Add currScanline() getter to SkCodec API

This is more correct than using nextScanline() for the
SkGifCodec scanline decoder (since we will get a strange
result in the interlaced case) and is necessary if we want
to add scanline decoding to SkIcoCodec.

This does not actually fix bugs or change behavior.

BUG=skia:

Review URL: https://codereview.chromium.org/1489163002

diff --git a/include/codec/SkCodec.h b/include/codec/SkCodec.h
index 9f28af0..075f976 100644 (file)
--- a/include/codec/SkCodec.h
+++ b/include/codec/SkCodec.h
@@ -415,9 +415,9 @@ public:
     int nextScanline() const { return this->outputScanline(fCurrScanline); }
 
     /**
-     * Returns the output y-coordinate of the row that corresponds to an input
-     * y-coordinate.  The input y-coordinate represents where the scanline
-     * is located in the encoded data.
+     *  Returns the output y-coordinate of the row that corresponds to an input
+     *  y-coordinate.  The input y-coordinate represents where the scanline
+     *  is located in the encoded data.
      *
      *  This will equal inputScanline, except in the case of strangely
      *  encoded image types (bottom-up bmps, interlaced gifs).
@@ -529,14 +529,22 @@ protected:
     virtual SkScanlineOrder onGetScanlineOrder() const { return kTopDown_SkScanlineOrder; }
 
     /**
-     *  Update the next scanline. Used by interlaced png.
+     *  Update the current scanline. Used by interlaced png.
      */
-    void updateNextScanline(int newY) { fCurrScanline = newY; }
+    void updateCurrScanline(int newY) { fCurrScanline = newY; }
 
     const SkImageInfo& dstInfo() const { return fDstInfo; }
 
     const SkCodec::Options& options() const { return fOptions; }
 
+    /**
+     *  Returns the number of scanlines that have been decoded so far.
+     *  This is unaffected by the SkScanlineOrder.
+     *
+     *  Returns -1 if we have not started a scanline decode.
+     */
+    int currScanline() const { return fCurrScanline; }
+
     virtual int onOutputScanline(int inputScanline) const;
 
 private:

diff --git a/src/codec/SkCodec_libgif.cpp b/src/codec/SkCodec_libgif.cpp
index 8021af9..e6a4016 100644 (file)
--- a/src/codec/SkCodec_libgif.cpp
+++ b/src/codec/SkCodec_libgif.cpp
@@ -508,7 +508,7 @@ SkCodec::Result SkGifCodec::onStartScanlineDecode(const SkImageInfo& dstInfo,
 
 void SkGifCodec::handleScanlineFrame(int count, int* rowsBeforeFrame, int* rowsInFrame) {
     if (fFrameIsSubset) {
-        const int currRow = this->INHERITED::nextScanline();
+        const int currRow = this->currScanline();
 
         // The number of rows that remain to be skipped before reaching rows that we
         // actually must decode into.

diff --git a/src/codec/SkCodec_libpng.cpp b/src/codec/SkCodec_libpng.cpp
index 355d493..a611705 100644 (file)
--- a/src/codec/SkCodec_libpng.cpp
+++ b/src/codec/SkCodec_libpng.cpp
@@ -768,7 +768,7 @@ public:
             if (!this->rewindIfNeeded()) {
                 return kCouldNotRewind;
             }
-            this->updateNextScanline(currScanline);
+            this->updateCurrScanline(currScanline);
         }
 
         if (setjmp(png_jmpbuf(this->png_ptr()))) {