1 files changed, 151 insertions, 0 deletions
diff --git a/gfx/thebes/gfxGlyphExtents.h b/gfx/thebes/gfxGlyphExtents.h
new file mode 100644
index 000000000..7da6d9192
--- /dev/null
+++ b/gfx/thebes/gfxGlyphExtents.h
@@ -0,0 +1,151 @@
+/* -*- Mode: C++; tab-width: 20; 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_GLYPHEXTENTS_H
+#define GFX_GLYPHEXTENTS_H
+
+#include "gfxFont.h"
+#include "nsTHashtable.h"
+#include "nsHashKeys.h"
+#include "nsTArray.h"
+#include "mozilla/MemoryReporting.h"
+
+class gfxContext;
+struct gfxRect;
+
+namespace mozilla {
+namespace gfx {
+class DrawTarget;
+} // namespace gfx
+} // namespace mozilla
+
+/**
+ * This stores glyph bounds information for a particular gfxFont, at
+ * a particular appunits-per-dev-pixel ratio (because the compressed glyph
+ * width array is stored in appunits).
+ * 
+ * We store a hashtable from glyph IDs to float bounding rects. For the
+ * common case where the glyph has no horizontal left bearing, and no
+ * y overflow above the font ascent or below the font descent, and tight
+ * bounding boxes are not required, we avoid storing the glyph ID in the hashtable
+ * and instead consult an array of 16-bit glyph XMost values (in appunits).
+ * This array always has an entry for the font's space glyph --- the width is
+ * assumed to be zero.
+ */
+class gfxGlyphExtents {
+    typedef mozilla::gfx::DrawTarget DrawTarget;
+
+public:
+    explicit gfxGlyphExtents(int32_t aAppUnitsPerDevUnit) :
+        mAppUnitsPerDevUnit(aAppUnitsPerDevUnit) {
+        MOZ_COUNT_CTOR(gfxGlyphExtents);
+    }
+    ~gfxGlyphExtents();
+
+    enum { INVALID_WIDTH = 0xFFFF };
+
+    void NotifyGlyphsChanged() {
+        mTightGlyphExtents.Clear();
+    }
+
+    // returns INVALID_WIDTH => not a contained glyph
+    // Otherwise the glyph has no before-bearing or vertical bearings,
+    // and the result is its width measured from the baseline origin, in
+    // appunits.
+    uint16_t GetContainedGlyphWidthAppUnits(uint32_t aGlyphID) const {
+        return mContainedGlyphWidths.Get(aGlyphID);
+    }
+
+    bool IsGlyphKnown(uint32_t aGlyphID) const {
+        return mContainedGlyphWidths.Get(aGlyphID) != INVALID_WIDTH ||
+            mTightGlyphExtents.GetEntry(aGlyphID) != nullptr;
+    }
+
+    bool IsGlyphKnownWithTightExtents(uint32_t aGlyphID) const {
+        return mTightGlyphExtents.GetEntry(aGlyphID) != nullptr;
+    }
+
+    // Get glyph extents; a rectangle relative to the left baseline origin
+    // Returns true on success. Can fail on OOM or when aContext is null
+    // and extents were not (successfully) prefetched.
+    bool GetTightGlyphExtentsAppUnits(gfxFont* aFont,
+            DrawTarget* aDrawTarget, uint32_t aGlyphID, gfxRect* aExtents);
+
+    void SetContainedGlyphWidthAppUnits(uint32_t aGlyphID, uint16_t aWidth) {
+        mContainedGlyphWidths.Set(aGlyphID, aWidth);
+    }
+    void SetTightGlyphExtents(uint32_t aGlyphID, const gfxRect& aExtentsAppUnits);
+
+    int32_t GetAppUnitsPerDevUnit() { return mAppUnitsPerDevUnit; }
+
+    size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
+    size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
+
+private:
+    class HashEntry : public nsUint32HashKey {
+    public:
+        // When constructing a new entry in the hashtable, we'll leave this
+        // blank. The caller of Put() will fill this in.
+        explicit HashEntry(KeyTypePointer aPtr) : nsUint32HashKey(aPtr) {}
+        HashEntry(const HashEntry& toCopy) : nsUint32HashKey(toCopy) {
+          x = toCopy.x; y = toCopy.y; width = toCopy.width; height = toCopy.height;
+        }
+
+        float x, y, width, height;
+    };
+
+    enum { BLOCK_SIZE_BITS = 7, BLOCK_SIZE = 1 << BLOCK_SIZE_BITS }; // 128-glyph blocks
+
+    class GlyphWidths {
+    public:
+        void Set(uint32_t aIndex, uint16_t aValue);
+        uint16_t Get(uint32_t aIndex) const {
+            uint32_t block = aIndex >> BLOCK_SIZE_BITS;
+            if (block >= mBlocks.Length())
+                return INVALID_WIDTH;
+            uintptr_t bits = mBlocks[block];
+            if (!bits)
+                return INVALID_WIDTH;
+            uint32_t indexInBlock = aIndex & (BLOCK_SIZE - 1);
+            if (bits & 0x1) {
+                if (GetGlyphOffset(bits) != indexInBlock)
+                    return INVALID_WIDTH;
+                return GetWidth(bits);
+            }
+            uint16_t *widths = reinterpret_cast<uint16_t *>(bits);
+            return widths[indexInBlock];
+        }
+
+        uint32_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
+        
+        ~GlyphWidths();
+
+    private:
+        static uint32_t GetGlyphOffset(uintptr_t aBits) {
+            NS_ASSERTION(aBits & 0x1, "This is really a pointer...");
+            return (aBits >> 1) & ((1 << BLOCK_SIZE_BITS) - 1);
+        }
+        static uint32_t GetWidth(uintptr_t aBits) {
+            NS_ASSERTION(aBits & 0x1, "This is really a pointer...");
+            return aBits >> (1 + BLOCK_SIZE_BITS);
+        }
+        static uintptr_t MakeSingle(uint32_t aGlyphOffset, uint16_t aWidth) {
+            return (aWidth << (1 + BLOCK_SIZE_BITS)) + (aGlyphOffset << 1) + 1;
+        }
+
+        nsTArray<uintptr_t> mBlocks;
+    };
+
+    GlyphWidths             mContainedGlyphWidths;
+    nsTHashtable<HashEntry> mTightGlyphExtents;
+    int32_t                 mAppUnitsPerDevUnit;
+
+private:
+    // not implemented:
+    gfxGlyphExtents(const gfxGlyphExtents& aOther) = delete;
+    gfxGlyphExtents& operator=(const gfxGlyphExtents& aOther) = delete;
+};
+
+#endif