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Unified Diff: Source/core/platform/image-decoders/ImageDecoder.h

Issue 15350006: Decode GIF image frames on demand. (Closed) Base URL: https://chromium.googlesource.com/chromium/blink.git@master
Patch Set: Rebased Created 7 years, 7 months ago
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Index: Source/core/platform/image-decoders/ImageDecoder.h
diff --git a/Source/core/platform/image-decoders/ImageDecoder.h b/Source/core/platform/image-decoders/ImageDecoder.h
index 724e27c918dc3e3c7a5dcd00f2ef98bfa3cd2aeb..591548dc1b66be8314bbdbc14affef93a64acc24 100644
--- a/Source/core/platform/image-decoders/ImageDecoder.h
+++ b/Source/core/platform/image-decoders/ImageDecoder.h
@@ -115,6 +115,14 @@ namespace WebCore {
FrameDisposalMethod disposalMethod() const { return m_disposalMethod; }
bool premultiplyAlpha() const { return m_premultiplyAlpha; }
void reportMemoryUsage(MemoryObjectInfo*) const;
+ size_t requiredPreviousFrameIndex() const
+ {
+ ASSERT(m_requiredPreviousFrameIndexValid);
+ return m_requiredPreviousFrameIndex;
+ }
+#if !ASSERT_DISABLED
+ bool requiredPreviousFrameIndexValid() const { return m_requiredPreviousFrameIndexValid; }
+#endif
void setHasAlpha(bool alpha);
void setOriginalFrameRect(const IntRect& r) { m_originalFrameRect = r; }
@@ -122,6 +130,13 @@ namespace WebCore {
void setDuration(unsigned duration) { m_duration = duration; }
void setDisposalMethod(FrameDisposalMethod method) { m_disposalMethod = method; }
void setPremultiplyAlpha(bool premultiplyAlpha) { m_premultiplyAlpha = premultiplyAlpha; }
+ void setRequiredPreviousFrameIndex(size_t previousFrameIndex)
+ {
+ m_requiredPreviousFrameIndex = previousFrameIndex;
+#if !ASSERT_DISABLED
+ m_requiredPreviousFrameIndexValid = true;
+#endif
+ }
inline void setRGBA(int x, int y, unsigned r, unsigned g, unsigned b, unsigned a)
{
@@ -200,6 +215,15 @@ namespace WebCore {
unsigned m_duration;
FrameDisposalMethod m_disposalMethod;
bool m_premultiplyAlpha;
+
+ // The frame that must be decoded before this frame can be decoded.
+ // WTF::notFound if this frame doesn't require any previous frame.
+ // This is used by ImageDecoder::clearCacheExceptFrame(), and will never
+ // be read for image formats that do not have multiple frames.
+ size_t m_requiredPreviousFrameIndex;
+#if !ASSERT_DISABLED
+ bool m_requiredPreviousFrameIndexValid;
+#endif
};
// ImageDecoder is a base for all format-specific decoders
@@ -358,10 +382,13 @@ namespace WebCore {
bool failed() const { return m_failed; }
- // Clears decoded pixel data from before the provided frame unless that
- // data may be needed to decode future frames (e.g. due to GIF frame
- // compositing).
- virtual void clearFrameBufferCache(size_t) { }
+ // Clears decoded pixel data from all frames except the provided frame,
+ // unless that frame has status FrameEmpty, in which case we instead
+ // preserve the most recent frame whose data is required in order to
+ // decode this frame. Callers may pass WTF::notFound to clear all frames.
+ //
+ // Returns the number of bytes of frame data actually cleared.
+ size_t clearCacheExceptFrame(size_t);
// If the image has a cursor hot-spot, stores it in the argument
// and returns true. Otherwise returns false.
@@ -378,6 +405,25 @@ namespace WebCore {
}
protected:
+ // Calculates the most recent frame whose image data may be needed in
+ // order to decode frame |frameIndex|, based on frame disposal methods.
+ // If no previous frame's data is required, returns WTF::notFound.
+ //
+ // This function requires that the previous frame's
+ // |m_requiredPreviousFrameIndex| member has been set correctly. The
+ // easiest way to ensure this is for subclasses to call this method and
+ // store the result on the frame via setRequiredPreviousFrameIndex()
+ // as soon as the frame has been created and parsed sufficiently to
+ // determine the disposal method; assuming this happens for all frames
+ // in order, the required invariant will hold.
+ //
+ // Image formats which do not use more than one frame do not need to
+ // worry about this; see comments on
+ // ImageFrame::m_requiredPreviousFrameIndex.
+ size_t findRequiredPreviousFrame(size_t frameIndex);
+
+ virtual void clearFrameBuffer(size_t frameIndex);
+
RefPtr<SharedBuffer> m_data; // The encoded data.
Vector<ImageFrame, 1> m_frameBufferCache;
bool m_premultiplyAlpha;
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