2067555 - Bottom of text in UI slightly cut

Status: RESOLVED FIXED

(Core :: Graphics: Text, defect)

Description

[Merci chao]

Attachment: 2026_08_30_12_12_44.mp4

The bottom of text in certain UI elements is slightly cut off. For example, in the bookmarks toolbar and the hamburger menu, the descenders of letters such as “g” are clipped.

Comment 1

[Alice0775 White]

Regression window:
https://hg-edge.mozilla.org/integration/autoland/pushloghtml?fromchange=e1737460dd209523c9591509f1c244f6eb6d59f9&tochange=79a3125a8baae1d42cc2b98eedb448472eb3bc42

Disable HWA fix the issue on Windows11.

Comment 2

[BugBot [:suhaib / :marco]]

Set release status flags based on info from the regressing bug 2050692

:gw, since you are the author of the regressor, bug 2050692, could you take a look? Also, could you set the severity field?

For more information, please visit BugBot documentation.

Comment 3

[Glenn Watson [:gw]]

Attachment: Bug 2067555 - Quantise a text run's clip on the axes its glyphs are snapped on

A glyph pen is sub-pixel positioned on one axis and rounded to a whole device
pixel on the other. Bug 2050692 left the clip exact on both, but that is only
needed on the sub-pixel axis: elsewhere an exact clip disagrees with the grid the
glyphs landed on, and since the shader clamps the glyph quad with no coverage
term, a clip edge falling mid-row drops that row of ink outright.

Nearest is the rounding that works: the line box is ascent + descent, so the clip
and the pen are both round(box offset + an integer) and stay flush at every
phase. Bug 2055145 rounded outward instead, which spills a pixel whenever the ink
does not round up (bug 2065629).

So derive the axes from the font's SubpixelDirection, mirroring the snap_bias
table it already drives; local-raster runs snap in raster space, so leave them.
The snap is applied in request_resources and stored on the run's scratch, so
culling still sees the unsnapped clip.

Exact and nearest differ only at the .5 tie, which is where the reftest puts it.

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/ae6e50e39a18
https://hg.mozilla.org/integration/autoland/rev/85dfd4ebc2d0
Quantise a text run's clip on the axes its glyphs are snapped on r=gfx-reviewers,nical

Comment 5

[Serban Stanca [:SerbanS]]

https://hg.mozilla.org/mozilla-central/rev/85dfd4ebc2d0

Comment 6

[BugBot [:suhaib / :marco]]

The patch landed in nightly and beta is affected.
:gw, is this bug important enough to require an uplift?

• If yes, please nominate the patch for beta approval.
  • See https://wiki.mozilla.org/Release_Management/Requesting_an_Uplift for documentation on how to request an uplift.
• If no, please set status-firefox156 to wontfix.

For more information, please visit BugBot documentation.