Mark layers that can use LCD text based on layer transform and opacity.

cc/layer_tree_host_common.cc

 // 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 "cc/layer_tree_host_common.h"
 
 #include "cc/layer.h"
 #include "cc/layer_impl.h"
@@ skipping 11 matching lines @@
 namespace cc {
 
 ScrollAndScaleSet::ScrollAndScaleSet()
 {
 }
 
 ScrollAndScaleSet::~ScrollAndScaleSet()
 {
 }
 
+bool LayerTreeHostCommon::canUseLCDText()
+{
+#if OS(ANDROID)
+    return false;
+#else
+    return true;
+#endif
+}
+
 gfx::Rect LayerTreeHostCommon::calculateVisibleRect(const gfx::Rect& targetSurfaceRect, const gfx::Rect& layerBoundRect, const WebTransformationMatrix& transform)
 {
     // Is this layer fully contained within the target surface?
     gfx::Rect layerInSurfaceSpace = MathUtil::mapClippedRect(transform, layerBoundRect);
     if (targetSurfaceRect.Contains(layerInSurfaceSpace))
         return layerBoundRect;
 
     // If the layer doesn't fill up the entire surface, then find the part of
     // the surface rect where the layer could be visible. This avoids trying to
     // project surface rect points that are behind the projection point.
@@ skipping 339 matching lines @@
         replicaMaskLayer->setContentsScale(contentsScale);
 }
 
 // Recursively walks the layer tree starting at the given node and computes all the
 // necessary transformations, clipRects, render surfaces, etc.
 template<typename LayerType, typename LayerList, typename RenderSurfaceType, typename LayerSorter>
 static void calculateDrawTransformsInternal(LayerType* layer, const WebTransformationMatrix& parentMatrix,
     const WebTransformationMatrix& fullHierarchyMatrix, const WebTransformationMatrix& currentScrollCompensationMatrix,
     const gfx::Rect& clipRectFromAncestor, bool ancestorClipsSubtree,
     RenderSurfaceType* nearestAncestorThatMovesPixels, LayerList& renderSurfaceLayerList, LayerList& layerList,
-    LayerSorter* layerSorter, int maxTextureSize, float deviceScaleFactor, float pageScaleFactor, gfx::Rect& drawableContentRectOfSubtree)
+    LayerSorter* layerSorter, int maxTextureSize, float deviceScaleFactor, float pageScaleFactor, bool canUseLCDText,
+    gfx::Rect& drawableContentRectOfSubtree)
 {
     // This function computes the new matrix transformations recursively for this
     // layer and all its descendants. It also computes the appropriate render surfaces.
     // Some important points to remember:
     //
     // 0. Here, transforms are notated in Matrix x Vector order, and in words we describe what
     //    the transform does from left to right.
     //
     // 1. In our terminology, the "layer origin" refers to the top-left corner of a layer, and the
     //    positive Y-axis points downwards. This interpretation is valid because the orthographic
@@ skipping 133 matching lines @@
     layerScreenSpaceTransform.multiply(drawTransform);
     layer->setScreenSpaceTransform(layerScreenSpaceTransform);
 
     bool animatingTransformToTarget = layer->transformIsAnimating();
     bool animatingTransformToScreen = animatingTransformToTarget;
     if (layer->parent()) {
         animatingTransformToTarget |= layer->parent()->drawTransformIsAnimating();
         animatingTransformToScreen |= layer->parent()->screenSpaceTransformIsAnimating();
     }
 
+    // Adjusting text AA method during animation may cause repaints, which in-turn jank.
+    bool canAdjustTextAA = !drawOpacityIsAnimating && !animatingTransformToScreen;
+    // To avoid color fringing, LCD text should only be used on opaque layers with just integral translation.
+    bool layerCanUseLCDText = canAdjustTextAA ? canUseLCDText && (drawOpacity == 1.0) && drawTransform.isIntegerTranslation() : false;

[danakj, 2012/11/07 18:15:00]

This statement is weird to me. It is essentially:

layerCanUseLCDText = canAdjustTextAA && canUseLCDText && (drawOpacity == 1.0) &&
drawTransform.isIntegerTranslation()

If that is what you mean, can you write it that way instead of with a
conditional? But it seems a little odd.

If a surface-owning layer is animating opacity, then canUseLCDText will become
false.

