1686800 - Black flash software webrender (d3d11 compositor) on Windows 10

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, defect, P3)

Description

[Jeff Muizelaar [:jrmuizel]]

With software webrender enabled I get a black flash in-between the skeleton UI showing up and the real UI showing up.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

Bugbug thinks this bug should belong to this component, but please revert this change in case of error.

Comment 2

[Jeff Muizelaar [:jrmuizel]]

This happens without the skeleton UI. The skeleton UI just makes it more noticeable.

Comment 3

[Jeff Muizelaar [:jrmuizel]]

To summarize:
HW-WR: no flash
SW-WR-d3d11: black flash
d3d11: no flash
SW-WR: no flash

Sotaro or Matt any guesses as to the cause here?

Comment 4

[Sotaro Ikeda [:sotaro]]

Attachment: temporal patch - Clear with red

With the patch, Firefox had red flash. From it, no rendering seems to cause the black flash.

Comment 5

[Matt Woodrow (:mattwoodrow)]

Is this because RenderCompositorLayersSWGL calls BeginFrameForWindow, which includes a clear?

RenderCompositorSWGL only clears the buffer from StartCompositing/AllocateMappedBuffer.

If there's a frame where gecko calls RenderCompositor::BeginFrame, but WR doesn't call RenderCompositor::StartCompositor, then we'd clear but not draw any surfaces.

Comment 6

[Jim Mathies [:jimm]]

Possibly related to this - Bug 1697310 - about:support fails to render properly with software fallback

Comment 7

[Sotaro Ikeda [:sotaro]]

(In reply to Matt Woodrow (:mattwoodrow) from comment #5)

If there's a frame where gecko calls RenderCompositor::BeginFrame, but WR doesn't call RenderCompositor::StartCompositor, then we'd clear but not draw any surfaces.

I confirmed that it happened.

Comment 8

[Lee Salzman [:lsalzman]]

This seems like maybe a similar problem to bug 1696025 where we realized wr_renderer_update can result in composite_native->start_compositing->StartCompositing being called when not inside the scope of BeginFrame/EndFrame. Not quite the same, but in the same family of bugs maybe.

Comment 9

[Sotaro Ikeda [:sotaro]]

Attachment: Bug 1686800 - Call mCompositor->EndFrame() only when StartCompositing() is called

Comment 10

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/200f23c57336
Call mCompositor->EndFrame() only when StartCompositing() is called r=lsalzman

Comment 11

[Dorel Luca [:dluca]]

https://hg.mozilla.org/mozilla-central/rev/200f23c57336