1 files changed, 153 insertions, 0 deletions
diff --git a/gfx/thebes/gfxGlyphExtents.h b/gfx/thebes/gfxGlyphExtents.h
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+++ b/gfx/thebes/gfxGlyphExtents.h
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+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * 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 "gfxRect.h"
+#include "nsTHashtable.h"
+#include "nsHashKeys.h"
+#include "nsTArray.h"
+#include "mozilla/MemoryReporting.h"
+
+class gfxContext;
+
+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), x(0.0), y(0.0), width(0.0), height(0.0) {}
+    HashEntry(HashEntry&& aOther)
+        : nsUint32HashKey(std::move(aOther)),
+          x(aOther.x),
+          y(aOther.y),
+          width(aOther.width),
+          height(aOther.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