Within the surface, opacity won't be animating, but canUseLCDText is false,
because of the surface "cant adjust AA".

In the end, I think the result would be right, but it would be the same with or
without the canAdjustTextAA included in this statement here.

[alokp, 2012/11/08 22:34:07]

You are right. The logic to NOT mess with text AA setting while animation is
active was not correct. To fix this I had to add a
Layer::screenSpaceOpacityisAnimating.

+
     gfx::RectF contentRect(gfx::PointF(), layer->contentBounds());
 
     // fullHierarchyMatrix is the matrix that transforms objects between screen space (except projection matrix) and the most recent RenderSurfaceImpl's space.
     // nextHierarchyMatrix will only change if this layer uses a new RenderSurfaceImpl, otherwise remains the same.
     WebTransformationMatrix nextHierarchyMatrix = fullHierarchyMatrix;
     WebTransformationMatrix sublayerMatrix;
 
     gfx::Vector2dF renderSurfaceSublayerScale = MathUtil::computeTransform2dScaleComponents(combinedTransform);
 
     if (subtreeShouldRenderToSeparateSurface(layer, isScaleOrTranslation(combinedTransform))) {
@@ skipping 65 matching lines @@
             nearestAncestorThatMovesPixels = renderSurface;
 
         // The render surface clipRect is expressed in the space where this surface draws, i.e. the same space as clipRectFromAncestor.
         if (ancestorClipsSubtree)
             renderSurface->setClipRect(clipRectFromAncestor);
         else
             renderSurface->setClipRect(gfx::Rect());
 
         renderSurface->setNearestAncestorThatMovesPixels(nearestAncestorThatMovesPixels);
 
+        // If the new render surface is drawn translucent or with a non-integral translation
+        // then the subtree that gets drawn on this render surface cannot use LCD text.
+        canUseLCDText = layerCanUseLCDText;
+
         renderSurfaceLayerList.push_back(layer);
     } else {
         DCHECK(layer->parent());
 
         layer->setDrawTransform(drawTransform);
         layer->setDrawTransformIsAnimating(animatingTransformToTarget);
         layer->setScreenSpaceTransformIsAnimating(animatingTransformToScreen);
         sublayerMatrix = combinedTransform;
 
         layer->setDrawOpacity(drawOpacity);
         layer->setDrawOpacityIsAnimating(drawOpacityIsAnimating);
 
         layer->clearRenderSurface();
 
         // Layers without renderSurfaces directly inherit the ancestor's clip status.
         subtreeShouldBeClipped = ancestorClipsSubtree;
         if (ancestorClipsSubtree)
             clipRectForSubtree = clipRectFromAncestor;
 
         // Layers that are not their own renderTarget will render into the target of their nearest ancestor.
         layer->setRenderTarget(layer->parent()->renderTarget());
     }
 
+    if (canAdjustTextAA)
+        layer->setCanUseLCDText(layerCanUseLCDText);
+
     gfx::Rect rectInTargetSpace = ToEnclosingRect(MathUtil::mapClippedRect(layer->drawTransform(), contentRect));
 
     if (layerClipsSubtree(layer)) {
         subtreeShouldBeClipped = true;
         if (ancestorClipsSubtree && !layer->renderSurface()) {
             clipRectForSubtree = clipRectFromAncestor;
             clipRectForSubtree.Intersect(rectInTargetSpace);
         } else
             clipRectForSubtree = rectInTargetSpace;
     }
@@ skipping 16 matching lines @@
         descendants.push_back(layer);
 
     WebTransformationMatrix nextScrollCompensationMatrix = computeScrollCompensationMatrixForChildren(layer, parentMatrix, currentScrollCompensationMatrix);;
 
