Bug 130474

Summary: REGRESSION(r156316): Scrollbar on a large document is broken
Product: WebKit Reporter: Ryosuke Niwa <rniwa>
Component: Layout and RenderingAssignee: Ryosuke Niwa <rniwa>
Status: RESOLVED FIXED    
Severity: Normal CC: andersca, bdakin, bfulgham, kling, sam, simon.fraser, webkit-bug-importer
Priority: P2 Keywords: InRadar, Regression
Version: 528+ (Nightly build)   
Hardware: Unspecified   
OS: Unspecified   
URL: http://www.whatwg.org/specs/web-apps/current-work/multipage/
Attachments:
Description Flags
Fixes the bug andersca: review+

Description Ryosuke Niwa 2014-03-19 14:15:57 PDT 
Reproduction steps
1. Go to http://www.whatwg.org/specs/web-apps/current-work/multipage/
2. Scroll all the way down to the bottom via wheel/trackpad
3. Scroll up so that the scollbar is above "Help" button via wheel/trackpad.
4. Try to drag the scrollbar.

Expected result:
Scrollbar moves to the direction I dragged

Actual result:
Scrollbar always moves downwards.
Comment 1 Radar WebKit Bug Importer 2014-03-19 14:16:39 PDT 
<rdar://problem/16371523>
Comment 2 Ryosuke Niwa 2014-03-19 14:29:48 PDT 
The problem appears that updateArrowPlacement is no longer exiting early in ToT:
http://trac.webkit.org/changeset/156316/trunk/Source/WebCore/platform/mac/ScrollbarThemeMac.mm

Since isScrollbarOverlayAPIAvailable() is always true, we should be returning there.
Comment 3 Ryosuke Niwa 2014-03-19 14:32:40 PDT 
Created attachment 227219 [details]
Fixes the bug
Comment 4 Ryosuke Niwa 2014-03-19 14:37:46 PDT 
Committed r165918: <http://trac.webkit.org/changeset/165918>