Closed Bug 1134129 Opened 5 years ago Closed 5 years ago

Without APZ, scrollgrab element and its child scroll at the same time


(Core :: Panning and Zooming, defect)

Not set





(Reporter: paul, Unassigned)



With APZC, the scrollgrab element scrolls first, then its child. Without APZC, both scroll at the same time.
Botond, any idea how to solve that? I'd be happy to give it a try if you're busy (but I have no idea where to look).
Flags: needinfo?(botond)
Erm, I pressed <enter> too quickly there. Let me try again:

The behaviour that scrollgrab affects - basically, the initial target of user input that causes scrolling, and how scroll is handed off from there when the initial target is scrolled to its maximum extent - is implemented separately for synchronous and asynchronous (APZ) scrolling.

Scrollgrab has only been implemented for APZ.

If you need scrollgrab behaviour on a platform that doesn't use APZ, the options are basically:

  (1) Implement scrollgrab behaviour for synchronous scrolling.

  (2) Wait for the platforms in question to switch to APZ.

We're actively working on (2). We have no plans to do (1). 

If you'd like to do (1) yourself, the relevant code is in EventStateManager. I don't know much about it, but I can probably point you to some relevant sections of it, and/or point you to people who know it better.
Based on the discussion I think this is a wontfix? If you plan on doing (1) please move this into Core::Layout or a more appropriate component.
Closed: 5 years ago
Resolution: --- → WONTFIX
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