Refactoring DrawLooper so that it can apply shadow effects as skia image filters

Source/core/platform/graphics/DrawLooper.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 13 matching lines @@
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef DrawLooper_h
 #define DrawLooper_h
 
+#include "SkRefCnt.h"
+#include "core/platform/graphics/Color.h"
+#include "core/platform/graphics/FloatSize.h"
 #include "wtf/Noncopyable.h"
+#include "wtf/RefCounted.h"
 #include "wtf/RefPtr.h"
+#include "wtf/Vector.h"
 
+class SkBitmap;
 class SkDrawLooper;
+class SkImageFilter;
 class SkLayerDrawLooper;
 
 namespace WebCore {
 
-class Color;
-class FloatSize;
-
-class DrawLooper {
+class DrawLooper : public RefCounted<DrawLooper> {
     // Implementing the copy constructor properly would require writing code to
     // copy the underlying SkDrawLooper.
     WTF_MAKE_NONCOPYABLE(DrawLooper);
 
 public:
     enum ShadowTransformMode {
         ShadowRespectsTransforms,
         ShadowIgnoresTransforms
     };
     enum ShadowAlphaMode {
         ShadowRespectsAlpha,
         ShadowIgnoresAlpha
     };
 
     DrawLooper();
     ~DrawLooper();
 
     // Callees should not modify this looper other than to iterate over it.
     // A downcast to SkLayerDrawLooper* is tantamount to a const_cast.
     SkDrawLooper* skDrawLooper() const;
+    SkImageFilter* imageFilter() const;
 
     void addUnmodifiedContent();
     void addShadow(const FloatSize& offset, float blur, const Color&,
         ShadowTransformMode = ShadowRespectsTransforms,
         ShadowAlphaMode = ShadowRespectsAlpha);
 
+    bool shouldUseImageFilterToDrawBitmap(const SkBitmap&);

[Stephen White, 2013/08/26 19:04:23]

Maybe this one should be const too?

+
 private:
-    RefPtr<SkLayerDrawLooper> m_skDrawLooper;
+    enum LayerType {
+        ShadowLayer,
+        UnmodifiedLayer
+    };
+    void clearCached();
+    void buildCachedDrawLooper() const;
+    void buildCachedImageFilter() const;
+
+    struct DrawLooperLayerInfo {
+        FloatSize m_offset;
+        float m_blur;
+        Color m_color;
+        ShadowTransformMode m_shadowTransformMode;
+        ShadowAlphaMode m_shadowAlphaMode;
+        LayerType m_layerType;
+    };
+
+    typedef Vector<DrawLooperLayerInfo, 2> LayerVector;
+
+    LayerVector m_layerInfo;
+
+    mutable RefPtr<SkLayerDrawLooper> m_cachedDrawLooper;
+    mutable RefPtr<SkImageFilter> m_cachedImageFilter;
 };
 
 } // namespace WebCore
 
 #endif // DrawLooper_h