From github: https://github.com/mozilla-mobile/fenix/issues/20193.

Steps to reproduce

set gfx.webrender.software to true and restart your browser. now try to open any website

Expected behavior

the background color when loading the page should be dark

Actual behavior

white flash appear

Device information

• Device vendor / model and Android version: Samsung/Android 11
• Firefox for Android version: Nightly v.91

Change performed by the Move to Bugzilla add-on.

I

Fenix makes use of the default clear color by setting it to a dark
color when the dark theme is enabled to avoid white flashes while
pages are loading. In bug 1663732 we hooked this functionality up to
webrender, however, it was only used by the draw compositor. Now with
software webrender on Android, we sometimes use
RenderCompositorLayersSWGL rather than the draw compositor, and users
are therefore experiencing white flashes during page loads.

This adds a clear_color argument to StartCompositing(), which
RenderCompositorLayersSWGL uses to set the CompositorOGL's clear
color. This patch also makes Renderer::clear_color not an Option
type, as we only ever used it in Some form, and that simplifies the
FFI.

Sorry, Sotaro. I started working on this bug this morning but forgot to assign it to myself. I only noticed you had assigned it to yourself after I uploaded the patch!

No problem:) Thank for taking the bug.

Backed out for causing build bustages

Backout link: https://hg.mozilla.org/integration/autoland/rev/54b6ae5e9f7d1760eff76346b3b82bdc37bddfae

Push with failures

Failure log

Oh, whoops. I forgot to update the examples for changing the Option<ColorF> to ColorF

https://hg.mozilla.org/mozilla-central/rev/4054c870a437