Changeset 168670 in webkit

Timestamp:

May 12, 2014, 9:32:09 PM (11 years ago)

Author:

Simon Fraser

Message:

[iOS] Fixed items are sometimes clipped after rubber-banding
​https://bugs.webkit.org/show_bug.cgi?id=132851
<rdar://problem/16870790>

Reviewed by Benjamin Poulain.

On iOS fixed-position layers would get clipped to the document rect,
but with rubber-banding, we can now have a custom fixed postion rect
that extends outside the document rect.

Another issue was that we would un-composite fixed elements sometimes
when scrolling fast, again because they could fall outside of the document rect.

A final issue was that pinching could reveal parts of fixed elements that should
lie outside the viewport, rather than clipping the layers.

Fix by converting both call points to use viewportConstrainedVisibleContentRect()
rather than viewportConstrainedExtentRect(). On non-iOS platforms these are
the same, but on iOS viewportConstrainedVisibleContentRect() uses the
custom fixed position rect, which is the correct rect to intersect with.

• rendering/RenderLayerBacking.cpp:

(WebCore::RenderLayerBacking::updateCompositedBounds):

• rendering/RenderLayerCompositor.cpp:

(WebCore::RenderLayerCompositor::requiresCompositingForPosition):

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• rendering/RenderLayerBacking.cpp (modified) (1 diff)
• rendering/RenderLayerCompositor.cpp (modified) (1 diff)

trunk/Source/WebCore/ChangeLog ¶

@@ +1 @@
+2014-05-12  Simon Fraser  <simon.fraser@apple.com>
+
+        [iOS] Fixed items are sometimes clipped after rubber-banding
+        https://bugs.webkit.org/show_bug.cgi?id=132851
+        <rdar://problem/16870790>
+
+        Reviewed by Benjamin Poulain.
+
+        On iOS fixed-position layers would get clipped to the document rect,
+        but with rubber-banding, we can now have a custom fixed postion rect
+        that extends outside the document rect.
+        
+        Another issue was that we would un-composite fixed elements sometimes
+        when scrolling fast, again because they could fall outside of the document rect.
+        
+        A final issue was that pinching could reveal parts of fixed elements that should
+        lie outside the viewport, rather than clipping the layers.
+        
+        Fix by converting both call points to use viewportConstrainedVisibleContentRect()
+        rather than viewportConstrainedExtentRect(). On non-iOS platforms these are
+        the same, but on iOS viewportConstrainedVisibleContentRect() uses the
+        custom fixed position rect, which is the correct rect to intersect with.
+
+        * rendering/RenderLayerBacking.cpp:
+        (WebCore::RenderLayerBacking::updateCompositedBounds):
+        * rendering/RenderLayerCompositor.cpp:
+        (WebCore::RenderLayerCompositor::requiresCompositingForPosition):
+
 2014-05-06  Jon Honeycutt  <jhoneycutt@apple.com>
 

trunk/Source/WebCore/rendering/RenderLayerBacking.cpp ¶

@@ -456 +456 @@
         LayoutRect clippingBounds;
         if (renderer().style().position() == FixedPosition && renderer().container() == &view)
-            clippingBounds = view.frameView().viewportConstrainedExtentRect();
+            clippingBounds = view.frameView().viewportConstrainedVisibleContentRect();
         else
             clippingBounds = view.unscaledDocumentRect();

trunk/Source/WebCore/rendering/RenderLayerCompositor.cpp ¶

@@ -2630 +2630 @@
 
     // Fixed position elements that are invisible in the current view don't get their own layer.
-    LayoutRect viewBounds = m_renderView.frameView().viewportConstrainedExtentRect();
+    LayoutRect viewBounds = m_renderView.frameView().viewportConstrainedVisibleContentRect();
     LayoutRect layerBounds = layer.calculateLayerBounds(&layer, 0, RenderLayer::UseLocalClipRectIfPossible | RenderLayer::IncludeLayerFilterOutsets | RenderLayer::UseFragmentBoxes
         | RenderLayer::ExcludeHiddenDescendants | RenderLayer::DontConstrainForMask | RenderLayer::IncludeCompositedDescendants);