Colors on ANGLE are darker than expected

[bigfarts]

Description Colors on ANGLE are darker than expected, likely because of some sRGB color issue.

Repro steps https://gist.github.com/bigfarts/3f051479c2c786d91f0b4e618d346dbc

This is just a basic drawing demo, which emits fragment color vec4<f32>(0.5, 0.2, 0.3, 1.0).

Expected vs observed behavior Vulkan:

Metal:

ANGLE:

Extra materials The swapchain format selected on all of Vulkan, Metal, and ANGLE are Bgra8UnormSrgb, but it looks like ANGLE treats the input color as sRGB but Vulkan and Metal treat it as linear.

Platform OS: Windows 11 wgpu version: v0.13.2 ANGLE version: https://github.com/google/gfbuild-angle/releases/tag/github%2Fgoogle%2Fgfbuild-angle%2Ff810e998993290f049bbdad4fae975e4867100ad

[bigfarts]

Replacing the EGL code with the WebGL code gets the colors right, but I don't know if it's a good fix: https://gist.github.com/bigfarts/b1f3759e61afb62b41c0a88e2e1602d2

[cwfitzgerald]

I think this should not be an issue anymore.