Firefox 89, WebRender, KDE Plasma and XRender

[Graham Perrin]

Please

Where about:support shows WebRender for compositing, is there any 
benefit to setting preferences such as the two below?

gfx.webrender.all true

gfx.webrender.enabled true

(Both are false, by default, in my Firefox 89.0.2.)

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In compositor preferences for KDE Plasma, my rendering backend is XRender.

(If I choose OpenGL 2.0 or 3.1, panels lose transparency.)

Does XRender in any way negate the benefits of WebRender?