Allow ico decoder to decode PNG sub-images.

Since Windows Vista, PNG can be embedded in an ICO file. Update
our decoder to support this.

BUG=https://code.google.com/p/skia/issues/detail?id=1398
R=djsollen@google.com

Review URL: https://codereview.chromium.org/18655007

git-svn-id: http://skia.googlecode.com/svn/trunk@9932 2bbb7eff-a529-9590-31e7-b0007b416f81

include/core/SkImageDecoder.h

@@ -404,7 +404,17 @@ protected:
                     int dstX, int dstY, int width, int height,
                     int srcX, int srcY);
 
+    /**
+     *  Copy all fields on this decoder to the other decoder. Used by subclasses
+     *  to decode a subimage using a different decoder, but with the same settings.
+     */
+    void copyFieldsToOther(SkImageDecoder* other);
 
+    /**
+     *  Return the default preference being used by the current or latest call to
+     *  decode.
+     */
+    SkBitmap::Config getDefaultPref() { return fDefaultPref; }
 
     /** Can be queried from within onDecode, to see if the user (possibly in
         a different thread) has requested the decode to cancel. If this returns

src/images/SkImageDecoder.cpp

@@ -50,6 +50,23 @@ SkImageDecoder::~SkImageDecoder() {
     SkSafeUnref(fAllocator);
 }
 
+void SkImageDecoder::copyFieldsToOther(SkImageDecoder* other) {
+    if (NULL == other) {
+        return;
+    }
+    other->setPeeker(fPeeker);
+    other->setChooser(fChooser);
+    other->setAllocator(fAllocator);
+    other->setSampleSize(fSampleSize);
+    if (fUsePrefTable) {
+        other->setPrefConfigTable(fPrefTable);
+    } else {
+        other->fDefaultPref = fDefaultPref;
+    }
+    other->setPreferQualityOverSpeed(fPreferQualityOverSpeed);
+    other->setRequireUnpremultipliedColors(fRequireUnpremultipliedColors);
+}
+
 SkImageDecoder::Format SkImageDecoder::getFormat() const {
     return kUnknown_Format;
 }

src/images/SkImageDecoder_libico.cpp

@@ -152,6 +152,20 @@ bool SkICOImageDecoder::onDecode(SkStream* stream, SkBitmap* bm, Mode mode)
     int offset = read4Bytes(buf, 18 + choice*16);
     if ((size_t)(offset + size) > length)
         return false;
+
+    // Check to see if this is a PNG image inside the ICO
+    {
+        SkMemoryStream subStream(buf + offset, size, false);
+        SkAutoTDelete<SkImageDecoder> otherDecoder(SkImageDecoder::Factory(&subStream));
+        if (otherDecoder.get() != NULL) {
+            // Set fields on the other decoder to be the same as this one.
+            this->copyFieldsToOther(otherDecoder.get());
+            if(otherDecoder->decode(&subStream, bm, this->getDefaultPref(), mode)) {
+                return true;
+            }
+        }
+    }
+
     //int infoSize = read4Bytes(buf, offset);             //40
     //int width = read4Bytes(buf, offset+4);              //should == w
     //int height = read4Bytes(buf, offset+8);             //should == 2*h

src/ports/SkImageDecoder_empty.cpp

@@ -22,6 +22,8 @@ SkImageDecoder* SkImageDecoder::Factory(SkStream*) {
     return NULL;
 }
 
+void SkImageDecoder::copyFieldsToOther(SkImageDecoder* ) {}
+
 bool SkImageDecoder::DecodeFile(const char[], SkBitmap*, SkBitmap::Config,
                                 SkImageDecoder::Mode, SkImageDecoder::Format*) {
     return false;