1783145 - CSS "overline" text-decoration sometimes disappear in reduced size text.

Status: NEW

(Core :: Layout: Text and Fonts, defect)

Description

[techmanager]

Attachment: Firefox Helvetica sans-serif overline issue 1.png

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:103.0) Gecko/20100101 Firefox/103.0

Steps to reproduce:

• Open web page at https://fr.wikipedia.org/wiki/Transistor-Transistor_logic
• Read the sentence "Par exemple, pour trois entrées logiques A, B et C produisant l'état de la sortie logique Y, le transistor de liaison réalise d'abord l'opération X = A.B.C, puis le transistor d'amplification réalise l'opération Y = X = A.B.C."

My configuration:
Firefox 103.0.1 / macOS 10.14.6
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:103.0) Gecko/20100101 Firefox/103.0

Actual results:

At the end of the sentence, in "Y = X = A.B.C":

• the "X" appear with no bar over the text
• the bar over "A.B.C" is cropped.

Expected results:

The text "Y = X = A.B.C" should appear with a bar over "X" and "A.B.C".

The CSS attributes of this text are:

• text-decoration: overline;
• font-family: sans-serif; (actually Helvetica)
• initial font-size: 16px;
• cooked font-size: calc(1em * 0.875);
  Using these attributes, I can reproduce the issue over most of the capital characters.
  The issue is still present with:
• font-size: calc(1em * 0.890);
• font-size: calc(1em * 0.960);
• font-size: calc(1em * 0.970);
  The issue disappear with:
• font-size: calc(1em * 0.895);
• font-size: calc(1em * 0.930);
• font-size: calc(1em * 0.960);
• font-size: calc(1em * 0.975);
  The issue disappear when I zoom in the web page.

Comment 1

[techmanager]

Attachment: Firefox Helvetica sans-serif overline issue 2.png

Comment 2

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

The Bugbug bot thinks this bug should belong to the 'Core::Layout: Text and Fonts' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 3

[techmanager]

Attachment: Firefox Helvetica sans-serif overline issue 3.png

The issue can be reproduced using simple CSS text-size attributes less than 16px.

Comment 4

[techmanager]

^ font-size attributes -- sorry

Comment 5

[David Shin[:dshin]]

Attachment: Minimum reproducible test case

I don't have Helvetica, but I can see overline overlapping even at 16px with what my system considers the closes match.

Comment 6

[techmanager]

I am currently using an up-to-date version of Firefox ESR (115.11.0esr) and this issue is still not fixed.
The issue is not visible anymore on the Wikipedia as the page has been modified with a workaround, but David Shin's "minimum reproducible test case" — https://bugzilla.mozilla.org/attachment.cgi?id=9288824 — still shows the problem.