1439327 - [macOS] mix-blend-mode breaks rendering

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, defect, P1)

Description

[Alex]

In the 2018-02-18 nightly, trying to view a page using mix-blend-mode causes the UI to stop updating, and a error is emitted in the terminal.

Failed to link shader program: brush_mix_blend
WARNING: Output of vertex shader 'vLocalBounds' not read by fragment shader
ERROR: Input of fragment shader 'vUv' not written by vertex shader

 Failed to render: Shader(Link("brush_mix_blend", "WARNING: Output of vertex shader \'vLocalBounds\' not read by fragment shader\nERROR: Input of fragment shader \'vUv\' not written by vertex shader\n"))
[GFX1-]: wr_renderer_render: Shader(Link("brush_mix_blend", "WARNING: Output of vertex shader \'vLocalBounds\' not read by fragment shader\nERROR: Input of fragment shader \'vUv\' not written by vertex shader\n"))
[GFX1-]: Compositors might be mixed (5,2)

I could reliably reproduce it with the linked MDN article, clicking any of the multiply/hard-light/difference buttons in the first demo box caused it.

Cool side effect, if you full-screen the window and restore it, it goes entirely black save for the titlebar, and breaks vibrancy effects in other programs on top of it.

Comment 1

[Glenn Watson [:gw]]

This is likely to be an specific to a particular OS / driver version and GPU. Could you provide details of which version of OSX you are using and what model mac it is running on?

Comment 2

[Glenn Watson [:gw]]

Ah, I believe this will be resolved when the next WR update lands in Gecko.

This patch in WR removes the unused vUv interpolator from brush_mix_blend.glsl, which may explain why I cannot reproduce the problem locally.

https://github.com/servo/webrender/commit/3a17a77f48d9285fef5ee33f365c774b6d9c940c#diff-ca8941e141829862b8c0dcd25d49b25a