802478 - Smooth scrolling causes plugins to bounce while scrolling

Status: RESOLVED INVALID

(Core :: Web Painting, defect)

Description

[IU]

Bug 198964 enabled smooth scrolling by default, resulting in bug 626245.  Bug 626245 fixed some issue that made the effect worse; however the original regression, due to bug 198964, remains.

Video demonstration is available here: http://youtu.be/fDH62trzUp4

Observe, in the video, how the lower left-hand corner of the plugin object extends beyond the gray background frame when the page is "bounce-scrolled."

Comment 1

[IU]

(In reply to IU from comment #0)
> ...when the page is "bounce-scrolled."

Or simply quickly scrolled up or down

Comment 2

[Virtual_ManPL [:Virtual] 🇵🇱 - (please needinfo? me - so I will see your comment/reply/question/etc.)]

Any ideas guys how to fixed it?

Pasting some info from bug #626245

(In reply to Robert O'Callahan (:roc) (Mozilla Corporation) from comment #88)
> Unfortunately it's not really possible to completely fix it for windowed
> plugins. We simply can't make the update of the window and the movement of
> plugin widgets perfectly visually atomic.
> 
> We could probably make it a little better by having some kind of callback
> from the layer manger when it's just about to copy its backbuffer to the
> window, and move the plugins at that moment. We'd have to do something to
> ensure the area exposed by the plugins was part of the area composited by
> the layer manager.

(In reply to Robert O'Callahan (:roc) (Mozilla Corporation) from comment #89)
> This would require some code restructuring because on Windows we'd have to
> issue BeginPaint during layer tree composition. We'd probably have to add a
> BeginPaint method to nsIWidget (no-op for all platforms but Windows), then
> call that method from the layer manager just before we start drawing to the
> window. On Mac that wouldn't work since we can't modify the widget hierarchy
> during the 'draw' callback, so we'd have to carry on moving the plugins in
> viewWillDraw/WillPaintWindow on Mac.

Comment 3

[Mats Palmgren (inactive)]

This is a minor problem, we'll get to it eventually.

Comment 4

[Mats Palmgren (inactive)]

We're in the process of removing support for plugins (bug 1677160), so I think this bug is irrelevant now.