uint32_t *aLastBreak,
                                 bool aCanWordWrap,
                                 gfxBreakPriority *aBreakPriority);

    // Utility getters

    void *GetUserData() const { return mUserData; }
    void SetUserData(void *aUserData) { mUserData = aUserData; }

    void SetFlagBits(uint32_t aFlags) {
      NS_ASSERTION(!(aFlags & ~gfxTextRunFactory::SETTABLE_FLAGS),
                   "Only user flags should be mutable");
      mFlags |= aFlags;
    }
    void ClearFlagBits(uint32_t aFlags) {
      NS_ASSERTION(!(aFlags & ~gfxTextRunFactory::SETTABLE_FLAGS),
                   "Only user flags should be mutable");
      mFlags &= ~aFlags;
    }
    const gfxSkipChars& GetSkipChars() const { return mSkipChars; }
    gfxFontGroup *GetFontGroup() const { return mFontGroup; }


    // Call this, don't call "new gfxTextRun" directly. This does custom
    // allocation and initialization
    static already_AddRefed<gfxTextRun>
    Create(const gfxTextRunFactory::Parameters *aParams,
           uint32_t aLength, gfxFontGroup *aFontGroup,
           uint32_t aFlags);

    // The text is divided into GlyphRuns as necessary
    struct GlyphRun {
        RefPtr<gfxFont> mFont;   // never null
        uint32_t          mCharacterOffset; // into original UTF16 string
        uint8_t           mMatchType;
        uint16_t          mOrientation; // gfxTextRunFactory::TEXT_ORIENT_* value
    };

    class GlyphRunIterator {
    public:
        GlyphRunIterator(const gfxTextRun *aTextRun, Range aRange)
          : mTextRun(aTextRun)
          , mStartOffset(aRange.start)
          , mEndOffset(aRange.end) {
            mNextIndex = mTextRun->FindFirstGlyphRunContaining(aRange.start);
        }
        bool NextRun();
        const GlyphRun *GetGlyphRun() const { return mGlyphRun; }
        uint32_t GetStringStart() const { return mStringStart; }
        uint32_t GetStringEnd() const { return mStringEnd; }
    private:
        const gfxTextRun *mTextRun;
        MOZ_INIT_OUTSIDE_CTOR const GlyphRun   *mGlyphRun;
        MOZ_INIT_OUTSIDE_CTOR uint32_t    mStringStart;
        MOZ_INIT_OUTSIDE_CTOR uint32_t    mStringEnd;
        uint32_t    mNextIndex;
        uint32_t    mStartOffset;
        uint32_t    mEndOffset;
    };

    class GlyphRunOffsetComparator {
    public:
        bool Equals(const GlyphRun& a,
                      const GlyphRun& b) const
        {
            return a.mCharacterOffset == b.mCharacterOffset;
        }

        bool LessThan(const GlyphRun& a,
                        const GlyphRun& b) const
        {
            return a.mCharacterOffset < b.mCharacterOffset;
        }
    };

    friend class GlyphRunIterator;
    friend class FontSelector;

    // API for setting up the textrun glyphs. Should only be called by
    // things that construct textruns.
    /**
     * We've found a run of text that should use a particular font. Call this
     * only during initialization when font substitution has been computed.
     * Call it before setting up the glyphs for the characters in this run;
     * SetMissingGlyph requires that the correct glyphrun be installed.
     *
     * If aForceNewRun, a new glyph run will be added, even if the
     * previously added run uses the same font.  If glyph runs are
     * added out of strictly increasing aStartCharIndex order (via
     * force), then SortGlyphRuns must be called after all glyph runs
     * are added before any further operations are performed with this
     * TextRun.
     */
    nsresult AddGlyphRun(gfxFont *aFont, uint8_t aMatchType,
                         uint32_t aStartCharIndex, bool aForceNewRun,
                         uint16_t aOrientation);
    void ResetGlyphRuns() { mGlyphRuns.Clear(); }
    void SortGlyphRuns();
    void SanitizeGlyphRuns();

    const CompressedGlyph* GetCharacterGlyphs() const final {
        MOZ_ASSERT(mCharacterGlyphs, "failed to initialize mCharacterGlyphs");
        return mCharacterGlyphs;
    }
    CompressedGlyph* GetCharacterGlyphs() final {
        MOZ_ASSERT(mCharacterGlyphs, "failed to initialize mCharacterGlyphs");
        return mCharacterGlyphs;
    }

