Bug 1777475 - Add locking to the gfxGlyphExtents class. r=lsalzman

Differential Revision: https://phabricator.services.mozilla.com/D150750

gfx/thebes/gfxGlyphExtents.cpp

@@ -37,6 +37,7 @@ bool gfxGlyphExtents::GetTightGlyphExtentsAppUnits(gfxFont* aFont,
                                                    DrawTarget* aDrawTarget,
                                                    uint32_t aGlyphID,
                                                    gfxRect* aExtents) {
+  AutoReadLock lock(mLock);
   HashEntry* entry = mTightGlyphExtents.GetEntry(aGlyphID);
   if (!entry) {
     // Some functions higher up in the call chain deliberately pass in a
@@ -50,7 +51,11 @@ bool gfxGlyphExtents::GetTightGlyphExtentsAppUnits(gfxFont* aFont,
 #ifdef DEBUG_TEXT_RUN_STORAGE_METRICS
     ++gGlyphExtentsSetupLazyTight;
 #endif
+    // We need to temporarily release the read lock, as SetupGlyphExtents will
+    // take a write lock internally when it wants to set the new entry.
+    mLock.ReadUnlock();
     aFont->SetupGlyphExtents(aDrawTarget, aGlyphID, true, this);
+    mLock.ReadLock();
     entry = mTightGlyphExtents.GetEntry(aGlyphID);
     if (!entry) {
       NS_WARNING("Could not get glyph extents");
@@ -122,8 +127,11 @@ void gfxGlyphExtents::GlyphWidths::Set(uint32_t aGlyphID, uint16_t aWidth) {
 
 void gfxGlyphExtents::SetTightGlyphExtents(uint32_t aGlyphID,
                                            const gfxRect& aExtentsAppUnits) {
+  AutoWriteLock lock(mLock);
   HashEntry* entry = mTightGlyphExtents.PutEntry(aGlyphID);
-  if (!entry) return;
+  if (!entry) {
+    return;
+  }
   entry->x = aExtentsAppUnits.X();
   entry->y = aExtentsAppUnits.Y();
   entry->width = aExtentsAppUnits.Width();
@@ -131,6 +139,7 @@ void gfxGlyphExtents::SetTightGlyphExtents(uint32_t aGlyphID,
 }
 
 size_t gfxGlyphExtents::SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const {
+  AutoReadLock lock(mLock);
   return mContainedGlyphWidths.SizeOfExcludingThis(aMallocSizeOf) +
          mTightGlyphExtents.ShallowSizeOfExcludingThis(aMallocSizeOf);
 }

gfx/thebes/gfxGlyphExtents.h

@@ -12,6 +12,7 @@
 #include "nsHashKeys.h"
 #include "nsTArray.h"
 #include "mozilla/MemoryReporting.h"
+#include "mozilla/RWLock.h"
 
 class gfxContext;
 
@@ -39,29 +40,36 @@ class gfxGlyphExtents {
 
  public:
   explicit gfxGlyphExtents(int32_t aAppUnitsPerDevUnit)
-      : mAppUnitsPerDevUnit(aAppUnitsPerDevUnit) {
+      : mAppUnitsPerDevUnit(aAppUnitsPerDevUnit),
+        mLock("gfxGlyphExtents lock") {
     MOZ_COUNT_CTOR(gfxGlyphExtents);
   }
   ~gfxGlyphExtents();
 
   enum { INVALID_WIDTH = 0xFFFF };
 
-  void NotifyGlyphsChanged() { mTightGlyphExtents.Clear(); }
+  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 GetContainedGlyphWidthAppUnits(uint32_t aGlyphID) const {
+    mozilla::AutoReadLock lock(mLock);
     return mContainedGlyphWidths.Get(aGlyphID);
   }
 
   bool IsGlyphKnown(uint32_t aGlyphID) const {
+    mozilla::AutoReadLock lock(mLock);
     return mContainedGlyphWidths.Get(aGlyphID) != INVALID_WIDTH ||
            mTightGlyphExtents.GetEntry(aGlyphID) != nullptr;
   }
 
   bool IsGlyphKnownWithTightExtents(uint32_t aGlyphID) const {
+    mozilla::AutoReadLock lock(mLock);
     return mTightGlyphExtents.GetEntry(aGlyphID) != nullptr;
   }
 
@@ -72,6 +80,7 @@ class gfxGlyphExtents {
                                     uint32_t aGlyphID, gfxRect* 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);
@@ -140,9 +149,10 @@ class gfxGlyphExtents {
     nsTArray<uintptr_t> mBlocks;
   };
 
-  GlyphWidths mContainedGlyphWidths;
-  nsTHashtable<HashEntry> mTightGlyphExtents;
-  int32_t mAppUnitsPerDevUnit;
+  GlyphWidths mContainedGlyphWidths GUARDED_BY(mLock);
+  nsTHashtable<HashEntry> mTightGlyphExtents GUARDED_BY(mLock);
+  const int32_t mAppUnitsPerDevUnit;
+  mutable mozilla::RWLock mLock;
 
  private:
   // not implemented: