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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/185576">185576</a></dd>
<dt>Author</dt> <dd>simon.fraser@apple.com</dd>
<dt>Date</dt> <dd>2015-06-15 19:10:58 -0700 (Mon, 15 Jun 2015)</dd>
</dl>
<h3>Log Message</h3>
<pre>[iOS WK2] position:fixed elements sometimes truncated on scroll view bouncing
https://bugs.webkit.org/show_bug.cgi?id=146000
rdar://problem/19448439
Reviewed by Benjamin Poulain.
When in the middle of a rubber-band (UIScrollView bounce), we could send a bad
fixed position rect down to WebCore, causing 100% height elements to get laid out
at the wrong height, possible too short. This occurred when -_updateVisibleContentRects
said we were in a stable state, but the rubber-band offset caused WebPageProxy::computeCustomFixedPositionRect()
to compute a bad rect via constrainedUnobscuredRect.intersect(documentRect).
Fix by not claiming to be in a stable state during rubber-banding. Added _scrollViewIsRubberBanding
to compute that, taking care with floating point comparisons for 3x devices.
* UIProcess/API/Cocoa/WKWebView.mm:
(isGreaterInDevicePixels):
(-[WKWebView _scrollViewIsRubberBanding]):
(-[WKWebView _updateVisibleContentRects]):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceWebKit2ChangeLog">trunk/Source/WebKit2/ChangeLog</a></li>
<li><a href="#trunkSourceWebKit2UIProcessAPICocoaWKWebViewmm">trunk/Source/WebKit2/UIProcess/API/Cocoa/WKWebView.mm</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceWebKit2ChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebKit2/ChangeLog (185575 => 185576)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebKit2/ChangeLog 2015-06-16 01:57:51 UTC (rev 185575)
+++ trunk/Source/WebKit2/ChangeLog 2015-06-16 02:10:58 UTC (rev 185576)
</span><span class="lines">@@ -1,3 +1,25 @@
</span><ins>+2015-06-15 Simon Fraser <simon.fraser@apple.com>
+
+ [iOS WK2] position:fixed elements sometimes truncated on scroll view bouncing
+ https://bugs.webkit.org/show_bug.cgi?id=146000
+ rdar://problem/19448439
+
+ Reviewed by Benjamin Poulain.
+
+ When in the middle of a rubber-band (UIScrollView bounce), we could send a bad
+ fixed position rect down to WebCore, causing 100% height elements to get laid out
+ at the wrong height, possible too short. This occurred when -_updateVisibleContentRects
+ said we were in a stable state, but the rubber-band offset caused WebPageProxy::computeCustomFixedPositionRect()
+ to compute a bad rect via constrainedUnobscuredRect.intersect(documentRect).
+
+ Fix by not claiming to be in a stable state during rubber-banding. Added _scrollViewIsRubberBanding
+ to compute that, taking care with floating point comparisons for 3x devices.
+
+ * UIProcess/API/Cocoa/WKWebView.mm:
+ (isGreaterInDevicePixels):
+ (-[WKWebView _scrollViewIsRubberBanding]):
+ (-[WKWebView _updateVisibleContentRects]):
+
</ins><span class="cx"> 2015-06-15 Ryuan Choi <ryuan.choi@navercorp.com>
</span><span class="cx">
</span><span class="cx"> Fix build break when ENABLE_SECCOMP_FILTERS is ON
</span></span></pre></div>
<a id="trunkSourceWebKit2UIProcessAPICocoaWKWebViewmm"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebKit2/UIProcess/API/Cocoa/WKWebView.mm (185575 => 185576)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebKit2/UIProcess/API/Cocoa/WKWebView.mm 2015-06-16 01:57:51 UTC (rev 185575)
+++ trunk/Source/WebKit2/UIProcess/API/Cocoa/WKWebView.mm 2015-06-16 02:10:58 UTC (rev 185576)
</span><span class="lines">@@ -689,6 +689,12 @@
</span><span class="cx"> return CGFloor(input * deviceScaleFactor) / deviceScaleFactor;
</span><span class="cx"> }
</span><span class="cx">
</span><ins>+static inline bool pointsEqualInDevicePixels(CGPoint a, CGPoint b, float deviceScaleFactor)
+{
+ return fabs(a.x * deviceScaleFactor - b.x * deviceScaleFactor) < std::numeric_limits<float>::epsilon()
+ && fabs(a.y * deviceScaleFactor - b.y * deviceScaleFactor) < std::numeric_limits<float>::epsilon();
+}
+
</ins><span class="cx"> static CGSize roundScrollViewContentSize(const WebKit::WebPageProxy& page, CGSize contentSize)
</span><span class="cx"> {
</span><span class="cx"> float deviceScaleFactor = page.deviceScaleFactor();
</span><span class="lines">@@ -1513,6 +1519,16 @@
</span><span class="cx"> return [self convertRect:unobscuredRect toView:self._currentContentView];
</span><span class="cx"> }
</span><span class="cx">
</span><ins>+// Ideally UIScrollView would expose this for us: <rdar://problem/21394567>.
+- (BOOL)_scrollViewIsRubberBanding
+{
+ float deviceScaleFactor = _page->deviceScaleFactor();
+
+ CGPoint contentOffset = [_scrollView contentOffset];
+ CGPoint boundedOffset = contentOffsetBoundedInValidRange(_scrollView.get(), contentOffset);
+ return !pointsEqualInDevicePixels(contentOffset, boundedOffset, deviceScaleFactor);
+}
+
</ins><span class="cx"> - (void)_updateVisibleContentRects
</span><span class="cx"> {
</span><span class="cx"> if (![self usesStandardContentView]) {
</span><span class="lines">@@ -1539,7 +1555,7 @@
</span><span class="cx">
</span><span class="cx"> CGFloat scaleFactor = contentZoomScale(self);
</span><span class="cx">
</span><del>- BOOL isStableState = !(_isChangingObscuredInsetsInteractively || [_scrollView isDragging] || [_scrollView isDecelerating] || [_scrollView isZooming] || [_scrollView isZoomBouncing] || [_scrollView _isAnimatingZoom] || [_scrollView _isScrollingToTop]);
</del><ins>+ BOOL isStableState = !(_isChangingObscuredInsetsInteractively || [_scrollView isDragging] || [_scrollView isDecelerating] || [_scrollView isZooming] || [_scrollView isZoomBouncing] || [_scrollView _isAnimatingZoom] || [_scrollView _isScrollingToTop] || [self _scrollViewIsRubberBanding]);
</ins><span class="cx">
</span><span class="cx"> // FIXME: this can be made static after we stop supporting iOS 8.x.
</span><span class="cx"> if (isStableState && [_scrollView respondsToSelector:@selector(_isInterruptingDeceleration)])
</span></span></pre>
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