    // clean out results from shaping in progress, used for fallback scenarios
    void ClearGlyphsAndCharacters();

    void SetSpaceGlyph(gfxFont* aFont, DrawTarget* aDrawTarget,
                       uint32_t aCharIndex, uint16_t aOrientation);

    // Set the glyph data for the given character index to the font's
    // space glyph, IF this can be done as a "simple" glyph record
    // (not requiring a DetailedGlyph entry). This avoids the need to call
    // the font shaper and go through the shaped-word cache for most spaces.
    //
    // The parameter aSpaceChar is the original character code for which
    // this space glyph is being used; if this is U+0020, we need to record
    // that it could be trimmed at a run edge, whereas other kinds of space
    // (currently just U+00A0) would not be trimmable/breakable.
    //
    // Returns true if it was able to set simple glyph data for the space;
    // if it returns false, the caller needs to fall back to some other
    // means to create the necessary (detailed) glyph data.
    bool SetSpaceGlyphIfSimple(gfxFont *aFont, uint32_t aCharIndex,
                               char16_t aSpaceChar, uint16_t aOrientation);

    // Record the positions of specific characters that layout may need to
    // detect in the textrun, even though it doesn't have an explicit copy
    // of the original text. These are recorded using flag bits in the
    // CompressedGlyph record; if necessary, we convert "simple" glyph records
    // to "complex" ones as the Tab and Newline flags are not present in
    // simple CompressedGlyph records.
    void SetIsTab(uint32_t aIndex) {
        EnsureComplexGlyph(aIndex).SetIsTab();
    }
    void SetIsNewline(uint32_t aIndex) {
        EnsureComplexGlyph(aIndex).SetIsNewline();
    }
    void SetNoEmphasisMark(uint32_t aIndex) {
        EnsureComplexGlyph(aIndex).SetNoEmphasisMark();
    }

    /**
     * Prefetch all the glyph extents needed to ensure that Measure calls
     * on this textrun not requesting tight boundingBoxes will succeed. Note
     * that some glyph extents might not be fetched due to OOM or other
     * errors.
     */
    void FetchGlyphExtents(DrawTarget* aRefDrawTarget);

    uint32_t CountMissingGlyphs() const;
    const GlyphRun* GetGlyphRuns(uint32_t* aNumGlyphRuns) const {
        *aNumGlyphRuns = mGlyphRuns.Length();
        return mGlyphRuns.Elements();
    }
    // Returns the index of the GlyphRun containing the given offset.
    // Returns mGlyphRuns.Length() when aOffset is mCharacterCount.
    uint32_t FindFirstGlyphRunContaining(uint32_t aOffset) const;

    // Copy glyph data from a ShapedWord into this textrun.
    void CopyGlyphDataFrom(gfxShapedWord *aSource, uint32_t aStart);

    // Copy glyph data for a range of characters from aSource to this
    // textrun.
    void CopyGlyphDataFrom(gfxTextRun *aSource, Range aRange, uint32_t aDest);

    // Tell the textrun to release its reference to its creating gfxFontGroup
    // immediately, rather than on destruction. This is used for textruns
    // that are actually owned by a gfxFontGroup, so that they don't keep it
    // permanently alive due to a circular reference. (The caller of this is
    // taking responsibility for ensuring the textrun will not outlive its
    // mFontGroup.)
    void ReleaseFontGroup();

    struct LigatureData {
        // textrun range of the containing ligature
        Range mRange;
        // appunits advance to the start of the ligature part within the ligature;
        // never includes any spacing
        gfxFloat mPartAdvance;
        // appunits width of the ligature part; includes before-spacing
        // when the part is at the start of the ligature, and after-spacing
        // when the part is as the end of the ligature
        gfxFloat mPartWidth;
        
        bool mClipBeforePart;
        bool mClipAfterPart;
    };
    
