Changeset 170463 in webkit

Timestamp:

Jun 25, 2014 9:15:52 PM (10 years ago)

Author:

Simon Fraser

Message:

[iOS WK2] Page jumps when rubber-banding on azuremagazine.com
​https://bugs.webkit.org/show_bug.cgi?id=134238
<rdar://problem/16918228>

Reviewed by Benjamin Poulain.

If the scroll view is in the process of rubber-banding when -setContentSize: is called,
it clamps the scroll offsets between zero and the max value, which visibly interrupts the
rubberband. This can easily happen now that we continually send scroll events to the page
on scrolling, especially when pages like azuremagazine.com do fake sticky by toggling
in-flow elements into position:fixed.

Fix by computing the amount of rubber-band before calling -setContentSize:, and then
restoring the contentOffset with the same amount of rubber-band even when the content size
is different, for top/left rubberbands.

• UIProcess/API/Cocoa/WKWebView.mm:

(-[WKWebView _didCommitLayerTree:WebKit::]):

• UIProcess/ios/WKScrollView.h:
• UIProcess/ios/WKScrollView.mm:

(-[WKScrollView _currentTopLeftRubberbandAmount]):
(-[WKScrollView _restoreContentOffsetWithRubberbandAmount:]):
(-[WKScrollView _setContentSizePreservingContentOffsetDuringRubberband:]):

Location:

trunk/Source/WebKit2

Files:

• ChangeLog (modified) (1 diff)
• UIProcess/API/Cocoa/WKWebView.mm (modified) (1 diff)
• UIProcess/ios/WKScrollView.h (modified) (1 diff)
• UIProcess/ios/WKScrollView.mm (modified) (1 diff)

trunk/Source/WebKit2/ChangeLog

@@ +1 @@
+2014-06-25  Simon Fraser  <simon.fraser@apple.com>
+
+        [iOS WK2] Page jumps when rubber-banding on azuremagazine.com 
+        https://bugs.webkit.org/show_bug.cgi?id=134238
+        <rdar://problem/16918228>
+
+        Reviewed by Benjamin Poulain.
+        
+        If the scroll view is in the process of rubber-banding when -setContentSize: is called,
+        it clamps the scroll offsets between zero and the max value, which visibly interrupts the
+        rubberband. This can easily happen now that we continually send scroll events to the page
+        on scrolling, especially when pages like azuremagazine.com do fake sticky by toggling
+        in-flow elements into position:fixed.
+        
+        Fix by computing the amount of rubber-band before calling -setContentSize:, and then
+        restoring the contentOffset with the same amount of rubber-band even when the content size
+        is different, for top/left rubberbands.
+        
+        * UIProcess/API/Cocoa/WKWebView.mm:
+        (-[WKWebView _didCommitLayerTree:WebKit::]):
+        * UIProcess/ios/WKScrollView.h:
+        * UIProcess/ios/WKScrollView.mm:
+        (-[WKScrollView _currentTopLeftRubberbandAmount]):
+        (-[WKScrollView _restoreContentOffsetWithRubberbandAmount:]):
+        (-[WKScrollView _setContentSizePreservingContentOffsetDuringRubberband:]):
+
 2014-06-25  Simon Fraser  <simon.fraser@apple.com>
 

trunk/Source/WebKit2/UIProcess/API/Cocoa/WKWebView.mm

@@ -775 +775 @@
     }
 
-    [_scrollView setContentSize:roundScrollViewContentSize(*_page, [_contentView frame].size)];
+    CGSize newContentSize = roundScrollViewContentSize(*_page, [_contentView frame].size);
+    [_scrollView _setContentSizePreservingContentOffsetDuringRubberband:newContentSize];
+
     [_scrollView setMinimumZoomScale:layerTreeTransaction.minimumScaleFactor()];
     [_scrollView setMaximumZoomScale:layerTreeTransaction.maximumScaleFactor()];

trunk/Source/WebKit2/UIProcess/ios/WKScrollView.h

@@ -34 +34 @@
 @property (nonatomic, assign) WKWebView <UIScrollViewDelegate> *internalDelegate;
 
+- (void)_setContentSizePreservingContentOffsetDuringRubberband:(CGSize)contentSize;
+
 @end
 

trunk/Source/WebKit2/UIProcess/ios/WKScrollView.mm

@@ -199 +199 @@
 }
 
+// Fetch top/left rubberband amounts (as negative values).
+- (CGSize)_currentTopLeftRubberbandAmount
+{
+    UIEdgeInsets edgeInsets = [self contentInset];
+
+    CGSize rubberbandAmount = CGSizeZero;
+
+    CGPoint contentOffset = [self contentOffset];
+    if (contentOffset.x < -edgeInsets.left)
+        rubberbandAmount.width = std::min<CGFloat>(contentOffset.x + -edgeInsets.left, 0);
+
+    if (contentOffset.y < -edgeInsets.top)
+        rubberbandAmount.height = std::min<CGFloat>(contentOffset.y + edgeInsets.top, 0);
+    
+    return rubberbandAmount;
+}
+
+- (void)_restoreContentOffsetWithRubberbandAmount:(CGSize)rubberbandAmount
+{
+    UIEdgeInsets edgeInsets = [self contentInset];
+    CGPoint adjustedOffset = [self contentOffset];
+
+    if (rubberbandAmount.width < 0)
+        adjustedOffset.x = -edgeInsets.left + rubberbandAmount.width;
+
+    if (rubberbandAmount.height < 0)
+        adjustedOffset.y = -edgeInsets.top + rubberbandAmount.height;
+
+    [self setContentOffset:adjustedOffset];
+}
+
+- (void)_setContentSizePreservingContentOffsetDuringRubberband:(CGSize)contentSize
+{
+    CGSize currentContentSize = [self contentSize];
+
+    if (CGSizeEqualToSize(currentContentSize, CGSizeZero) || CGSizeEqualToSize(currentContentSize, contentSize) || self.zoomScale < self.minimumZoomScale) {
+        [self setContentSize:contentSize];
+        return;
+    }
+
+    CGSize rubberbandAmount = [self _currentTopLeftRubberbandAmount];
+
+    [self setContentSize:contentSize];
+
+    if (!CGSizeEqualToSize(rubberbandAmount, CGSizeZero))
+        [self _restoreContentOffsetWithRubberbandAmount:rubberbandAmount];
+}
+
 @end