Bug 928806 - Allow SharedPlanarYCbCrImage images to optionally have padding

Overload YCbCrImageDataSerializer.InitializeBufferInfo to take explicit plane
offsets. Make SharedPlanarYCbCrImage::SetDataNoCopy set the offsets based on the
Y, Cb and Cr plane pointers passed by the caller. r=nical

gfx/layers/YCbCrImageDataSerializer.cpp

@@ -153,17 +153,18 @@ YCbCrImageDataSerializer::ComputeMinBufferSize(uint32_t aSize)
 }
 
 void
-YCbCrImageDataSerializer::InitializeBufferInfo(const gfx::IntSize& aYSize,
+YCbCrImageDataSerializer::InitializeBufferInfo(uint32_t aYOffset,
+                                               uint32_t aCbOffset,
+                                               uint32_t aCrOffset,
+                                               const gfx::IntSize& aYSize,
                                                const gfx::IntSize& aCbCrSize,
                                                StereoMode aStereoMode)
 {
   YCbCrBufferInfo* info = GetYCbCrBufferInfo(mData);
-  info->mYOffset = MOZ_ALIGN_WORD(sizeof(YCbCrBufferInfo));
-  info->mCbOffset = info->mYOffset
-                  + MOZ_ALIGN_WORD(aYSize.width * aYSize.height);
-  info->mCrOffset = info->mCbOffset
-                  + MOZ_ALIGN_WORD(aCbCrSize.width * aCbCrSize.height);
-
+  uint32_t info_size = MOZ_ALIGN_WORD(sizeof(YCbCrBufferInfo));
+  info->mYOffset = info_size + aYOffset;
+  info->mCbOffset = info_size + aCbOffset;
+  info->mCrOffset = info_size + aCrOffset;
   info->mYWidth = aYSize.width;
   info->mYHeight = aYSize.height;
   info->mCbCrWidth = aCbCrSize.width;
@@ -171,6 +172,17 @@ YCbCrImageDataSerializer::InitializeBufferInfo(const gfx::IntSize& aYSize,
   info->mStereoMode = aStereoMode;
 }
 
+void
+YCbCrImageDataSerializer::InitializeBufferInfo(const gfx::IntSize& aYSize,
+                                               const gfx::IntSize& aCbCrSize,
+                                               StereoMode aStereoMode)
+{
+  uint32_t yOffset = 0;
+  uint32_t cbOffset = yOffset + MOZ_ALIGN_WORD(aYSize.width * aYSize.height);
+  uint32_t crOffset = cbOffset + MOZ_ALIGN_WORD(aCbCrSize.width * aCbCrSize.height);
+  return InitializeBufferInfo(yOffset, cbOffset, crOffset, aYSize, aCbCrSize, aStereoMode);
+}
+
 void
 YCbCrImageDataSerializer::InitializeBufferInfo(const gfxIntSize& aYSize,
                                                const gfxIntSize& aCbCrSize,

gfx/layers/YCbCrImageDataSerializer.h

@@ -114,6 +114,12 @@ public:
    * The provided pointer should point to the beginning of the (chunk of)
    * buffer on which we want to store the image.
    */
+  void InitializeBufferInfo(uint32_t aYOffset,
+                            uint32_t aCbOffset,
+                            uint32_t aCrOffset,
+                            const gfx::IntSize& aYSize,
+                            const gfx::IntSize& aCbCrSize,
+                            StereoMode aStereoMode);
   void InitializeBufferInfo(const gfx::IntSize& aYSize,
                             const gfx::IntSize& aCbCrSize,
                             StereoMode aStereoMode);

gfx/layers/ipc/SharedPlanarYCbCrImage.cpp

@@ -143,8 +143,21 @@ SharedPlanarYCbCrImage::SetDataNoCopy(const Data &aData)
 {
   mData = aData;
   mSize = aData.mPicSize;
+  /* SetDataNoCopy is used to update YUV plane offsets without (re)allocating
+   * memory previously allocated with AllocateAndGetNewBuffer().
+   * serializer.GetData() returns the address of the memory previously allocated
+   * with AllocateAndGetNewBuffer(), that we subtract from the Y, Cb, Cr
+   * channels to compute 0-based offsets to pass to InitializeBufferInfo.
+   */
   YCbCrImageDataSerializer serializer(mTextureClient->GetBuffer());
-  serializer.InitializeBufferInfo(aData.mYSize,
+  uint8_t *base = serializer.GetData();
+  uint32_t yOffset = aData.mYChannel - base;
+  uint32_t cbOffset = aData.mCbChannel - base;
+  uint32_t crOffset = aData.mCrChannel - base;
+  serializer.InitializeBufferInfo(yOffset,
+                                  cbOffset,
+                                  crOffset,
+                                  aData.mYSize,
                                   aData.mCbCrSize,
                                   aData.mStereoMode);
 }