1593970 - If WebRender is enabled, all nonzero gfx.font_rendering.cleartype_params.cleartype_level values are rendered as 100

Status: RESOLVED FIXED

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

Description

[nyanpasu64]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:70.0) Gecko/20100101 Firefox/70.0

Steps to reproduce:

Edit about:config.

• Set gfx.webrender.enabled and gfx.webrender.all to true.
• Either set gfx.font_rendering.cleartype_params.cleartype_level to numbers between 0 and 100, or set cleartype_level to -1 and run cttune.exe and pick 50% subpixel coloration.

How do you select subpixel coloration in cttune.exe? On step (3 of 5), there are 3 selections. Left is 100% color, middle is 50% color, and right is 0% color.

Actual results:

• If cleartype_level is nonzero, fonts are rendered as if gfx.font_rendering.cleartype_params.cleartype_level is set to 100. If you zoom in on Firefox text, the colorful fringes are very saturated. (You can open Windows Magnifier by pressing Win +.)
• If cleartype_level is zero, fonts are rendered in grayscale.
• If cleartype_level is -1, the same bug occurs; picking 50% color in cttune.exe causes Firefox to render in 100% subpixel. Picking 100% or 0% color work as expected.

Expected results:

As I decrease gfx.font_rendering.cleartype_params.cleartype_level, the vibrancy/saturation of the colorful fringes decreases, converging to fully grayscale when I set it to 0.

If I turn off gfx.webrender.enabled and gfx.webrender.all and restart Firefox, then cleartype_level behaves as I expect, for both [0..100] and -1.

(this is the kind of bug most people wouldn't even notice, and no reasonable person would care about ;)

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

[Lee Salzman [:lsalzman]]

Attachment: Bug 1593970 - scale subpixel contribution based on ClearType level setting. r?jfkthame

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/d967ac6c56ae
scale subpixel contribution based on ClearType level setting. r=jfkthame

Comment 4

[Cosmin Sabou [:CosminS]]

https://hg.mozilla.org/mozilla-central/rev/d967ac6c56ae