    // return storage used by this run, for memory reporter;
    // nsTransformedTextRun needs to override this as it holds additional data
    virtual size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf)
      MOZ_MUST_OVERRIDE;
    virtual size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf)
      MOZ_MUST_OVERRIDE;

    // Get the size, if it hasn't already been gotten, marking as it goes.
    size_t MaybeSizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf)  {
        if (mFlags & gfxTextRunFactory::TEXT_RUN_SIZE_ACCOUNTED) {
            return 0;
        }
        mFlags |= gfxTextRunFactory::TEXT_RUN_SIZE_ACCOUNTED;
        return SizeOfIncludingThis(aMallocSizeOf);
    }
    void ResetSizeOfAccountingFlags() {
        mFlags &= ~gfxTextRunFactory::TEXT_RUN_SIZE_ACCOUNTED;
    }

    // shaping state - for some font features, fallback is required that
    // affects the entire run. for example, fallback for one script/font
    // portion of a textrun requires fallback to be applied to the entire run

    enum ShapingState {
        eShapingState_Normal,                 // default state
        eShapingState_ShapingWithFeature,     // have shaped with feature
        eShapingState_ShapingWithFallback,    // have shaped with fallback
        eShapingState_Aborted,                // abort initial iteration
        eShapingState_ForceFallbackFeature    // redo with fallback forced on
    };

    ShapingState GetShapingState() const { return mShapingState; }
    void SetShapingState(ShapingState aShapingState) {
        mShapingState = aShapingState;
    }

    int32_t GetAdvanceForGlyph(uint32_t aIndex) const
    {
        const CompressedGlyph& glyphData = mCharacterGlyphs[aIndex];
        if (glyphData.IsSimpleGlyph()) {
            return glyphData.GetSimpleAdvance();
        }
        uint32_t glyphCount = glyphData.GetGlyphCount();
        if (!glyphCount) {
            return 0;
        }
        const DetailedGlyph* details = GetDetailedGlyphs(aIndex);
        int32_t advance = 0;
        for (uint32_t j = 0; j < glyphCount; ++j, ++details) {
            advance += details->mAdvance;
        }
        return advance;
    }

#ifdef DEBUG
    void Dump(FILE* aOutput);
#endif

protected:
    /**
     * Create a textrun, and set its mCharacterGlyphs to point immediately
     * after the base object; this is ONLY used in conjunction with placement
     * new, after allocating a block large enough for the glyph records to
     * follow the base textrun object.
     */
    gfxTextRun(const gfxTextRunFactory::Parameters *aParams,
               uint32_t aLength, gfxFontGroup *aFontGroup, uint32_t aFlags);

    /**
     * Helper for the Create() factory method to allocate the required
     * glyph storage for a textrun object with the basic size aSize,
     * plus room for aLength glyph records.
     */
    static void* AllocateStorageForTextRun(size_t aSize, uint32_t aLength);

    // Pointer to the array of CompressedGlyph records; must be initialized
    // when the object is constructed.
    CompressedGlyph *mCharacterGlyphs;

private:
    // **** general helpers **** 

    // Get the total advance for a range of glyphs.
    int32_t GetAdvanceForGlyphs(Range aRange) const;

    // Spacing for characters outside the range aSpacingStart/aSpacingEnd
    // is assumed to be zero; such characters are not passed to aProvider.
    // This is useful to protect aProvider from being passed character indices
    // it is not currently able to handle.
    bool GetAdjustedSpacingArray(Range aRange, PropertyProvider *aProvider,
                                 Range aSpacingRange,
                                 nsTArray<PropertyProvider::Spacing>*
                                     aSpacing) const;

    CompressedGlyph& EnsureComplexGlyph(uint32_t aIndex)
    {
        gfxShapedText::EnsureComplexGlyph(aIndex, mCharacterGlyphs[aIndex]);
        return mCharacterGlyphs[aIndex];
    }

    //  **** ligature helpers ****
    // (Platforms do the actual ligaturization, but we need to do a bunch of stuff
    // to handle requests that begin or end inside a ligature)

