Changeset 249091 in webkit

Timestamp:

Aug 24, 2019 7:14:30 PM (5 years ago)

Author:

Simon Fraser

Message:

Have RenderLayer::calculateClipRects() use offsetFromAncestor() when possible
​https://bugs.webkit.org/show_bug.cgi?id=201066

Reviewed by Dean Jackson.

offsetFromAncestor() is a layer tree walk, so faster than localToContainerPoint(),
but we can't use it when there are transforms on the layer and intermediates up
to the ancestor.

canUseConvertToLayerCoords() was trying to answer the question about whether it's
OK to use offsetFromAncestor() (which calls convertToLayerCoords() internally), but
it has insufficient information to make a determination. Leave this issue alone, but
at least rename canUseConvertToLayerCoords().

• rendering/RenderLayer.cpp:

(WebCore::RenderLayer::updateLayerPositions):
(WebCore::RenderLayer::calculateClipRects const):

• rendering/RenderLayer.h:

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• rendering/RenderLayer.cpp (modified) (3 diffs)
• rendering/RenderLayer.h (modified) (1 diff)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2019-08-24  Simon Fraser  <simon.fraser@apple.com>
+
+        Have RenderLayer::calculateClipRects() use offsetFromAncestor() when possible
+        https://bugs.webkit.org/show_bug.cgi?id=201066
+
+        Reviewed by Dean Jackson.
+
+        offsetFromAncestor() is a layer tree walk, so faster than localToContainerPoint(),
+        but we can't use it when there are transforms on the layer and intermediates up
+        to the ancestor.
+        
+        canUseConvertToLayerCoords() was trying to answer the question about whether it's
+        OK to use offsetFromAncestor() (which calls convertToLayerCoords() internally), but
+        it has insufficient information to make a determination. Leave this issue alone, but
+        at least rename canUseConvertToLayerCoords().
+
+        * rendering/RenderLayer.cpp:
+        (WebCore::RenderLayer::updateLayerPositions):
+        (WebCore::RenderLayer::calculateClipRects const):
+        * rendering/RenderLayer.h:
+
 2019-08-24  Simon Fraser  <simon.fraser@apple.com>
 

trunk/Source/WebCore/rendering/RenderLayer.cpp

@@ -940 +940 @@
         else {
             // FIXME: It looks suspicious to call convertToLayerCoords here
-            // as canUseConvertToLayerCoords may be true for an ancestor layer.
+            // as canUseOffsetFromAncestor may be true for an ancestor layer.
             offsetFromRoot = offsetFromAncestor(root());
         }
@@ -5658 +5658 @@
 #endif
         // This layer establishes a clip of some kind.
-
-        // This offset cannot use convertToLayerCoords, because sometimes our rootLayer may be across
-        // some transformed layer boundary, for example, in the RenderLayerCompositor overlapMap, where
-        // clipRects are needed in view space.
-        LayoutPoint offset(renderer().localToContainerPoint(FloatPoint(), &clipRectsContext.rootLayer->renderer()));
+        LayoutPoint offset;
+        if (!m_hasTransformedAncestor && canUseOffsetFromAncestor())
+            offset = toLayoutPoint(offsetFromAncestor(clipRectsContext.rootLayer, AdjustForColumns));
+        else
+            offset = LayoutPoint(renderer().localToContainerPoint(FloatPoint(), &clipRectsContext.rootLayer->renderer()));
+
         if (clipRects.fixed() && &clipRectsContext.rootLayer->renderer() == &renderer().view())
             offset -= toLayoutSize(renderer().view().frameView().scrollPositionForFixedPosition());
@@ -6289 +6290 @@
             continue;
 
-        if (!childLayer->canUseConvertToLayerCoords())
+        if (!childLayer->canUseOffsetFromAncestor())
             continue;
 

trunk/Source/WebCore/rendering/RenderLayer.h

@@ -635 +635 @@
     bool hasAncestorWithFilterOutsets() const;
 
-    bool canUseConvertToLayerCoords() const
-    {
-        // These RenderObject have an impact on their layers' without them knowing about it.
+    bool canUseOffsetFromAncestor() const
+    {
+        // FIXME: This really needs to know if there are transforms on this layer and any of the layers
+        // between it and the ancestor in question.
         return !renderer().hasTransform() && !renderer().isSVGRoot();
     }