Fill incomplete images in SkCodec parent class

src/codec/SkJpegCodec.cpp

Index: src/codec/SkJpegCodec.cpp
diff --git a/src/codec/SkJpegCodec.cpp b/src/codec/SkJpegCodec.cpp
index 4557e45673eb124a4ae346467b77a21cc955f8fa..5d5acc02e6efc238873a72a0af0730ca8005af8b 100644
--- a/src/codec/SkJpegCodec.cpp
+++ b/src/codec/SkJpegCodec.cpp
@@ -303,7 +303,8 @@ bool SkJpegCodec::nativelyScaleToDimensions(uint32_t dstWidth, uint32_t dstHeigh
  */
 SkCodec::Result SkJpegCodec::onGetPixels(const SkImageInfo& dstInfo,
                                          void* dst, size_t dstRowBytes,
-                                         const Options& options, SkPMColor*, int*) {
+                                         const Options& options, SkPMColor*, int*,
+                                         int* incompleteScanlines) {
     // Rewind the stream if needed
     if (!this->rewindIfNeeded()) {
         return fDecoderMgr->returnFailure("could not rewind stream", kCouldNotRewind);
@@ -350,16 +351,7 @@ SkCodec::Result SkJpegCodec::onGetPixels(const SkImageInfo& dstInfo,
 
         // If we cannot read enough rows, assume the input is incomplete
         if (rowsDecoded != 1) {
-            // Fill the remainder of the image with black. This error handling
-            // behavior is unspecified but SkCodec consistently uses black as
-            // the fill color for opaque images.  If the destination is kGray,
-            // the low 8 bits of SK_ColorBLACK will be used.  Conveniently,
-            // these are zeros, which is the representation for black in kGray.
-            // If the destination is kRGB_565, the low 16 bits of SK_ColorBLACK
-            // will be used.  Conveniently, these are zeros, which is the
-            // representation for black in kRGB_565.
-            SkSwizzler::Fill(dstRow, dstInfo, dstRowBytes, dstHeight - y,
-                    SK_ColorBLACK, nullptr, options.fZeroInitialized);
+            *incompleteScanlines = dstHeight - y;
 
             // Prevent libjpeg from failing on incomplete decode
             dinfo->output_scanline = dstHeight;
@@ -387,8 +379,8 @@ SkCodec::Result SkJpegCodec::onGetPixels(const SkImageInfo& dstInfo,
  */
 class SkJpegScanlineDecoder : public SkScanlineDecoder {
 public:
-    SkJpegScanlineDecoder(const SkImageInfo& srcInfo, SkJpegCodec* codec)
-        : INHERITED(srcInfo)
+    SkJpegScanlineDecoder(SkJpegCodec* codec)
+        : INHERITED(codec, codec->getInfo())
         , fCodec(codec)
         , fOpts()
     {}
@@ -425,8 +417,8 @@ public:
                 SkASSERT(false);
         }
 
-        fSwizzler.reset(SkSwizzler::CreateSwizzler(srcConfig, nullptr, info, options.fZeroInitialized, 
-                                                   this->getInfo()));
+        fSwizzler.reset(SkSwizzler::CreateSwizzler(srcConfig, nullptr, info,
+                options.fZeroInitialized, this->getInfo()));
         if (!fSwizzler) {
             // FIXME: CreateSwizzler could fail for another reason.
             return SkCodec::kUnimplemented;
@@ -496,7 +488,7 @@ public:
         jpeg_finish_decompress(fCodec->fDecoderMgr->dinfo());
     }
 
-    SkCodec::Result onGetScanlines(void* dst, int count, size_t rowBytes) override {
+    uint32_t onGetScanlines(void* dst, int count, size_t rowBytes) override {
         // Set the jump location for libjpeg errors
         if (setjmp(fCodec->fDecoderMgr->getJmpBuf())) {
             return fCodec->fDecoderMgr->returnFailure("setjmp", SkCodec::kInvalidInput);
@@ -515,10 +507,8 @@ public:
             // Read row of the image
             uint32_t rowsDecoded = jpeg_read_scanlines(fCodec->fDecoderMgr->dinfo(), &dstRow, 1);
             if (rowsDecoded != 1) {
-                SkSwizzler::Fill(dstRow, this->dstInfo(), rowBytes, count - y,
-                        SK_ColorBLACK, nullptr, fOpts.fZeroInitialized);
                 fCodec->fDecoderMgr->dinfo()->output_scanline = this->dstInfo().height();
-                return SkCodec::kIncompleteInput;
+                return y;
             }
 
             // Convert to RGBA if necessary
@@ -534,7 +524,7 @@ public:
                 dstRow = SkTAddOffset<JSAMPLE>(dstRow, rowBytes);
             }
         }
-        return SkCodec::kSuccess;
+        return count;
     }
 
 #ifndef TURBO_HAS_SKIP
@@ -548,15 +538,13 @@ public:
     }
 #endif
 
-    SkCodec::Result onSkipScanlines(int count) override {
+    uint32_t onSkipScanlines(int count) override {
         // Set the jump location for libjpeg errors
         if (setjmp(fCodec->fDecoderMgr->getJmpBuf())) {
             return fCodec->fDecoderMgr->returnFailure("setjmp", SkCodec::kInvalidInput);
         }
 
-        jpeg_skip_scanlines(fCodec->fDecoderMgr->dinfo(), count);
-
-        return SkCodec::kSuccess;
+        return jpeg_skip_scanlines(fCodec->fDecoderMgr->dinfo(), count);
     }
 
     SkEncodedFormat onGetEncodedFormat() const override {
@@ -564,7 +552,7 @@ public:
     }
 
 private:
-    SkAutoTDelete<SkJpegCodec> fCodec;
+    SkJpegCodec*               fCodec;      // Owned by parent class
     SkAutoMalloc               fStorage;    // Only used if sampling is needed
     uint8_t*                   fSrcRow;     // Only used if sampling is needed
     SkCodec::Options           fOpts;
@@ -579,8 +567,6 @@ SkScanlineDecoder* SkJpegCodec::NewSDFromStream(SkStream* stream) {
         return nullptr;
     }
 
-    const SkImageInfo& srcInfo = codec->getInfo();
-
     // Return the new scanline decoder
-    return new SkJpegScanlineDecoder(srcInfo, codec.detach());
+    return new SkJpegScanlineDecoder(codec.detach());
 }