    // if aProvider is null then mBeforeSpacing and mAfterSpacing are set to zero
    LigatureData ComputeLigatureData(Range aPartRange,
                                     PropertyProvider *aProvider) const;
    gfxFloat ComputePartialLigatureWidth(Range aPartRange,
                                         PropertyProvider *aProvider) const;
    void DrawPartialLigature(gfxFont *aFont, Range aRange,
                             gfxPoint *aPt, PropertyProvider *aProvider,
                             TextRunDrawParams& aParams,
                             uint16_t aOrientation) const;
    // Advance aRange.start to the start of the nearest ligature, back
    // up aRange.end to the nearest ligature end; may result in
    // aRange->start == aRange->end.
    void ShrinkToLigatureBoundaries(Range* aRange) const;
    // result in appunits
    gfxFloat GetPartialLigatureWidth(Range aRange,
                                     PropertyProvider *aProvider) const;
    void AccumulatePartialLigatureMetrics(gfxFont *aFont, Range aRange,
                                          gfxFont::BoundingBoxType aBoundingBoxType,
                                          DrawTarget* aRefDrawTarget,
                                          PropertyProvider *aProvider,
                                          uint16_t aOrientation,
                                          Metrics *aMetrics) const;

    // **** measurement helper ****
    void AccumulateMetricsForRun(gfxFont *aFont, Range aRange,
                                 gfxFont::BoundingBoxType aBoundingBoxType,
                                 DrawTarget* aRefDrawTarget,
                                 PropertyProvider *aProvider,
                                 Range aSpacingRange,
                                 uint16_t aOrientation,
                                 Metrics *aMetrics) const;

    // **** drawing helper ****
    void DrawGlyphs(gfxFont *aFont, Range aRange, gfxPoint *aPt,
                    PropertyProvider *aProvider, Range aSpacingRange,
                    TextRunDrawParams& aParams, uint16_t aOrientation) const;

    // XXX this should be changed to a GlyphRun plus a maybe-null GlyphRun*,
    // for smaller size especially in the super-common one-glyphrun case
    AutoTArray<GlyphRun,1>        mGlyphRuns;

    void             *mUserData;
    gfxFontGroup     *mFontGroup; // addrefed on creation, but our reference
                                  // may be released by ReleaseFontGroup()
    gfxSkipChars      mSkipChars;

    bool              mSkipDrawing; // true if the font group we used had a user font
                                    // download that's in progress, so we should hide text
                                    // until the download completes (or timeout fires)
    bool              mReleasedFontGroup; // we already called NS_RELEASE on
                                          // mFontGroup, so don't do it again

    // shaping state for handling variant fallback features
    // such as subscript/superscript variant glyphs
    ShapingState      mShapingState;
};

class gfxFontGroup : public gfxTextRunFactory {
public:
    typedef mozilla::unicode::Script Script;

    static void Shutdown(); // platform must call this to release the languageAtomService

    gfxFontGroup(const mozilla::FontFamilyList& aFontFamilyList,
                 const gfxFontStyle* aStyle,
                 gfxTextPerfMetrics* aTextPerf,
                 gfxUserFontSet* aUserFontSet,
                 gfxFloat aDevToCssSize);

    virtual ~gfxFontGroup();

    // Returns first valid font in the fontlist or default font.
    // Initiates userfont loads if userfont not loaded
    virtual gfxFont* GetFirstValidFont(uint32_t aCh = 0x20);

    // Returns the first font in the font-group that has an OpenType MATH table,
    // or null if no such font is available. The GetMathConstant methods may be
    // called on the returned font.
    gfxFont *GetFirstMathFont();

    const gfxFontStyle *GetStyle() const { return &mStyle; }

    virtual gfxFontGroup *Copy(const gfxFontStyle *aStyle);

    /**
     * The listed characters should be treated as invisible and zero-width
     * when creating textruns.
     */
    static bool IsInvalidChar(uint8_t ch);
    static bool IsInvalidChar(char16_t ch);

