Bug 188894

Summary: [Cocoa] First scroll gesture in pinned, non-rubber-banding WKWebView may fail to initiate back/forward swipe
Product: WebKit Reporter: mitz
Component: WebKit2Assignee: mitz
Status: RESOLVED FIXED    
Severity: Normal CC: simon.fraser, thorton
Priority: P2 Keywords: InRadar
Version: Other   
Hardware: Unspecified   
OS: Unspecified   
Attachments:
Description Flags
Set the rubber-band state from the event dispatcher thread thorton: review+

Description mitz 2018-08-23 11:33:28 PDT 
Sometimes the first swipe gesture in a WKWebView would fail to initiate a back/forward swipe despite the view being pinned to the edge and non-rubber-banding. This happens because of a race condition in EventDispatcher::wheelEvent, where setting the rubber-band state is dispatched to the scrolling thread, whereas querying the rubber-banding state happens immediately right after that on the event dispatcher thread, under tryToHandleWheelEvent().
Comment 1 mitz 2018-08-23 11:38:42 PDT 
<rdar://problem/43651434>
Comment 2 mitz 2018-08-23 11:42:37 PDT 
Created attachment 347941 [details]
Set the rubber-band state from the event dispatcher thread
Comment 3 mitz 2018-08-23 12:51:40 PDT 
Fixed in <https://trac.webkit.org/r235236>.