Bug 141298

Summary: Scroll Snap Points animation sometimes fights user scroll gesture
Product: WebKit Reporter: Brent Fulgham <bfulgham>
Component: Layout and RenderingAssignee: Brent Fulgham <bfulgham>
Status: RESOLVED FIXED    
Severity: Normal CC: bfulgham, webkit-bug-importer
Priority: P2 Keywords: InRadar
Version: 528+ (Nightly build)   
Hardware: Mac   
OS: All   
Attachments:
Description Flags
Snap Point Example none

Description Brent Fulgham 2015-02-05 11:22:46 PST
Created attachment 246115 [details]
Snap Point Example

Using the attached test document, I sometimes find WebKit fighting with my scroll motion if a snap point animation starts, and I then attempt to start a manual scroll.

It seems like the animation is not being turned off when new user input is encountered.
Comment 1 Brent Fulgham 2015-02-05 11:59:50 PST
Manual Test:

1. Load the attached snap point example.
2. Partially scroll a view, so that the snap scroll kicks in and WebKit tries to slide the view back to the specified snap point.
3. While the snap point animation is running, begin a new scroll gesture to scroll the view.

Result:
Currently, you get jittering as the snap animation fights with the scrolling gesture.
Comment 2 Radar WebKit Bug Importer 2015-02-05 12:00:35 PST
<rdar://problem/19733626>
Comment 3 Brent Fulgham 2015-03-04 10:53:57 PST
This problem was corrected during other snap-point work.

The underlying problem was that certain wheel event states were not properly handled by the scroll snap animator logic. This caused the snap animation to continue to run even when the user began certain kinds of wheel gestures.

This is now resolved.