     gfx::Rect accumulatedDrawableContentRectOfChildren;
     for (size_t i = 0; i < layer->children().size(); ++i) {
         LayerType* child = LayerTreeHostCommon::getChildAsRawPtr(layer->children(), i);
         gfx::Rect drawableContentRectOfChildSubtree;
         calculateDrawTransformsInternal<LayerType, LayerList, RenderSurfaceType, LayerSorter>(child, sublayerMatrix, nextHierarchyMatrix, nextScrollCompensationMatrix,
                                                                                               clipRectForSubtree, subtreeShouldBeClipped, nearestAncestorThatMovesPixels,
-                                                                                              renderSurfaceLayerList, descendants, layerSorter, maxTextureSize, deviceScaleFactor, pageScaleFactor, drawableContentRectOfChildSubtree);
+                                                                                              renderSurfaceLayerList, descendants, layerSorter, maxTextureSize, deviceScaleFactor, pageScaleFactor, canUseLCDText,
+                                                                                              drawableContentRectOfChildSubtree);
         if (!drawableContentRectOfChildSubtree.IsEmpty()) {
             accumulatedDrawableContentRectOfChildren.Union(drawableContentRectOfChildSubtree);
             if (child->renderSurface())
                 descendants.push_back(child);
         }
     }
 
     // Compute the total drawableContentRect for this subtree (the rect is in targetSurface space)
     gfx::Rect localDrawableContentRectOfSubtree = accumulatedDrawableContentRectOfChildren;
     if (layer->drawsContent())
@@ skipping 117 matching lines @@
     bool subtreeShouldBeClipped = true;
     gfx::Rect deviceViewportRect(gfx::Point(), deviceViewportSize);
 
     // This function should have received a root layer.
     DCHECK(isRootLayer(rootLayer));
 
     cc::calculateDrawTransformsInternal<Layer, std::vector<scoped_refptr<Layer> >, RenderSurface, void>(
         rootLayer, deviceScaleTransform, identityMatrix, identityMatrix,
         deviceViewportRect, subtreeShouldBeClipped, 0, renderSurfaceLayerList,
         dummyLayerList, 0, maxTextureSize,
-        deviceScaleFactor, pageScaleFactor, totalDrawableContentRect);
+        deviceScaleFactor, pageScaleFactor, canUseLCDText(), totalDrawableContentRect);
 
     // The dummy layer list should not have been used.
     DCHECK(dummyLayerList.size() == 0);
     // A root layer renderSurface should always exist after calculateDrawTransforms.
     DCHECK(rootLayer->renderSurface());
 }
 
 void LayerTreeHostCommon::calculateDrawTransforms(LayerImpl* rootLayer, const gfx::Size& deviceViewportSize, float deviceScaleFactor, float pageScaleFactor, LayerSorter* layerSorter, int maxTextureSize, std::vector<LayerImpl*>& renderSurfaceLayerList)
 {
     gfx::Rect totalDrawableContentRect;
     WebTransformationMatrix identityMatrix;
     WebTransformationMatrix deviceScaleTransform;
     deviceScaleTransform.scale(deviceScaleFactor);
     std::vector<LayerImpl*> dummyLayerList;
 
     // The root layer's renderSurface should receive the deviceViewport as the initial clipRect.
     bool subtreeShouldBeClipped = true;
     gfx::Rect deviceViewportRect(gfx::Point(), deviceViewportSize);
 
     // This function should have received a root layer.
     DCHECK(isRootLayer(rootLayer));
 
     cc::calculateDrawTransformsInternal<LayerImpl, std::vector<LayerImpl*>, RenderSurfaceImpl, LayerSorter>(
         rootLayer, deviceScaleTransform, identityMatrix, identityMatrix,
         deviceViewportRect, subtreeShouldBeClipped, 0, renderSurfaceLayerList,
         dummyLayerList, layerSorter, maxTextureSize,
-        deviceScaleFactor, pageScaleFactor, totalDrawableContentRect);
+        deviceScaleFactor, pageScaleFactor, canUseLCDText(), totalDrawableContentRect);
 
     // The dummy layer list should not have been used.
     DCHECK(dummyLayerList.size() == 0);
     // A root layer renderSurface should always exist after calculateDrawTransforms.
     DCHECK(rootLayer->renderSurface());
 }
 
 static bool pointHitsRect(const gfx::PointF& screenSpacePoint, const WebTransformationMatrix& localSpaceToScreenSpaceTransform, gfx::RectF localSpaceRect)
 {
     // If the transform is not invertible, then assume that this point doesn't hit this rect.
@@ skipping 59 matching lines @@
 
         foundLayer = currentLayer;
         break;
     }
 
     // This can potentially return 0, which means the screenSpacePoint did not successfully hit test any layers, not even the root layer.
     return foundLayer;
 }
 
 }  // namespace cc