Mark layers whether they can use LCD text depending on content-opacity, draw-opacity, and draw-tran…

cc/CCLayerTreeHostCommon.cpp

Index: cc/CCLayerTreeHostCommon.cpp
diff --git a/cc/CCLayerTreeHostCommon.cpp b/cc/CCLayerTreeHostCommon.cpp
index 24274a6f6f59f4213fdfc1fe73a6070a74b84329..d10002461cd33209656c3bf4d62a9c396fc48c8d 100644
--- a/cc/CCLayerTreeHostCommon.cpp
+++ b/cc/CCLayerTreeHostCommon.cpp
@@ -363,7 +363,7 @@ void setupRootLayerAndSurfaceForRecursion(LayerType* rootLayer, LayerList& rende
 template<typename LayerType, typename LayerList, typename RenderSurfaceType, typename LayerSorter>
 static void calculateDrawTransformsInternal(LayerType* layer, LayerType* rootLayer, const WebTransformationMatrix& parentMatrix,
     const WebTransformationMatrix& fullHierarchyMatrix, const WebTransformationMatrix& currentScrollCompensationMatrix,
-    const IntRect& clipRectFromAncestor, bool ancestorClipsSubtree,
+    const IntRect& clipRectFromAncestor, bool ancestorClipsSubtree, bool canUseLCDText,
     RenderSurfaceType* nearestAncestorThatMovesPixels, LayerList& renderSurfaceLayerList, LayerList& layerList,
     LayerSorter* layerSorter, int maxTextureSize, float deviceScaleFactor, IntRect& drawableContentRectOfSubtree)
 {
@@ -512,6 +512,9 @@ static void calculateDrawTransformsInternal(LayerType* layer, LayerType* rootLay
         animatingTransformToScreen |= layer->parent()->screenSpaceTransformIsAnimating();
     }
 
+    bool shouldAdjustTextAA = !(drawOpacityIsAnimating || animatingTransformToScreen);
+    bool layerCanUseLCDText = shouldAdjustTextAA ? canUseLCDText && (drawOpacity == 1.0) && drawTransform.isIntegerTranslation() : false;
+
     FloatRect contentRect(FloatPoint(), layer->contentBounds());
 
     // fullHierarchyMatrix is the matrix that transforms objects between screen space (except projection matrix) and the most recent RenderSurface's space.
@@ -567,6 +570,10 @@ static void calculateDrawTransformsInternal(LayerType* layer, LayerType* rootLay
         // current target surface space that could cause more w < 0 headaches.
         subtreeShouldBeClipped = false;
 
+        // If the new renderSurface is drawn translucent or with a non-integral translation
+        // then the subtree that gets drawn on this renderSurface cannot use LCD text.
+        canUseLCDText = layerCanUseLCDText;
+
         if (layer->maskLayer()) {
             layer->maskLayer()->setRenderTarget(layer);
             layer->maskLayer()->setVisibleContentRect(IntRect(IntPoint(), layer->contentBounds()));
@@ -619,6 +626,9 @@ static void calculateDrawTransformsInternal(LayerType* layer, LayerType* rootLay
         }
     }
 
+    if (shouldAdjustTextAA)
+        layer->setCanUseLCDText(layerCanUseLCDText);
+
     IntRect rectInTargetSpace = enclosingIntRect(CCMathUtil::mapClippedRect(layer->drawTransform(), contentRect));
 
     if (layerClipsSubtree(layer)) {
@@ -654,7 +664,7 @@ static void calculateDrawTransformsInternal(LayerType* layer, LayerType* rootLay
         LayerType* child = CCLayerTreeHostCommon::getChildAsRawPtr(layer->children(), i);
         IntRect drawableContentRectOfChildSubtree;
         calculateDrawTransformsInternal<LayerType, LayerList, RenderSurfaceType, LayerSorter>(child, rootLayer, sublayerMatrix, nextHierarchyMatrix, nextScrollCompensationMatrix,
-                                                                                              clipRectForSubtree, subtreeShouldBeClipped, nearestAncestorThatMovesPixels,
+                                                                                              clipRectForSubtree, subtreeShouldBeClipped, canUseLCDText, nearestAncestorThatMovesPixels,
                                                                                               renderSurfaceLayerList, descendants, layerSorter, maxTextureSize, deviceScaleFactor, drawableContentRectOfChildSubtree);
         if (!drawableContentRectOfChildSubtree.isEmpty()) {
             accumulatedDrawableContentRectOfChildren.unite(drawableContentRectOfChildSubtree);
@@ -773,7 +783,7 @@ void CCLayerTreeHostCommon::calculateDrawTransforms(LayerChromium* rootLayer, co
     setupRootLayerAndSurfaceForRecursion<LayerChromium, std::vector<scoped_refptr<LayerChromium> > >(rootLayer, renderSurfaceLayerList, deviceViewportSize);
 
     cc::calculateDrawTransformsInternal<LayerChromium, std::vector<scoped_refptr<LayerChromium> >, RenderSurfaceChromium, void>(rootLayer, rootLayer, deviceScaleTransform, identityMatrix, identityMatrix,
-                                                                                                                         rootLayer->renderSurface()->contentRect(), true, 0, renderSurfaceLayerList,
+                                                                                                                         rootLayer->renderSurface()->contentRect(), true, true, 0, renderSurfaceLayerList,
                                                                                                                          rootLayer->renderSurface()->layerList(), 0, maxTextureSize, deviceScaleFactor, totalDrawableContentRect);
 }
 
@@ -787,7 +797,7 @@ void CCLayerTreeHostCommon::calculateDrawTransforms(CCLayerImpl* rootLayer, cons
     setupRootLayerAndSurfaceForRecursion<CCLayerImpl, std::vector<CCLayerImpl*> >(rootLayer, renderSurfaceLayerList, deviceViewportSize);
 
     cc::calculateDrawTransformsInternal<CCLayerImpl, std::vector<CCLayerImpl*>, CCRenderSurface, CCLayerSorter>(rootLayer, rootLayer, deviceScaleTransform, identityMatrix, identityMatrix,
-                                                                                                                rootLayer->renderSurface()->contentRect(), true, 0, renderSurfaceLayerList,
+                                                                                                                rootLayer->renderSurface()->contentRect(), true, true, 0, renderSurfaceLayerList,
                                                                                                                 rootLayer->renderSurface()->layerList(), layerSorter, maxTextureSize, deviceScaleFactor, totalDrawableContentRect);
 }