Add subsetting to SkScaledCodec

src/codec/SkCodec_libgif.cpp

Index: src/codec/SkCodec_libgif.cpp
diff --git a/src/codec/SkCodec_libgif.cpp b/src/codec/SkCodec_libgif.cpp
index 036285360b47040f49b04db4a8db8e3bceb746fc..e483aa01ad9558e556ef1de3c40edbd2863264fe 100644
--- a/src/codec/SkCodec_libgif.cpp
+++ b/src/codec/SkCodec_libgif.cpp
@@ -100,7 +100,7 @@ static uint32_t find_trans_index(const SavedImage& image) {
  * It is used in a SkAutoTCallIProc template
  */
 void SkGifCodec::CloseGif(GifFileType* gif) {
-    DGifCloseFile(gif, NULL);
+    DGifCloseFile(gif, nullptr);
 }
 
 /*
@@ -108,7 +108,7 @@ void SkGifCodec::CloseGif(GifFileType* gif) {
  * decoder
  */
 void SkGifCodec::FreeExtension(SavedImage* image) {
-    if (NULL != image->ExtensionBlocks) {
+    if (nullptr != image->ExtensionBlocks) {
         GifFreeExtensions(&image->ExtensionBlockCount, &image->ExtensionBlocks);
     }
 }
@@ -220,9 +220,9 @@ SkGifCodec::SkGifCodec(const SkImageInfo& srcInfo, SkStream* stream, GifFileType
     // there is a valid background color.
     , fFillIndex(0)
     , fFrameRect(frameRect)
-    , fFrameIsSubset(frameIsSubset)
-    , fColorTable(NULL)
-    , fSwizzler(NULL)
+    , fFrameIsSubset(false)
+    , fColorTable(nullptr)
+    , fSwizzler(nullptr)
 {}
 
 bool SkGifCodec::onRewind() {
@@ -355,7 +355,7 @@ void SkGifCodec::initializeColorTable(const SkImageInfo& dstInfo, SkPMColor* inp
     // Set up our own color table
     const uint32_t maxColors = 256;
     SkPMColor colorPtr[256];
-    if (NULL != inputColorCount) {
+    if (nullptr != inputColorCount) {
         // We set the number of colors to maxColors in order to ensure
         // safe memory accesses.  Otherwise, an invalid pixel could
         // access memory outside of our color table array.
@@ -365,12 +365,12 @@ void SkGifCodec::initializeColorTable(const SkImageInfo& dstInfo, SkPMColor* inp
     // Get local color table
     ColorMapObject* colorMap = fGif->Image.ColorMap;
     // If there is no local color table, use the global color table
-    if (NULL == colorMap) {
+    if (nullptr == colorMap) {
         colorMap = fGif->SColorMap;
     }
 
     uint32_t colorCount = 0;
-    if (NULL != colorMap) {
+    if (nullptr != colorMap) {
         colorCount = colorMap->ColorCount;
         // giflib guarantees these properties
         SkASSERT(colorCount == (unsigned) (1 << (colorMap->BitsPerPixel)));
@@ -425,10 +425,10 @@ SkCodec::Result SkGifCodec::prepareToDecode(const SkImageInfo& dstInfo, SkPMColo
 }
 
 SkCodec::Result SkGifCodec::initializeSwizzler(const SkImageInfo& dstInfo,
-        ZeroInitialized zeroInit) {
+        ZeroInitialized zeroInit, int subsetLeft, int subsetWidth) {
     const SkPMColor* colorPtr = get_color_ptr(fColorTable.get());
-    fSwizzler.reset(SkSwizzler::CreateSwizzler(SkSwizzler::kIndex,
-            colorPtr, dstInfo, zeroInit));
+    fSwizzler.reset(SkSwizzler::CreateSwizzler(SkSwizzler::kIndex, colorPtr, dstInfo, zeroInit,
+            subsetLeft, subsetWidth));
     if (nullptr != fSwizzler.get()) {
         return kSuccess;
     }
@@ -460,7 +460,8 @@ SkCodec::Result SkGifCodec::onGetPixels(const SkImageInfo& dstInfo,
     // Initialize the swizzler
     if (fFrameIsSubset) {
         const SkImageInfo subsetDstInfo = dstInfo.makeWH(fFrameRect.width(), fFrameRect.height());
-        if (kSuccess != this->initializeSwizzler(subsetDstInfo, opts.fZeroInitialized)) {
+        if (kSuccess != this->initializeSwizzler(subsetDstInfo, opts.fZeroInitialized, 0,
+                fFrameRect.width())) {
             return gif_error("Could not initialize swizzler.\n", kUnimplemented);
         }
 
@@ -474,7 +475,8 @@ SkCodec::Result SkGifCodec::onGetPixels(const SkImageInfo& dstInfo,
         dst = SkTAddOffset<void*>(dst, dstRowBytes * fFrameRect.top() +
                 dstBytesPerPixel * fFrameRect.left());
     } else {
-        if (kSuccess != this->initializeSwizzler(dstInfo, opts.fZeroInitialized)) {
+        if (kSuccess != this->initializeSwizzler(dstInfo, opts.fZeroInitialized, 0,
+                dstInfo.width())) {
             return gif_error("Could not initialize swizzler.\n", kUnimplemented);
         }
     }
@@ -499,7 +501,8 @@ uint32_t SkGifCodec::onGetFillValue(SkColorType colorType, SkAlphaType alphaType
 }
 
 SkCodec::Result SkGifCodec::onStartScanlineDecode(const SkImageInfo& dstInfo,
-        const SkCodec::Options& opts, SkPMColor inputColorPtr[], int* inputColorCount) {
+        const SkCodec::Options& opts, SkPMColor inputColorPtr[], int* inputColorCount,
+        int subsetLeft, int subsetWidth) {
 
     Result result = this->prepareToDecode(dstInfo, inputColorPtr, inputColorCount, this->options());
     if (kSuccess != result) {
@@ -509,11 +512,13 @@ SkCodec::Result SkGifCodec::onStartScanlineDecode(const SkImageInfo& dstInfo,
     // Initialize the swizzler
     if (fFrameIsSubset) {
         const SkImageInfo subsetDstInfo = dstInfo.makeWH(fFrameRect.width(), fFrameRect.height());
-        if (kSuccess != this->initializeSwizzler(subsetDstInfo, opts.fZeroInitialized)) {
+        if (kSuccess != this->initializeSwizzler(subsetDstInfo, opts.fZeroInitialized, subsetLeft,
+                subsetWidth)) {
             return gif_error("Could not initialize swizzler.\n", kUnimplemented);
         }
     } else {
-        if (kSuccess != this->initializeSwizzler(dstInfo, opts.fZeroInitialized)) {
+        if (kSuccess != this->initializeSwizzler(dstInfo, opts.fZeroInitialized, subsetLeft,
+                subsetWidth)) {
             return gif_error("Could not initialize swizzler.\n", kUnimplemented);
         }
     }