1473352 - Send DidComposite messages for pipelines that weren't actually rendered

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, enhancement, P2)

Description

[Kartikaya Gupta (email:[e-mail])]

Spinoff from https://bugzilla.mozilla.org/show_bug.cgi?id=1471962#c8, copying that comment here:

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So it looks like with layers, we send a DidComposite for content-process layers even if those layers are not attached to the parent process layers. i.e. say we create a new tab, and we create the associated RenderFrameParent in the UI process. That RenderFrameParent doesn't actually get painted right away; some code (I presume the front-end) keeps it deactivated somehow until it knows that the content process layers have been painted via a MozAfterPaint, and then it activates the RenderFrameParent.

With WR, that MozAfterPaint doesn't happen because, well, the display list wasn't rendered and so the PipelineInfo doesn't contain the epoch for the content process pipeline. After 100ms that timer [1] expires, fires the MozAfterPaint, and then that allows the front-end to activate the RenderFrameParent. If I increase the timer from 100ms to 1000ms the exact same thing happens - it takes 1000ms before the MozAfterPaint fires and unblocks the painting.

So I think for consistency with layers we need to make it so that even if a content process display list isn't attached to the parent process we need to send a MozAfterPaint for it.
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[1] https://searchfox.org/mozilla-central/rev/97d488a17a848ce3bebbfc83dc916cf20b88451c/layout/base/nsPresContext.cpp#3303

Comment 1

[Kartikaya Gupta (email:[e-mail])]

This is fixed now.