Changeset 238876 in webkit

Timestamp:

Dec 4, 2018 2:58:36 PM (5 years ago)

Author:

Simon Fraser

Message:

REGRESSION (r238090): position:fixed sidebar on ​https://www.w3.org/TR/SVG2/coords.html does not stay fixed
​https://bugs.webkit.org/show_bug.cgi?id=192320
<rdar://problem/46429833>

Reviewed by Zalan Bujtas.
Source/WebCore:

Re-land r238840 with a more reliable test.

When we fall into slow scrolling mode (for example, because of background-attachment: fixed),
RenderLayerCompositor::updateCompositingLayers() needs to set the geometry dirty bit on layers
for viewport-constrained objects so we update them.

This is only necessary for page scrolling; for overflow scrolls, updateLayerPositions() already
does enough dirtying that fixed layers nested inside scrollers get updated.

Test: compositing/fixed-with-main-thread-scrolling.html

• rendering/RenderLayerCompositor.cpp:

(WebCore::RenderLayerCompositor::updateCompositingLayers):

LayoutTests:

• compositing/fixed-with-main-thread-scrolling-expected.html: Added.
• compositing/fixed-with-main-thread-scrolling.html: Added.
• platform/ios/TestExpectations:

Location:

trunk

Files:

• LayoutTests/ChangeLog (modified) (1 diff)
• LayoutTests/compositing/fixed-with-main-thread-scrolling-expected.html (added)
• LayoutTests/compositing/fixed-with-main-thread-scrolling.html (added)
• LayoutTests/platform/ios/TestExpectations (modified) (1 diff)
• Source/WebCore/ChangeLog (modified) (1 diff)
• Source/WebCore/rendering/RenderLayerCompositor.cpp (modified) (1 diff)

trunk/LayoutTests/ChangeLog

@@ +1 @@
+2018-12-04  Simon Fraser  <simon.fraser@apple.com>
+
+        REGRESSION (r238090): position:fixed sidebar on https://www.w3.org/TR/SVG2/coords.html does not stay fixed
+        https://bugs.webkit.org/show_bug.cgi?id=192320
+        <rdar://problem/46429833>
+
+        Reviewed by Zalan Bujtas.
+
+        * compositing/fixed-with-main-thread-scrolling-expected.html: Added.
+        * compositing/fixed-with-main-thread-scrolling.html: Added.
+        * platform/ios/TestExpectations:
+
 2018-12-04  Youenn Fablet  <youenn@apple.com>
 

trunk/LayoutTests/platform/ios/TestExpectations

@@ -795 +795 @@
 
 # These tests rely on EventSender.keydown(), which is not supported on iOS
+compositing/fixed-with-main-thread-scrolling.html [ Skip ]
 editing/caret/emoji.html [ WontFix ]
 editing/deleting/5729680.html [ Skip ]

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2018-12-04  Simon Fraser  <simon.fraser@apple.com>
+
+        REGRESSION (r238090): position:fixed sidebar on https://www.w3.org/TR/SVG2/coords.html does not stay fixed
+        https://bugs.webkit.org/show_bug.cgi?id=192320
+        <rdar://problem/46429833>
+
+        Reviewed by Zalan Bujtas.
+        
+        Re-land r238840 with a more reliable test.
+        
+        When we fall into slow scrolling mode (for example, because of background-attachment: fixed),
+        RenderLayerCompositor::updateCompositingLayers() needs to set the geometry dirty bit on layers
+        for viewport-constrained objects so we update them.
+        
+        This is only necessary for page scrolling; for overflow scrolls, updateLayerPositions() already
+        does enough dirtying that fixed layers nested inside scrollers get updated.
+
+        Test: compositing/fixed-with-main-thread-scrolling.html
+
+        * rendering/RenderLayerCompositor.cpp:
+        (WebCore::RenderLayerCompositor::updateCompositingLayers):
+
 2018-12-04  Youenn Fablet  <youenn@apple.com>
 

trunk/Source/WebCore/rendering/RenderLayerCompositor.cpp

@@ -667 +667 @@
         enableCompositingMode(true);
 
+    bool isPageScroll = !updateRoot || updateRoot == &rootRenderLayer();
     updateRoot = &rootRenderLayer();
 
     if (updateType == CompositingUpdateType::OnScroll || updateType == CompositingUpdateType::OnCompositedScroll) {
+        // We only get here if we didn't scroll on the scrolling thread, so this update needs to re-position viewport-constrained layers.
+        if (m_renderView.settings().acceleratedCompositingForFixedPositionEnabled() && isPageScroll) {
+            if (auto* viewportConstrainedObjects = m_renderView.frameView().viewportConstrainedObjects()) {
+                for (auto* renderer : *viewportConstrainedObjects) {
+                    if (auto* layer = renderer->layer())
+                        layer->setNeedsCompositingGeometryUpdate();
+                }
+            }
+        }
+
         // Scrolling can affect overlap. FIXME: avoid for page scrolling.
         updateRoot->setDescendantsNeedCompositingRequirementsTraversal();