Efficiently handle image layer scaling

webkit/compositor_bindings/web_layer_impl_fixed_bounds.h

+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef WebLayerImplFixedBounds_h
+#define WebLayerImplFixedBounds_h
+
+#include "ui/gfx/size.h"
+#include "ui/gfx/transform.h"
+#include "webkit/compositor_bindings/web_layer_impl.h"
+
+namespace WebKit {
+
+// A special implementation of WebLayerImpl for layers that its contents
+// need to be automatically scaled when the bounds changes. The compositor
+// can efficiently handle the bounds change of such layers if the bounds
+// is fixed to a given value and the change of bounds are converted to
+// transformation scales.
+class WebLayerImplFixedBounds : public WebLayerImpl {
+ public:
+  WEBKIT_COMPOSITOR_BINDINGS_EXPORT WebLayerImplFixedBounds();
+  WEBKIT_COMPOSITOR_BINDINGS_EXPORT explicit WebLayerImplFixedBounds(
+      scoped_refptr<cc::Layer>);
+  virtual ~WebLayerImplFixedBounds();
+
+  // WebLayerImpl overrides.
+  virtual void invalidateRect(const WebFloatRect&) OVERRIDE;
+  virtual void setAnchorPoint(const WebFloatPoint&) OVERRIDE;
+  virtual void setBounds(const WebSize&) OVERRIDE;
+  virtual WebSize bounds() const OVERRIDE;
+  virtual void setSublayerTransform(const SkMatrix44&) OVERRIDE;
+  virtual void setSublayerTransform(const WebTransformationMatrix&) OVERRIDE;
+  virtual SkMatrix44 sublayerTransform() const OVERRIDE;
+  virtual void setTransform(const SkMatrix44&) OVERRIDE;
+  virtual void setTransform(const WebTransformationMatrix&) OVERRIDE;
+  virtual SkMatrix44 transform() const OVERRIDE;
+
+  WEBKIT_COMPOSITOR_BINDINGS_EXPORT void SetFixedBounds(const gfx::Size&);
+
+ protected:
+  void SetTransformInternal(const gfx::Transform&);
+  void SetSublayerTransformInternal(const gfx::Transform&);
+  void UpdateLayerBoundsAndTransform();
+
+  gfx::Transform original_sublayer_transform_;
+  gfx::Transform original_transform_;
+  gfx::Size original_bounds_;
+  gfx::Size fixed_bounds_;
+};
+
+} // namespace WebKit
+
+#endif // WebLayerImplFixedBounds_h