    /**
     * Make a textrun for a given string.
     * If aText is not persistent (aFlags & TEXT_IS_PERSISTENT), the
     * textrun will copy it.
     * This calls FetchGlyphExtents on the textrun.
     */
    virtual already_AddRefed<gfxTextRun>
    MakeTextRun(const char16_t *aString, uint32_t aLength,
                const Parameters *aParams, uint32_t aFlags,
                gfxMissingFontRecorder *aMFR);
    /**
     * Make a textrun for a given string.
     * If aText is not persistent (aFlags & TEXT_IS_PERSISTENT), the
     * textrun will copy it.
     * This calls FetchGlyphExtents on the textrun.
     */
    virtual already_AddRefed<gfxTextRun>
    MakeTextRun(const uint8_t *aString, uint32_t aLength,
                const Parameters *aParams, uint32_t aFlags,
                gfxMissingFontRecorder *aMFR);

    /**
     * Textrun creation helper for clients that don't want to pass
     * a full Parameters record.
     */
    template<typename T>
    already_AddRefed<gfxTextRun>
    MakeTextRun(const T* aString, uint32_t aLength,
                DrawTarget* aRefDrawTarget,
                int32_t aAppUnitsPerDevUnit,
                uint32_t aFlags,
                gfxMissingFontRecorder *aMFR)
    {
        gfxTextRunFactory::Parameters params = {
            aRefDrawTarget, nullptr, nullptr, nullptr, 0, aAppUnitsPerDevUnit
        };
        return MakeTextRun(aString, aLength, &params, aFlags, aMFR);
    }

    /**
     * Get the (possibly-cached) width of the hyphen character.
     * The aCtx and aAppUnitsPerDevUnit parameters will be used only if
     * needed to initialize the cached hyphen width; otherwise they are
     * ignored.
     */
    gfxFloat GetHyphenWidth(gfxTextRun::PropertyProvider* aProvider);

    /**
     * Make a text run representing a single hyphen character.
     * This will use U+2010 HYPHEN if available in the first font,
     * otherwise fall back to U+002D HYPHEN-MINUS.
     * The caller is responsible for deleting the returned text run
     * when no longer required.
     */
    already_AddRefed<gfxTextRun>
    MakeHyphenTextRun(DrawTarget* aDrawTarget, uint32_t aAppUnitsPerDevUnit);

    /**
     * Check whether a given font (specified by its gfxFontEntry)
     * is already in the fontgroup's list of actual fonts
     */
    bool HasFont(const gfxFontEntry *aFontEntry);

    // This returns the preferred underline for this font group.
    // Some CJK fonts have wrong underline offset in its metrics.
    // If this group has such "bad" font, each platform's gfxFontGroup
    // initialized mUnderlineOffset. The value should be lower value of
    // first font's metrics and the bad font's metrics. Otherwise, this
    // returns from first font's metrics.
    enum { UNDERLINE_OFFSET_NOT_SET = INT16_MAX };
    virtual gfxFloat GetUnderlineOffset();

    virtual already_AddRefed<gfxFont>
        FindFontForChar(uint32_t ch, uint32_t prevCh, uint32_t aNextCh,
                        Script aRunScript, gfxFont *aPrevMatchedFont,
                        uint8_t *aMatchType);

    gfxUserFontSet* GetUserFontSet();

    // With downloadable fonts, the composition of the font group can change as fonts are downloaded
    // for each change in state of the user font set, the generation value is bumped to avoid picking up
    // previously created text runs in the text run word cache.  For font groups based on stylesheets
    // with no @font-face rule, this always returns 0.
    uint64_t GetGeneration();

    // generation of the latest fontset rebuild, 0 when no fontset present
    uint64_t GetRebuildGeneration();

    // used when logging text performance
    gfxTextPerfMetrics *GetTextPerfMetrics() { return mTextPerf; }

    // This will call UpdateUserFonts() if the user font set is changed.
    void SetUserFontSet(gfxUserFontSet *aUserFontSet);

    void ClearCachedData()
    {
        mUnderlineOffset = UNDERLINE_OFFSET_NOT_SET;
        mSkipDrawing = false;
        mHyphenWidth = -1;
        mCachedEllipsisTextRun = nullptr;
    }

    // If there is a user font set, check to see whether the font list or any
    // caches need updating.
    virtual void UpdateUserFonts();

