1720256 - 1-pixel gaps in multicolored glyphs with WebRender

Status: NEW

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

Description

[dong.james.sept14]

Attachment: Comparison of text rendering with/without WebRender enabled.

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Safari/537.36

Steps to reproduce:

Tested in clean profile, on Windows 10 build 19041.1083. My graphics card is Radeon RX 580 8GB.

1. Ensure zoom level is set to 100%.
2. Visit https://gankra.github.io/blah/text-hates-you/#style-can-change-mid-ligature

Actual results:

There is a 1-pixel gap in the colored glyph for न्हृे.

Expected results:

There is no gap. I have verified that the issue does not happen when WebRender is disabled. The issue appears and disappears depending on the zoom level.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

The Bugbug bot thinks this bug should belong to the 'Core::Graphics: WebRender' component, and is moving the bug to that component. Please revert this change in case you think the bot is wrong.

Comment 2

[Alice0775 White]

I can reproduce the issue in Nightly92.0a1 Windows10.

Comment 3

[Alice0775 White]

Regression window:
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=dfb15917c057f17e5143f7d7c6e1972ba53efc49&tochange=ce1d9b338bda9b21873f765faab05220727f2fa8

Suspect: Bug 1403261

Comment 4

[Jim Mathies [:jimm]]

Hey Lee, any idea where the issue is here?

Comment 5

[Jonathan Kew [:jfkthame]]

Attachment: Example of the issue on macOS, 170% scaling on a low-dpi display

I can also reproduce this on macOS; it's not specific to rendering on Windows.