Inline RenderLayer::beginTransparencyLayers into RenderBox::paintLayerContents.

sky/engine/core/rendering/RenderBox.cpp

Index: sky/engine/core/rendering/RenderBox.cpp
diff --git a/sky/engine/core/rendering/RenderBox.cpp b/sky/engine/core/rendering/RenderBox.cpp
index d97b921c5b138d3576e7737a8451761dc49b1021..4d4a814a9b0154c1612437f15f66275769d55bb5 100644
--- a/sky/engine/core/rendering/RenderBox.cpp
+++ b/sky/engine/core/rendering/RenderBox.cpp
@@ -741,6 +741,53 @@ void RenderBox::paintLayer(GraphicsContext* context, const LayerPaintingInfo& pa
     layer()->parent()->restoreClip(context, paintingInfo.paintDirtyRect, clipRect);
 }
 
+static LayoutRect transparencyClipBox(const RenderLayer*, const RenderLayer* rootLayer, const LayoutSize& subPixelAccumulation);
+
+static void expandClipRectForDescendantsAndReflection(LayoutRect& clipRect, const RenderLayer* layer, const RenderLayer* rootLayer,
+    const LayoutSize& subPixelAccumulation)
+{
+    // Note: we don't have to walk z-order lists since transparent elements always establish
+    // a stacking container. This means we can just walk the layer tree directly.
+    for (RenderLayer* curr = layer->firstChild(); curr; curr = curr->nextSibling())
+        clipRect.unite(transparencyClipBox(curr, rootLayer, subPixelAccumulation));
+}
+
+static LayoutRect transparencyClipBox(const RenderLayer* layer, const RenderLayer* rootLayer,
+    const LayoutSize& subPixelAccumulation)
+{
+    // FIXME: Although this function completely ignores CSS-imposed clipping, we did already intersect with the
+    // paintDirtyRect, and that should cut down on the amount we have to paint.  Still it
+    // would be better to respect clips.
+
+    if (rootLayer != layer && layer->transform()) {
+        // The best we can do here is to use enclosed bounding boxes to establish a "fuzzy" enough clip to encompass
+        // the transformed layer and all of its children.
+        const RenderLayer* rootLayerForTransform = rootLayer;
+        LayoutPoint delta;
+        layer->convertToLayerCoords(rootLayerForTransform, delta);
+
+        delta.move(subPixelAccumulation);
+        IntPoint pixelSnappedDelta = roundedIntPoint(delta);
+        TransformationMatrix transform;
+        transform.translate(pixelSnappedDelta.x(), pixelSnappedDelta.y());
+        transform = transform * *layer->transform();
+
+        // We don't use fragment boxes when collecting a transformed layer's bounding box, since it always
+        // paints unfragmented.y
+        LayoutRect clipRect = layer->physicalBoundingBox(layer);
+        expandClipRectForDescendantsAndReflection(clipRect, layer, layer, subPixelAccumulation);
+        layer->renderer()->style()->filterOutsets().expandRect(clipRect);
+        LayoutRect result = transform.mapRect(clipRect);
+        return result;
+    }
+
+    LayoutRect clipRect = layer->physicalBoundingBox(rootLayer);
+    expandClipRectForDescendantsAndReflection(clipRect, layer, rootLayer, subPixelAccumulation);
+    layer->renderer()->style()->filterOutsets().expandRect(clipRect);
+    clipRect.move(subPixelAccumulation);
+    return clipRect;
+}
+
 void RenderBox::paintLayerContents(GraphicsContext* context, const LayerPaintingInfo& paintingInfo)
 {
     float deviceScaleFactor = blink::deviceScaleFactor(frame());
@@ -788,8 +835,13 @@ void RenderBox::paintLayerContents(GraphicsContext* context, const LayerPainting
         }
     }
 
-    if (layer()->isTransparent())
-        layer()->beginTransparencyLayers(context, localPaintingInfo.rootLayer, paintingInfo.paintDirtyRect, localPaintingInfo.subPixelAccumulation);
+    if (layer()->isTransparent()) {
+        context->save();
+        LayoutRect clipRect = intersection(paintingInfo.paintDirtyRect,
+            transparencyClipBox(layer(), localPaintingInfo.rootLayer, localPaintingInfo.subPixelAccumulation));
+        context->clip(clipRect);
+        context->beginTransparencyLayer(opacity());
+    }
 
     layer()->clipToRect(localPaintingInfo, context, contentRect);