mark all SkImage methods const, so we can make it thread-safe

src/image/SkImage_Codec.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkImageDecoder.h"
 #include "SkImage_Base.h"
 #include "SkBitmap.h"
 #include "SkCanvas.h"
 #include "SkData.h"
 
 class SkImage_Codec : public SkImage_Base {
 public:
     static SkImage* NewEmpty();
 
     SkImage_Codec(SkData* encodedData, int width, int height);
     virtual ~SkImage_Codec();
 
-    virtual void onDraw(SkCanvas*, SkScalar, SkScalar, const SkPaint*) SK_OVERRIDE;
-    virtual void onDrawRectToRect(SkCanvas*, const SkRect*, const SkRect&, const SkPaint*) SK_OVERRIDE;
+    virtual void onDraw(SkCanvas*, SkScalar, SkScalar, const SkPaint*) const SK_OVERRIDE;
+    virtual void onDrawRectToRect(SkCanvas*, const SkRect*, const SkRect&,
+                                  const SkPaint*) const SK_OVERRIDE;
 
 private:
     SkData*     fEncodedData;
     SkBitmap    fBitmap;
 
     typedef SkImage_Base INHERITED;
 };
 
 ///////////////////////////////////////////////////////////////////////////////
 
 SkImage_Codec::SkImage_Codec(SkData* data, int width, int height) : INHERITED(width, height) {
     fEncodedData = data;
     fEncodedData->ref();
 }
 
 SkImage_Codec::~SkImage_Codec() {
     fEncodedData->unref();
 }
 
-void SkImage_Codec::onDraw(SkCanvas* canvas, SkScalar x, SkScalar y, const SkPaint* paint) {
+void SkImage_Codec::onDraw(SkCanvas* canvas, SkScalar x, SkScalar y, const SkPaint* paint) const {
     if (!fBitmap.pixelRef()) {
-        if (!SkImageDecoder::DecodeMemory(fEncodedData->bytes(), fEncodedData->size(), &fBitmap)) {
+        // todo: this needs to be thread-safe
+        SkBitmap* bitmap = const_cast<SkBitmap*>(&fBitmap);
+        if (!SkImageDecoder::DecodeMemory(fEncodedData->bytes(), fEncodedData->size(), bitmap)) {
             return;
         }
     }
     canvas->drawBitmap(fBitmap, x, y, paint);
 }
 
-void SkImage_Codec::onDrawRectToRect(SkCanvas* canvas, const SkRect* src,
-                                     const SkRect& dst, const SkPaint* paint) {
+void SkImage_Codec::onDrawRectToRect(SkCanvas* canvas, const SkRect* src, const SkRect& dst,
+                                     const SkPaint* paint) const {
     if (!fBitmap.pixelRef()) {
-        if (!SkImageDecoder::DecodeMemory(fEncodedData->bytes(), fEncodedData->size(), &fBitmap)) {
+        // todo: this needs to be thread-safe
+        SkBitmap* bitmap = const_cast<SkBitmap*>(&fBitmap);
+        if (!SkImageDecoder::DecodeMemory(fEncodedData->bytes(), fEncodedData->size(), bitmap)) {
             return;
         }
     }
     canvas->drawBitmapRectToRect(fBitmap, src, dst, paint);
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 SkImage* SkImage::NewEncodedData(SkData* data) {
     if (NULL == data) {
         return NULL;
     }
 
     SkBitmap bitmap;
     if (!SkImageDecoder::DecodeMemory(data->bytes(), data->size(), &bitmap, kUnknown_SkColorType,
                                       SkImageDecoder::kDecodeBounds_Mode)) {
         return NULL;
     }
 
     return SkNEW_ARGS(SkImage_Codec, (data, bitmap.width(), bitmap.height()));
 }