Changeset 224265 in webkit

Timestamp:

Oct 31, 2017 5:21:20 PM (7 years ago)

Author:

Simon Fraser

Message:

Rubber-banding overflow-scrolling-touch shows black
​https://bugs.webkit.org/show_bug.cgi?id=179087
rdar://problem/35260253

Reviewed by Sam Weinig.

Source/WebCore:

The "backgroundIsKnownToBeObscured" optimization was kicking in for an overflow:scroll
whose area was completely covered by its contents, which happens with overlay scrollbars.

However, this ignored the fact that you can rubber-band to reveal the background, and,
on iOS, composited scrolling requires that the scroller background is painted since it goes
into its own layer.

Fix by turning off the optimization for layers that scroll overflow, including those
using composited scrolling.

Test: fast/scrolling/rubber-band-shows-background.html

• rendering/RenderBox.cpp:

(WebCore::RenderBox::foregroundIsKnownToBeOpaqueInRect const):
(WebCore::RenderBox::computeBackgroundIsKnownToBeObscured):

• rendering/RenderLayer.cpp:

(WebCore::RenderLayer::scrollTo):
(WebCore::RenderLayer::calculateClipRects const):

• rendering/RenderLayer.h:

LayoutTests:

• fast/scrolling/rubber-band-shows-background-expected.html: Added.
• fast/scrolling/rubber-band-shows-background.html: Added.

Location:

trunk

Files:

• LayoutTests/ChangeLog (modified) (1 diff)
• LayoutTests/fast/scrolling/rubber-band-shows-background-expected.html (added)
• LayoutTests/fast/scrolling/rubber-band-shows-background.html (added)
• Source/WebCore/ChangeLog (modified) (1 diff)
• Source/WebCore/rendering/RenderBox.cpp (modified) (2 diffs)
• Source/WebCore/rendering/RenderLayer.cpp (modified) (2 diffs)
• Source/WebCore/rendering/RenderLayer.h (modified) (2 diffs)

trunk/LayoutTests/ChangeLog

@@ +1 @@
+2017-10-31  Simon Fraser  <simon.fraser@apple.com>
+
+        Rubber-banding overflow-scrolling-touch shows black
+        https://bugs.webkit.org/show_bug.cgi?id=179087
+        rdar://problem/35260253
+
+        Reviewed by Sam Weinig.
+
+        * fast/scrolling/rubber-band-shows-background-expected.html: Added.
+        * fast/scrolling/rubber-band-shows-background.html: Added.
+
 2017-10-31  Ryan Haddad  <ryanhaddad@apple.com>
 

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2017-10-31  Simon Fraser  <simon.fraser@apple.com>
+
+        Rubber-banding overflow-scrolling-touch shows black
+        https://bugs.webkit.org/show_bug.cgi?id=179087
+        rdar://problem/35260253
+
+        Reviewed by Sam Weinig.
+
+        The "backgroundIsKnownToBeObscured" optimization was kicking in for an overflow:scroll
+        whose area was completely covered by its contents, which happens with overlay scrollbars.
+
+        However, this ignored the fact that you can rubber-band to reveal the background, and,
+        on iOS, composited scrolling requires that the scroller background is painted since it goes
+        into its own layer.
+
+        Fix by turning off the optimization for layers that scroll overflow, including those
+        using composited scrolling.
+
+        Test: fast/scrolling/rubber-band-shows-background.html
+
+        * rendering/RenderBox.cpp:
+        (WebCore::RenderBox::foregroundIsKnownToBeOpaqueInRect const):
+        (WebCore::RenderBox::computeBackgroundIsKnownToBeObscured):
+        * rendering/RenderLayer.cpp:
+        (WebCore::RenderLayer::scrollTo):
+        (WebCore::RenderLayer::calculateClipRects const):
+        * rendering/RenderLayer.h:
+
 2017-10-31  Tim Horton  <timothy_horton@apple.com>
 

trunk/Source/WebCore/rendering/RenderBox.cpp

@@ -1419 +1419 @@
     if (!maxDepthToTest)
         return false;
+
     for (auto& childBox : childrenOfType<RenderBox>(*this)) {
         if (!isCandidateForOpaquenessTest(childBox))
@@ -1456 +1457 @@
     if (!getBackgroundPaintedExtent(paintOffset, backgroundRect))
         return false;
+
+    if (hasLayer() && layer()->scrollingMayRevealBackground())
+        return false;
+
     return foregroundIsKnownToBeOpaqueInRect(backgroundRect, backgroundObscurationTestMaxDepth);
 }

trunk/Source/WebCore/rendering/RenderLayer.cpp

@@ -2387 +2387 @@
         return;
     }
-    
+
     m_scrollPosition = newPosition;
 
@@ -5983 +5983 @@
 }
 
+bool RenderLayer::scrollingMayRevealBackground() const
+{
+    return scrollsOverflow() || usesCompositedScrolling();
+}
+
 bool RenderLayer::backgroundIsKnownToBeOpaqueInRect(const LayoutRect& localRect) const
 {

trunk/Source/WebCore/rendering/RenderLayer.h

@@ -676 +676 @@
     bool backgroundIsKnownToBeOpaqueInRect(const LayoutRect&) const;
 
+    bool scrollingMayRevealBackground() const;
+
     bool containsDirtyOverlayScrollbars() const { return m_containsDirtyOverlayScrollbars; }
     void setContainsDirtyOverlayScrollbars(bool dirtyScrollbars) { m_containsDirtyOverlayScrollbars = dirtyScrollbars; }
@@ -884 +886 @@
 
     bool shouldBeNormalFlowOnly() const;
-
     bool shouldBeSelfPaintingLayer() const;