WIP: Implement APNG

third_party/WebKit/Source/platform/image-decoders/png/PNGImageDecoder.h

Index: third_party/WebKit/Source/platform/image-decoders/png/PNGImageDecoder.h
diff --git a/third_party/WebKit/Source/platform/image-decoders/png/PNGImageDecoder.h b/third_party/WebKit/Source/platform/image-decoders/png/PNGImageDecoder.h
index 7ce6aa0faf83c7c6d2ece1ce6cc94ea5d07f7427..8ebdca5537dcb8992141b6e063e1a7314d91e144 100644
--- a/third_party/WebKit/Source/platform/image-decoders/png/PNGImageDecoder.h
+++ b/third_party/WebKit/Source/platform/image-decoders/png/PNGImageDecoder.h
@@ -43,26 +43,52 @@ class PLATFORM_EXPORT PNGImageDecoder final : public ImageDecoder {
                   size_t offset = 0);
   ~PNGImageDecoder() override;
 
+  enum class PNGParseQuery { PNGSizeQuery, PNGMetaDataQuery };
+
   // ImageDecoder:
   String filenameExtension() const override { return "png"; }
+  int repetitionCount() const override;
+  bool frameIsCompleteAtIndex(size_t) const override;
+  float frameDurationAtIndex(size_t) const override;
+  size_t clearCacheExceptFrame(size_t) override;
 
   // Callbacks from libpng
   void headerAvailable();
   void rowAvailable(unsigned char* row, unsigned rowIndex, int);
   void complete();
 
+  // Additional methods used for APNG
+  void setRepetitionCount(size_t);
+
  private:
   // ImageDecoder:
-  void decodeSize() override { decode(true); }
-  void decode(size_t) override { decode(false); }
+  void decodeSize() override { parse(PNGParseQuery::PNGSizeQuery); }
+  void decode(size_t) override;
+  size_t decodeFrameCount() override;
+  void initializeNewFrame(size_t) override;
+  void clearFrameBuffer(size_t) override;
 
-  // Decodes the image.  If |onlySize| is true, stops decoding after
-  // calculating the image size.  If decoding fails but there is no more
-  // data coming, sets the "decode failure" flag.
-  void decode(bool onlySize);
+  bool initFrameBuffer(size_t);
+  void parse(PNGParseQuery);
+  // Used by clearCacheExceptFrame if two frames need to be kept in cache.
+  size_t clearCacheExceptTwoFrames(size_t, size_t);
+  // Non-first frames that depend on previous frames should not be decoded row

[scroggo_chromium, 2016/11/09 13:42:50]

I don't think "Non-first" is necessary here. The first frame cannot depend on a
previous frame, so "that depend on previous frames" makes it clear you're not
talking about the first one.

[joostouwerling, 2016/11/11 20:22:19]

Acknowledged.

+  // by row, to prevent partially overwriting the content of the previous frame.
+  // The frame at |index| must exist before calling this method.
+  bool frameShouldBeDecodedIncrementally(size_t index) {
+    ASSERT(index < m_frameBufferCache.size());
+    return (index == 0 ||
+           m_frameBufferCache[index].requiredPreviousFrameIndex() == kNotFound);
+  }
 
   std::unique_ptr<PNGImageReader> m_reader;
   const unsigned m_offset;
+  size_t m_frameCount;
+  size_t m_currentFrame;
+  // m_repetitionCount is set to cAnimationLoopOnce by default, so the
+  // DeferredImageDecoder takes into account that this may be an animated
+  // image, but we don't know for sure yet.
+  int m_repetitionCount;
 };
 
 }  // namespace blink