Efficiently handle image layer scaling

webkit/compositor_bindings/web_layer_impl_fixed_bounds.cc

Index: webkit/compositor_bindings/web_layer_impl_fixed_bounds.cc
diff --git a/webkit/compositor_bindings/web_layer_impl_fixed_bounds.cc b/webkit/compositor_bindings/web_layer_impl_fixed_bounds.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8ae213ece345f1f61cbb84e47adf1acbdf70cb0a
--- /dev/null
+++ b/webkit/compositor_bindings/web_layer_impl_fixed_bounds.cc
@@ -0,0 +1,143 @@
+// 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.
+
+#include "webkit/compositor_bindings/web_layer_impl_fixed_bounds.h"
+
+#include "cc/layer.h"
+#include "third_party/WebKit/Source/Platform/chromium/public/WebFloatPoint.h"
+#include "third_party/WebKit/Source/Platform/chromium/public/WebSize.h"
+#include "third_party/WebKit/Source/Platform/chromium/public/WebTransformationMatrix.h"
+#include "third_party/skia/include/utils/SkMatrix44.h"
+#include "webkit/compositor_bindings/web_transformation_matrix_util.h"
+
+using cc::Layer;
+using webkit::WebTransformationMatrixUtil;
+
+namespace WebKit {
+
+WebLayerImplFixedBounds::WebLayerImplFixedBounds() {
+}
+
+WebLayerImplFixedBounds::WebLayerImplFixedBounds(scoped_refptr<Layer> layer)
+    : WebLayerImpl(layer) {
+}
+
+
+WebLayerImplFixedBounds::~WebLayerImplFixedBounds() {
+}
+
+void WebLayerImplFixedBounds::invalidateRect(const WebFloatRect& rect) {
+  // Partial invalidations seldom occur for such layers.
+  // Simply invalidate the whole layer to avoid transformation of coordinates.
+  invalidate();
+}
+
+void WebLayerImplFixedBounds::setAnchorPoint(
+    const WebFloatPoint& anchor_point) {
+  if (anchor_point != this->anchorPoint()) {
+    m_layer->setAnchorPoint(anchor_point);
+    UpdateLayerBoundsAndTransform();
+  }
+}
+
+void WebLayerImplFixedBounds::setBounds(const WebSize& bounds) {
+  if (original_bounds_ != gfx::Size(bounds)) {
+      original_bounds_ = bounds;
+      UpdateLayerBoundsAndTransform();
+  }
+}
+
+WebSize WebLayerImplFixedBounds::bounds() const {
+  return original_bounds_;
+}
+
+void WebLayerImplFixedBounds::setSublayerTransform(const SkMatrix44& matrix) {
+  gfx::Transform transform;
+  transform.matrix() = matrix;
+  SetSublayerTransformInternal(transform);
+}
+
+void WebLayerImplFixedBounds::setSublayerTransform(
+    const WebTransformationMatrix& matrix) {
+  SetSublayerTransformInternal(
+      WebTransformationMatrixUtil::ToTransform(matrix));
+}
+
+SkMatrix44 WebLayerImplFixedBounds::sublayerTransform() const {
+  return original_sublayer_transform_.matrix();
+}
+
+void WebLayerImplFixedBounds::setTransform(const SkMatrix44& matrix) {
+  gfx::Transform transform;
+  transform.matrix() = matrix;
+  SetTransformInternal(transform);
+}
+
+void WebLayerImplFixedBounds::setTransform(
+    const WebTransformationMatrix& matrix) {
+  SetTransformInternal(WebTransformationMatrixUtil::ToTransform(matrix));
+}
+
+SkMatrix44 WebLayerImplFixedBounds::transform() const {
+  return original_transform_.matrix();
+}
+
+void WebLayerImplFixedBounds::SetFixedBounds(const gfx::Size& fixed_bounds) {
+  if (fixed_bounds_ != fixed_bounds) {
+    fixed_bounds_ = fixed_bounds;
+    UpdateLayerBoundsAndTransform();
+  }
+}
+
+void WebLayerImplFixedBounds::SetSublayerTransformInternal(
+    const gfx::Transform& transform) {
+  if (original_sublayer_transform_ != transform) {
+    original_sublayer_transform_ = transform;
+    UpdateLayerBoundsAndTransform();
+  }
+}
+
+void WebLayerImplFixedBounds::SetTransformInternal(
+    const gfx::Transform& transform) {
+  if (original_transform_ != transform) {
+    original_transform_ = transform;
+    UpdateLayerBoundsAndTransform();
+  }
+}
+
+void WebLayerImplFixedBounds::UpdateLayerBoundsAndTransform()
+{
+  if (fixed_bounds_.IsEmpty() || original_bounds_.IsEmpty() ||
+      fixed_bounds_ == original_bounds_ ||
+      // For now fall back to non-fixed bounds for non-zero anchor point.
+      // TODO(wangxianzhu): Support non-zero anchor point for fixed bounds.
+      anchorPoint().x || anchorPoint().y) {
+    m_layer->setBounds(original_bounds_);
+    m_layer->setTransform(original_transform_);
+    m_layer->setSublayerTransform(original_sublayer_transform_);
+    return;
+  }
+
+  m_layer->setBounds(fixed_bounds_);
+
+  // Apply bounds scale (bounds/fixedBounds) over original transform.
+  gfx::Transform transform_with_bounds_scale(original_transform_);
+  float boundsScaleX =
+      static_cast<float>(original_bounds_.width()) / fixed_bounds_.width();
+  float boundsScaleY =
+      static_cast<float>(original_bounds_.height()) / fixed_bounds_.height();
+  transform_with_bounds_scale.Scale(boundsScaleX, boundsScaleY);
+  m_layer->setTransform(transform_with_bounds_scale);
+
+  // As we apply extra scale transform on this layer which will propagate to the
+  // sublayers, here undo the scale on sublayers.
+  gfx::Transform sublayer_transform_with_inverse_bounds_scale;
+  sublayer_transform_with_inverse_bounds_scale.Scale(1.f / boundsScaleX,
+                                                     1.f / boundsScaleY);
+  sublayer_transform_with_inverse_bounds_scale.PreconcatTransform(
+      original_sublayer_transform_);
+  m_layer->setSublayerTransform(sublayer_transform_with_inverse_bounds_scale);
+}
+
+} // namespace WebKit