Overview: If a WebView is partially clipped by its superview, even by 1 pixel, then a strange mouse-dragging behavior can result: when you drag the mouse (for example, to select some text), the WebView automatically scrolls downward slowly. This does not occur if the WebView is not clipped by its superview. Steps to Reproduce: 1. Unzip, open, build, and run the attached Sample Xcode project WebViewAutoscroll 2. Enter http://webkit.org/ into both the left and right text fields to load the page in both WebViews. 3. Click and drag the mouse to try to select some text in the first line of the first paragraph, "WebKit is an open..." Actual Results: The WebView slowly autoscrolls downward. Expected Results: The WebView doesn't autoscroll. Build Date & Platform: git commit de240fc8d016a25d9f4b05f65195414375159b3c, corresponding to svn r47855 Additional Builds and Platforms: Also occurs with stock WebKit in Mac OS X 10.5.8 Build 9L30 Additional Information: I've attached a sample Xcode project WebViewAutoscroll that demonstrates the bug. The only difference between the two WebViews is that the y-origin of the WebView on the left is set 1 pixel higher than the y-origin of the WebView on the right, so that the WebView on the left is clipped by its superview. When you build the project, you can see the CompileXIB warning "This view is clipped by its superview." The autoscrolling bug occurs with the left WebView but not with the right WebView.
Created attachment 38746 [details] Sample Xcode project