Chromium compositor change implementing page-scale driven pinch-zoom.

cc/CCLayerTreeHostCommon.cpp

 // Copyright 2011 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 "config.h"
 
 #include "CCLayerTreeHostCommon.h"
 
 #include "CCLayerImpl.h"
@@ skipping 253 matching lines @@
     //           -- this is just a translation by scrollDelta.
     //     Step 3. transform back to target surface space.
     //           -- this transform is the "partialLayerOriginTransform" = (parentMatrix * scale(layer->pageScaleDelta()));
     //
     // These steps create a matrix that both start and end in targetSurfaceSpace. So this matrix can
     // pre-multiply any fixed-position layer's drawTransform to undo the scrollDeltas -- as long as
     // that fixed position layer is fixed onto the same renderTarget as this scrollingLayer.
     //
 
     WebTransformationMatrix partialLayerOriginTransform = parentMatrix;
-    partialLayerOriginTransform.scale(scrollingLayer->pageScaleDelta());
+    partialLayerOriginTransform.multiply(scrollingLayer->implTransform());
 
     WebTransformationMatrix scrollCompensationForThisLayer = partialLayerOriginTransform; // Step 3
     scrollCompensationForThisLayer.translate(scrollingLayer->scrollDelta().width(), scrollingLayer->scrollDelta().height()); // Step 2
     scrollCompensationForThisLayer.multiply(partialLayerOriginTransform.inverse()); // Step 1
     return scrollCompensationForThisLayer;
 }
 
 WebTransformationMatrix computeScrollCompensationMatrixForChildren(LayerChromium* currentLayer, const WebTransformationMatrix& currentParentMatrix, const WebTransformationMatrix& currentScrollCompensation)
 {
     // The main thread (i.e. LayerChromium) does not need to worry about scroll compensation.
@@ skipping 176 matching lines @@
 
     IntSize bounds = layer->bounds();
     FloatPoint anchorPoint = layer->anchorPoint();
     FloatPoint position = layer->position() - layer->scrollDelta();
 
     // Offset between anchor point and the center of the quad.
     float centerOffsetX = (0.5 - anchorPoint.x()) * bounds.width();
     float centerOffsetY = (0.5 - anchorPoint.y()) * bounds.height();
 
     WebTransformationMatrix layerLocalTransform;
-    // LT = S[pageScaleDelta]
-    layerLocalTransform.scale(layer->pageScaleDelta());
-    // LT = S[pageScaleDelta] * Tr[origin] * Tr[origin2anchor]
+    // LT = M[impl transformation]
+    layerLocalTransform.multiply(layer->implTransform());
+    // LT = M[impl transformation] * Tr[origin] * Tr[origin2anchor]
     layerLocalTransform.translate3d(position.x() + anchorPoint.x() * bounds.width(), position.y() + anchorPoint.y() * bounds.height(), layer->anchorPointZ());
-    // LT = S[pageScaleDelta] * Tr[origin] * Tr[origin2anchor] * M[layer]
+    // LT = M[impl transformation] * Tr[origin] * Tr[origin2anchor] * M[layer]
     layerLocalTransform.multiply(layer->transform());
-    // LT = S[pageScaleDelta] * Tr[origin] * Tr[origin2anchor] * M[layer] * Tr[anchor2center]
+    // LT = M[impl transformation] * Tr[origin] * Tr[origin2anchor] * M[layer] * Tr[anchor2center]
     layerLocalTransform.translate3d(centerOffsetX, centerOffsetY, -layer->anchorPointZ());
 
     WebTransformationMatrix combinedTransform = parentMatrix;
     combinedTransform.multiply(layerLocalTransform);
 
     if (layer->fixedToContainerLayer()) {
         // Special case: this layer is a composited fixed-position layer; we need to
         // explicitly compensate for all ancestors' nonzero scrollDeltas to keep this layer
         // fixed correctly.
         combinedTransform = currentScrollCompensationMatrix * combinedTransform;
@@ skipping 397 matching lines @@
 
         foundLayer = currentLayer;
         break;
     }
 
     // This can potentially return 0, which means the viewportPoint did not successfully hit test any layers, not even the root layer.
     return foundLayer;
 }
 
 } // namespace cc