    // search for a specific userfont in the list of fonts
    bool ContainsUserFont(const gfxUserFontEntry* aUserFont);

    bool ShouldSkipDrawing() const {
        return mSkipDrawing;
    }

    class LazyReferenceDrawTargetGetter {
    public:
      virtual already_AddRefed<DrawTarget> GetRefDrawTarget() = 0;
    };
    // The gfxFontGroup keeps ownership of this textrun.
    // It is only guaranteed to exist until the next call to GetEllipsisTextRun
    // (which might use a different appUnitsPerDev value or flags) for the font
    // group, or until UpdateUserFonts is called, or the fontgroup is destroyed.
    // Get it/use it/forget it :) - don't keep a reference that might go stale.
    gfxTextRun* GetEllipsisTextRun(int32_t aAppUnitsPerDevPixel, uint32_t aFlags,
                                   LazyReferenceDrawTargetGetter& aRefDrawTargetGetter);

protected:
    // search through pref fonts for a character, return nullptr if no matching pref font
    already_AddRefed<gfxFont> WhichPrefFontSupportsChar(uint32_t aCh,
                                                        uint32_t aNextCh);

    already_AddRefed<gfxFont>
        WhichSystemFontSupportsChar(uint32_t aCh, uint32_t aNextCh,
                                    Script aRunScript);

    template<typename T>
    void ComputeRanges(nsTArray<gfxTextRange>& mRanges,
                       const T *aString, uint32_t aLength,
                       Script aRunScript, uint16_t aOrientation);

    class FamilyFace {
    public:
        FamilyFace() : mFamily(nullptr), mFontEntry(nullptr),
                       mNeedsBold(false), mFontCreated(false),
                       mLoading(false), mInvalid(false),
                       mCheckForFallbackFaces(false)
        { }

        FamilyFace(gfxFontFamily* aFamily, gfxFont* aFont)
            : mFamily(aFamily), mNeedsBold(false), mFontCreated(true),
              mLoading(false), mInvalid(false), mCheckForFallbackFaces(false)
        {
            NS_ASSERTION(aFont, "font pointer must not be null");
            NS_ASSERTION(!aFamily ||
                         aFamily->ContainsFace(aFont->GetFontEntry()),
                         "font is not a member of the given family");
            mFont = aFont;
            NS_ADDREF(aFont);
        }

        FamilyFace(gfxFontFamily* aFamily, gfxFontEntry* aFontEntry,
                   bool aNeedsBold)
            : mFamily(aFamily), mNeedsBold(aNeedsBold), mFontCreated(false),
              mLoading(false), mInvalid(false), mCheckForFallbackFaces(false)
        {
            NS_ASSERTION(aFontEntry, "font entry pointer must not be null");
            NS_ASSERTION(!aFamily ||
                         aFamily->ContainsFace(aFontEntry),
                         "font is not a member of the given family");
            mFontEntry = aFontEntry;
            NS_ADDREF(aFontEntry);
        }

        FamilyFace(const FamilyFace& aOtherFamilyFace)
            : mFamily(aOtherFamilyFace.mFamily),
              mNeedsBold(aOtherFamilyFace.mNeedsBold),
              mFontCreated(aOtherFamilyFace.mFontCreated),
              mLoading(aOtherFamilyFace.mLoading),
              mInvalid(aOtherFamilyFace.mInvalid),
              mCheckForFallbackFaces(aOtherFamilyFace.mCheckForFallbackFaces)
        {
            if (mFontCreated) {
                mFont = aOtherFamilyFace.mFont;
                NS_ADDREF(mFont);
            } else {
                mFontEntry = aOtherFamilyFace.mFontEntry;
                NS_IF_ADDREF(mFontEntry);
            }
        }

        ~FamilyFace()
        {
            if (mFontCreated) {
                NS_RELEASE(mFont);
            } else {
                NS_IF_RELEASE(mFontEntry);
            }
        }

