Title: [117313] trunk/Source/WebCore
- Revision
- 117313
- Author
- timothy_hor...@apple.com
- Date
- 2012-05-16 11:41:38 -0700 (Wed, 16 May 2012)
Log Message
FrameView::scrollContentsFastPath should use painted area to determine whether to drop out of the fast path
https://bugs.webkit.org/show_bug.cgi?id=86651
<rdar://problem/11459243>
Reviewed by Simon Fraser.
Previously, we decided to fall out of the fast scrolling path by the number of fixed-position elements
on the page. This was less than ideal if a single fixed position element took up a significant portion
of the page, or if there were many small, cheap-to-paint fixed elements.
Instead, we should use the fast path if less than 50% of the page will be repainted by fixed-position
elements, and otherwise fall back to the slow path.
I've tested a few different thresholds with an internal test; 50% seems to work relatively well,
but the ideal value is hard to determine and likely depends on hardware.
No new tests, performance improvement with few large fixed-position objects or many small ones.
* page/FrameView.cpp:
(WebCore::FrameView::scrollContentsFastPath):
Modified Paths
Diff
Modified: trunk/Source/WebCore/ChangeLog (117312 => 117313)
--- trunk/Source/WebCore/ChangeLog 2012-05-16 18:31:53 UTC (rev 117312)
+++ trunk/Source/WebCore/ChangeLog 2012-05-16 18:41:38 UTC (rev 117313)
@@ -1,3 +1,26 @@
+2012-05-16 Tim Horton <timothy_hor...@apple.com>
+
+ FrameView::scrollContentsFastPath should use painted area to determine whether to drop out of the fast path
+ https://bugs.webkit.org/show_bug.cgi?id=86651
+ <rdar://problem/11459243>
+
+ Reviewed by Simon Fraser.
+
+ Previously, we decided to fall out of the fast scrolling path by the number of fixed-position elements
+ on the page. This was less than ideal if a single fixed position element took up a significant portion
+ of the page, or if there were many small, cheap-to-paint fixed elements.
+
+ Instead, we should use the fast path if less than 50% of the page will be repainted by fixed-position
+ elements, and otherwise fall back to the slow path.
+
+ I've tested a few different thresholds with an internal test; 50% seems to work relatively well,
+ but the ideal value is hard to determine and likely depends on hardware.
+
+ No new tests, performance improvement with few large fixed-position objects or many small ones.
+
+ * page/FrameView.cpp:
+ (WebCore::FrameView::scrollContentsFastPath):
+
2012-05-16 David Reveman <reve...@chromium.org>
[Chromium] Use ThrottledTextureUploader with threaded compositing.
Modified: trunk/Source/WebCore/page/FrameView.cpp (117312 => 117313)
--- trunk/Source/WebCore/page/FrameView.cpp 2012-05-16 18:31:53 UTC (rev 117312)
+++ trunk/Source/WebCore/page/FrameView.cpp 2012-05-16 18:41:38 UTC (rev 117313)
@@ -1454,8 +1454,6 @@
bool FrameView::scrollContentsFastPath(const IntSize& scrollDelta, const IntRect& rectToScroll, const IntRect& clipRect)
{
- const size_t fixedObjectThreshold = 5;
-
RenderBlock::PositionedObjectsListHashSet* positionedObjects = 0;
if (RenderView* root = rootRenderer(this))
positionedObjects = root->positionedObjects();
@@ -1468,8 +1466,7 @@
const bool isCompositedContentLayer = contentsInCompositedLayer();
// Get the rects of the fixed objects visible in the rectToScroll
- Vector<IntRect, fixedObjectThreshold> subRectToUpdate;
- bool updateInvalidatedSubRect = true;
+ Region regionToUpdate;
RenderBlock::PositionedObjectsListHashSet::const_iterator end = positionedObjects->end();
for (RenderBlock::PositionedObjectsListHashSet::const_iterator it = positionedObjects->begin(); it != end; ++it) {
RenderBox* renderBox = *it;
@@ -1483,45 +1480,40 @@
updateRect = contentsToRootView(updateRect);
if (!isCompositedContentLayer && clipsRepaints())
updateRect.intersect(rectToScroll);
- if (!updateRect.isEmpty()) {
- if (subRectToUpdate.size() >= fixedObjectThreshold) {
- updateInvalidatedSubRect = false;
- break;
- }
- subRectToUpdate.append(updateRect);
- }
+ if (!updateRect.isEmpty())
+ regionToUpdate.unite(updateRect);
}
- // Scroll the view
- if (updateInvalidatedSubRect) {
- // 1) scroll
- hostWindow()->scroll(scrollDelta, rectToScroll, clipRect);
+ // The area to be painted by fixed objects exceeds 50% of the area of the view, we cannot use the fast path.
+ if (regionToUpdate.totalArea() > (clipRect.width() * clipRect.height() * 0.5))
+ return false;
- // 2) update the area of fixed objects that has been invalidated
- size_t fixObjectsCount = subRectToUpdate.size();
- for (size_t i = 0; i < fixObjectsCount; ++i) {
- IntRect updateRect = subRectToUpdate[i];
- IntRect scrolledRect = updateRect;
- scrolledRect.move(scrollDelta);
- updateRect.unite(scrolledRect);
+ // 1) scroll
+ hostWindow()->scroll(scrollDelta, rectToScroll, clipRect);
+
+ // 2) update the area of fixed objects that has been invalidated
+ Vector<IntRect> subRectsToUpdate = regionToUpdate.rects();
+ size_t fixObjectsCount = subRectsToUpdate.size();
+ for (size_t i = 0; i < fixObjectsCount; ++i) {
+ IntRect updateRect = subRectsToUpdate[i];
+ IntRect scrolledRect = updateRect;
+ scrolledRect.move(scrollDelta);
+ updateRect.unite(scrolledRect);
#if USE(ACCELERATED_COMPOSITING)
- if (isCompositedContentLayer) {
- updateRect = rootViewToContents(updateRect);
- RenderView* root = rootRenderer(this);
- ASSERT(root);
- root->layer()->setBackingNeedsRepaintInRect(updateRect);
- continue;
- }
-#endif
- if (clipsRepaints())
- updateRect.intersect(rectToScroll);
- hostWindow()->invalidateContentsAndRootView(updateRect, false);
+ if (isCompositedContentLayer) {
+ updateRect = rootViewToContents(updateRect);
+ RenderView* root = rootRenderer(this);
+ ASSERT(root);
+ root->layer()->setBackingNeedsRepaintInRect(updateRect);
+ continue;
}
- return true;
+#endif
+ if (clipsRepaints())
+ updateRect.intersect(rectToScroll);
+ hostWindow()->invalidateContentsAndRootView(updateRect, false);
}
- // the number of fixed objects exceed the threshold, we cannot use the fast path
- return false;
+ return true;
}
void FrameView::scrollContentsSlowPath(const IntRect& updateRect)
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