Move gif image decoder to SkCodec

third_party/WebKit/Source/platform/image-decoders/gif/GIFImageDecoder.h

Index: third_party/WebKit/Source/platform/image-decoders/gif/GIFImageDecoder.h
diff --git a/third_party/WebKit/Source/platform/image-decoders/gif/GIFImageDecoder.h b/third_party/WebKit/Source/platform/image-decoders/gif/GIFImageDecoder.h
index dec862c04dd80bc31c93bb790634b522496d3a4c..17582d5002559b4681f461094bd5e2e7b0788fab 100644
--- a/third_party/WebKit/Source/platform/image-decoders/gif/GIFImageDecoder.h
+++ b/third_party/WebKit/Source/platform/image-decoders/gif/GIFImageDecoder.h
@@ -28,72 +28,52 @@
 
 #include <memory>
 #include "platform/image-decoders/ImageDecoder.h"
+#include "platform/image-decoders/SegmentStream.h"
 #include "platform/wtf/Noncopyable.h"
+#include "platform/wtf/RefPtr.h"
+#include "third_party/skia/include/codec/SkCodec.h"
 
 namespace blink {
 
-class GIFImageReader;
-
-using GIFRow = Vector<unsigned char>;
-
 // This class decodes the GIF image format.
-class PLATFORM_EXPORT GIFImageDecoder final : public ImageDecoder {
+class PLATFORM_EXPORT GIFImageDecoder final : public blink::ImageDecoder {
   WTF_MAKE_NONCOPYABLE(GIFImageDecoder);
 
  public:
   GIFImageDecoder(AlphaOption, const ColorBehavior&, size_t max_decoded_bytes);
   ~GIFImageDecoder() override;
 
-  enum GIFParseQuery { kGIFSizeQuery, kGIFFrameCountQuery };
-
   // ImageDecoder:
   String FilenameExtension() const override { return "gif"; }
   void OnSetData(SegmentReader* data) override;
   int RepetitionCount() const override;
   bool FrameIsCompleteAtIndex(size_t) const override;
   float FrameDurationAtIndex(size_t) const override;
-  // CAUTION: SetFailed() deletes |reader_|.  Be careful to avoid
-  // accessing deleted memory, especially when calling this from inside
-  // GIFImageReader!
+  // CAUTION: SetFailed() deletes |codec_|. Be careful to avoid
+  // accessing deleted memory.
   bool SetFailed() override;
 
-  // Callbacks from the GIF reader.
-  bool HaveDecodedRow(size_t frame_index,
-                      GIFRow::const_iterator row_begin,
-                      size_t width,
-                      size_t row_number,
-                      unsigned repeat_count,
-                      bool write_transparent_pixels);
-  bool FrameComplete(size_t frame_index);
-
-  // For testing.
-  bool ParseCompleted() const;
+  size_t ClearCacheExceptFrame(size_t) override;
 
  private:
   // ImageDecoder:
-  void ClearFrameBuffer(size_t frame_index) override;
-  virtual void DecodeSize() { Parse(kGIFSizeQuery); }
+  void DecodeSize() override {}
   size_t DecodeFrameCount() override;
-  void InitializeNewFrame(size_t) override;
-  void Decode(size_t) override;
-
-  // Parses as much as is needed to answer the query, ignoring bitmap
-  // data. If parsing fails, sets the "decode failure" flag.
-  void Parse(GIFParseQuery);
-
-  // Reset the alpha tracker for this frame. Before calling this method, the
-  // caller must verify that the frame exists.
-  void OnInitFrameBuffer(size_t) override;
-
+  void InitializeNewFrame(size_t index) override;
+  void Decode(size_t index) override;
   // When the disposal method of the frame is DisposeOverWritePrevious, the
-  // next frame will use the previous frame's buffer as its starting state, so
+  // next frame will use a previous frame's buffer as its starting state, so
   // we can't take over the data in that case. Before calling this method, the
   // caller must verify that the frame exists.
   bool CanReusePreviousFrameBuffer(size_t) const override;
 
-  bool current_buffer_saw_alpha_;
-  mutable int repetition_count_;
-  std::unique_ptr<GIFImageReader> reader_;
+  size_t GetPreviousReferenceFrame(size_t index) const;

[scroggo_chromium, 2017/07/17 20:07:56]

Add a comment, describing what this does?

The particular interesting bit is that it returns a reference frame that is
FrameComplete. (Maybe there's a concise way to work that into the name
somehow... GetViableStartingFrame?)

[vmpstr, 2017/07/17 21:28:41]

I think a comment is definitely the way to go here (even with a different
function name)

[cblume, 2017/07/18 10:23:49]

Done.

The comment (and new name) I think better describe why the function exists and
what it does. I think it does this succinctly.

There is also a comment in the implementation explaining it in greater detail.

+
+  std::unique_ptr<SkCodec> codec_;
+  // segment_stream_ is a raw pointer because it passes ownership to

[vmpstr, 2017/07/17 21:28:41]

Maybe just: |codec_| owns the SegmentStream, but we need a reference to it to
append more data as it arrives. 

[cblume, 2017/07/18 10:23:49]

Done.

[scroggo_chromium, 2017/07/18 17:52:42]

I think Chris originally used the word "reference", but I discouraged it because
it sounded like it was reference counted, and it is not.

[cblume, 2017/07/19 23:27:04]

Done.
I changed vmpstr@'s suggested comment to say "...but we need access to it..." to
remove the word "reference".

+  // codec_ when codec_ is created. However, we still need the
+  // pointer so we can append more data as it arrives.
+  SegmentStream* segment_stream_;
 };
 
 }  // namespace blink