        FamilyFace& operator=(const FamilyFace& aOther)
        {
            if (mFontCreated) {
                NS_RELEASE(mFont);
            } else {
                NS_IF_RELEASE(mFontEntry);
            }

            mFamily = aOther.mFamily;
            mNeedsBold = aOther.mNeedsBold;
            mFontCreated = aOther.mFontCreated;
            mLoading = aOther.mLoading;
            mInvalid = aOther.mInvalid;

            if (mFontCreated) {
                mFont = aOther.mFont;
                NS_ADDREF(mFont);
            } else {
                mFontEntry = aOther.mFontEntry;
                NS_IF_ADDREF(mFontEntry);
            }

            return *this;
        }

        gfxFontFamily* Family() const { return mFamily.get(); }
        gfxFont* Font() const {
            return mFontCreated ? mFont : nullptr;
        }

        gfxFontEntry* FontEntry() const {
            return mFontCreated ? mFont->GetFontEntry() : mFontEntry;
        }

        bool NeedsBold() const { return mNeedsBold; }
        bool IsUserFontContainer() const {
            return FontEntry()->mIsUserFontContainer;
        }
        bool IsLoading() const { return mLoading; }
        bool IsInvalid() const { return mInvalid; }
        void CheckState(bool& aSkipDrawing);
        void SetLoading(bool aIsLoading) { mLoading = aIsLoading; }
        void SetInvalid() { mInvalid = true; }
        bool CheckForFallbackFaces() const { return mCheckForFallbackFaces; }
        void SetCheckForFallbackFaces() { mCheckForFallbackFaces = true; }

        void SetFont(gfxFont* aFont)
        {
            NS_ASSERTION(aFont, "font pointer must not be null");
            NS_ADDREF(aFont);
            if (mFontCreated) {
                NS_RELEASE(mFont);
            } else {
                NS_IF_RELEASE(mFontEntry);
            }
            mFont = aFont;
            mFontCreated = true;
            mLoading = false;
        }

        bool EqualsUserFont(const gfxUserFontEntry* aUserFont) const;

    private:
        RefPtr<gfxFontFamily> mFamily;
        // either a font or a font entry exists
        union {
            gfxFont*            mFont;
            gfxFontEntry*       mFontEntry;
        };
        bool                    mNeedsBold   : 1;
        bool                    mFontCreated : 1;
        bool                    mLoading     : 1;
        bool                    mInvalid     : 1;
        bool                    mCheckForFallbackFaces : 1;
    };

    // List of font families, either named or generic.
    // Generic names map to system pref fonts based on language.
    mozilla::FontFamilyList mFamilyList;

    // Fontlist containing a font entry for each family found. gfxFont objects
    // are created as needed and userfont loads are initiated when needed.
    // Code should be careful about addressing this array directly.
    nsTArray<FamilyFace> mFonts;

    RefPtr<gfxFont> mDefaultFont;
    gfxFontStyle mStyle;

    gfxFloat mUnderlineOffset;
    gfxFloat mHyphenWidth;
    gfxFloat mDevToCssSize;

    RefPtr<gfxUserFontSet> mUserFontSet;
    uint64_t mCurrGeneration;  // track the current user font set generation, rebuild font list if needed

    gfxTextPerfMetrics *mTextPerf;

    // Cache a textrun representing an ellipsis (useful for CSS text-overflow)
    // at a specific appUnitsPerDevPixel size and orientation
    RefPtr<gfxTextRun>   mCachedEllipsisTextRun;

    // cache the most recent pref font to avoid general pref font lookup
    RefPtr<gfxFontFamily> mLastPrefFamily;
    RefPtr<gfxFont>       mLastPrefFont;
    eFontPrefLang           mLastPrefLang;       // lang group for last pref font
    eFontPrefLang           mPageLang;
    bool                    mLastPrefFirstFont;  // is this the first font in the list of pref fonts for this lang group?

    bool                    mSkipDrawing; // hide text while waiting for a font
                                          // download to complete (or fallback
                                          // timer to fire)

    // xxx - gfxPangoFontGroup skips UpdateUserFonts
    bool                    mSkipUpdateUserFonts;

    /**
     * Textrun creation short-cuts for special cases where we don't need to
     * call a font shaper to generate glyphs.
     */
    already_AddRefed<gfxTextRun>
    MakeEmptyTextRun(const Parameters *aParams, uint32_t aFlags);

    already_AddRefed<gfxTextRun>
    MakeSpaceTextRun(const Parameters *aParams, uint32_t aFlags);

    already_AddRefed<gfxTextRun>
    MakeBlankTextRun(uint32_t aLength, const Parameters *aParams,
                     uint32_t aFlags);

