tor-browser

gfxGlyphExtents.h (5995B)

---

/* -*- 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"
#include "mozilla/RWLock.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),
       mLock("gfxGlyphExtents lock") {
   MOZ_COUNT_CTOR(gfxGlyphExtents);
 }
 ~gfxGlyphExtents();

 enum { INVALID_WIDTH = 0xFFFF };

 void NotifyGlyphsChanged() {
   mozilla::AutoWriteLock lock(mLock);
   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 GetContainedGlyphWidthAppUnitsLocked(uint32_t aGlyphID) const
     MOZ_REQUIRES_SHARED(mLock) {
   return mContainedGlyphWidths.Get(aGlyphID);
 }

 bool IsGlyphKnownLocked(uint32_t aGlyphID) const MOZ_REQUIRES_SHARED(mLock) {
   return mContainedGlyphWidths.Get(aGlyphID) != INVALID_WIDTH ||
          mTightGlyphExtents.GetEntry(aGlyphID) != nullptr;
 }

 bool IsGlyphKnownWithTightExtentsLocked(uint32_t aGlyphID) const
     MOZ_REQUIRES_SHARED(mLock) {
   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 GetTightGlyphExtentsAppUnitsLocked(gfxFont* aFont,
                                         DrawTarget* aDrawTarget,
                                         uint32_t aGlyphID, gfxRect* aExtents)
     MOZ_REQUIRES_SHARED(mLock);
 bool GetTightGlyphExtentsAppUnits(gfxFont* aFont, DrawTarget* aDrawTarget,
                                   uint32_t aGlyphID, gfxRect* aExtents) {
   mozilla::AutoReadLock lock(mLock);
   return GetTightGlyphExtentsAppUnitsLocked(aFont, aDrawTarget, aGlyphID,
                                             aExtents);
 }

 void SetContainedGlyphWidthAppUnits(uint32_t aGlyphID, uint16_t aWidth) {
   mozilla::AutoWriteLock lock(mLock);
   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 MOZ_GUARDED_BY(mLock);
 nsTHashtable<HashEntry> mTightGlyphExtents MOZ_GUARDED_BY(mLock);
 const int32_t mAppUnitsPerDevUnit;

public:
 mutable mozilla::RWLock mLock;

private:
 // not implemented:
 gfxGlyphExtents(const gfxGlyphExtents& aOther) = delete;
 gfxGlyphExtents& operator=(const gfxGlyphExtents& aOther) = delete;
};

#endif