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Unified Diff: Source/core/platform/graphics/ImageSource.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/graphics/ImageSource.h
diff --git a/Source/core/platform/graphics/ImageSource.h b/Source/core/platform/graphics/ImageSource.h
index 084b3fa9cc58b056ef5bcbcb9b983097a1111f69..e9fc415ba791fbe44b10be833f3adb8250a68cce 100644
--- a/Source/core/platform/graphics/ImageSource.h
+++ b/Source/core/platform/graphics/ImageSource.h
@@ -80,30 +80,24 @@ public:
~ImageSource();
// Tells the ImageSource that the Image no longer cares about decoded frame
- // data -- at all (if |destroyAll| is true), or before frame
- // |clearBeforeFrame| (if |destroyAll| is false). The ImageSource should
- // delete cached decoded data for these frames where possible to keep memory
- // usage low. When |destroyAll| is true, the ImageSource should also reset
- // any local state so that decoding can begin again.
+ // data except for the specified frame. Callers may pass WTF::notFound to
+ // clear all frames.
//
- // Implementations that delete less than what's specified above waste
- // memory. Implementations that delete more may burn CPU re-decoding frames
- // that could otherwise have been cached, or encounter errors if they're
- // asked to decode frames they can't decode due to the loss of previous
- // decoded frames.
+ // In response, the ImageSource should delete cached decoded data for other
+ // frames where possible to keep memory use low. The expectation is that in
+ // the future, the caller may call createFrameAtIndex() with an index larger
+ // than the one passed to this function, and the implementation may then
+ // make use of the preserved frame data here in decoding that frame.
+ // By contrast, callers who call this function and then later ask for an
+ // earlier frame may require more work to be done, e.g. redecoding the image
+ // from the beginning.
//
- // Callers should not call clear(false, n) and subsequently call
- // createFrameAtIndex(m) with m < n, unless they first call clear(true).
- // This ensures that stateful ImageSources/decoders will work properly.
+ // Implementations may elect to preserve more frames than the one requested
+ // here if doing so is likely to save CPU time in the future, but will pay
+ // an increased memory cost to do so.
//
- // The |data| and |allDataReceived| parameters should be supplied by callers
- // who set |destroyAll| to true if they wish to be able to continue using
- // the ImageSource. This way implementations which choose to destroy their
- // decoders in some cases can reconstruct them correctly.
- void clear(bool destroyAll,
- size_t clearBeforeFrame = 0,
- SharedBuffer* data = NULL,
- bool allDataReceived = false);
+ // Returns the number of bytes of frame data actually cleared.
+ size_t clearCacheExceptFrame(size_t);
bool initialized() const;
@@ -122,8 +116,6 @@ public:
size_t frameCount() const;
- // Callers should not call this after calling clear() with a higher index;
- // see comments on clear() above.
PassNativeImagePtr createFrameAtIndex(size_t);
float frameDurationAtIndex(size_t) const;
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