    // Initialize the list of fonts
    void BuildFontList();

    // Get the font at index i within the fontlist.
    // Will initiate userfont load if not already loaded.
    // May return null if userfont not loaded or if font invalid
    virtual gfxFont* GetFontAt(int32_t i, uint32_t aCh = 0x20);

    // Whether there's a font loading for a given family in the fontlist
    // for a given character
    bool FontLoadingForFamily(gfxFontFamily* aFamily, uint32_t aCh) const;

    // will always return a font or force a shutdown
    gfxFont* GetDefaultFont();

    // Init this font group's font metrics. If there no bad fonts, you don't need to call this.
    // But if there are one or more bad fonts which have bad underline offset,
    // you should call this with the *first* bad font.
    void InitMetricsForBadFont(gfxFont* aBadFont);

    // Set up the textrun glyphs for an entire text run:
    // find script runs, and then call InitScriptRun for each
    template<typename T>
    void InitTextRun(DrawTarget* aDrawTarget,
                     gfxTextRun *aTextRun,
                     const T *aString,
                     uint32_t aLength,
                     gfxMissingFontRecorder *aMFR);

    // InitTextRun helper to handle a single script run, by finding font ranges
    // and calling each font's InitTextRun() as appropriate
    template<typename T>
    void InitScriptRun(DrawTarget* aDrawTarget,
                       gfxTextRun *aTextRun,
                       const T *aString,
                       uint32_t aScriptRunStart,
                       uint32_t aScriptRunEnd,
                       Script aRunScript,
                       gfxMissingFontRecorder *aMFR);

    // Helper for font-matching:
    // search all faces in a family for a fallback in cases where it's unclear
    // whether the family might have a font for a given character
    already_AddRefed<gfxFont>
    FindFallbackFaceForChar(gfxFontFamily* aFamily, uint32_t aCh,
                            Script aRunScript);

   // helper methods for looking up fonts

    // lookup and add a font with a given name (i.e. *not* a generic!)
    void AddPlatformFont(const nsAString& aName,
                         nsTArray<gfxFontFamily*>& aFamilyList);

    // do style selection and add entries to list
    void AddFamilyToFontList(gfxFontFamily* aFamily);

    static nsILanguageAtomService* gLangService;
};

// A "missing font recorder" is to be used during text-run creation to keep
// a record of any scripts encountered for which font coverage was lacking;
// when Flush() is called, it sends a notification that front-end code can use
// to download fonts on demand (or whatever else it wants to do).

#define GFX_MISSING_FONTS_NOTIFY_PREF "gfx.missing_fonts.notify"

class gfxMissingFontRecorder {
public:
    gfxMissingFontRecorder()
    {
        MOZ_COUNT_CTOR(gfxMissingFontRecorder);
        memset(&mMissingFonts, 0, sizeof(mMissingFonts));
    }

    ~gfxMissingFontRecorder()
    {
#ifdef DEBUG
        for (uint32_t i = 0; i < kNumScriptBitsWords; i++) {
            NS_ASSERTION(mMissingFonts[i] == 0,
                         "failed to flush the missing-font recorder");
        }
#endif
        MOZ_COUNT_DTOR(gfxMissingFontRecorder);
    }

    // record this script code in our mMissingFonts bitset
    void RecordScript(mozilla::unicode::Script aScriptCode)
    {
        mMissingFonts[static_cast<uint32_t>(aScriptCode) >> 5] |=
            (1 << (static_cast<uint32_t>(aScriptCode) & 0x1f));
    }

    // send a notification of any missing-scripts that have been
    // recorded, and clear the mMissingFonts set for re-use
    void Flush();

    // forget any missing-scripts that have been recorded up to now;
    // called before discarding a recorder we no longer care about
    void Clear()
    {
        memset(&mMissingFonts, 0, sizeof(mMissingFonts));
    }

private:
    // Number of 32-bit words needed for the missing-script flags
    static const uint32_t kNumScriptBitsWords =
        ((static_cast<int>(mozilla::unicode::Script::NUM_SCRIPT_CODES) + 31) / 32);
    uint32_t mMissingFonts[kNumScriptBitsWords];
};

#endif