1633109 - svg underline issue with centered text

Status: NEW

(Core :: Layout: Text and Fonts, defect, P3)

Description

[mburo]

Attachment: testcase.zip contains a html file, a font, and two screenshots

User Agent: Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:75.0) Gecko/20100101 Firefox/75.0

Steps to reproduce:

unzip testcase.zip
firefox test.html
chrome test.html

Actual results:

An unexpected underline pattern is produced

Expected results:

Regular underlined text should be generated (compare with chrome output - attached). I included a font to show that this isn't a font issue.

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

[Robert Longson [:longsonr]]

Attachment: reporters testcase

Comment 3

[Robert Longson [:longsonr]]

Attachment: Chrome screenshot

Comment 4

[Robert Longson [:longsonr]]

Attachment: Firefox screenshot

Comment 5

[Robert Longson [:longsonr]]

Attachment: font

Comment 6

[Robert Longson [:longsonr]]

Attachment: reporters testcase

Comment 7

[Robert Longson [:longsonr]]

Seems fine on Mac. layout/text probably makes more sense for this.

Comment 8

[Jonathan Kew [:jfkthame]]

The issue reproduces for me on macOS too. (Note that the testcase attached to bugzilla fails to load the linked font, because the attachment fails a CORS check. So we get fallback to Times, where the issue isn't noticeable -- though if you look carefully, the underline is a bit closer to the text in the top example than the lower one, so the same issue does exist, just not sufficiently to hit the text and start skipping.)

So the root of the issue seems to be that when dominant-baseline is set to middle (or central), the text is shifted lower, but the underline does not shift along with it.

Comment 9

[Firefox Bug Husbandry Bot]

Because this bug's Severity has not been changed from the default since it was filed, and it's Priority is P3 (Backlog,) indicating it has been triaged, the bug's Severity is being updated to S3 (normal.)

Comment 10

[Jonathan Kew [:jfkthame]]

Attachment: testcase for various dominant-baseline values

Testcase that shows the issue with the dominant-baseline values middle, central, and mathematical (works on both macOS and Windows, at least; results on Linux will depend on the serif font available).

Comment 11

[Jonathan Kew [:jfkthame]]

Looks like the code we use to "recover the correct baseline" in nsTextFrame::GetTextDecorations is bogus for SVG text elements, where we don't really have vertical-align adjustments happening.

Comment 12

[Jonathan Kew [:jfkthame]]

Attachment: Bug 1633109 - Don't try to compensate for baseline adjustment (vertical-align) when getting decorations for SVG text. r=heycam

Comment 13

[Jonathan Kew [:jfkthame]]

As noted in phabricator, I think the main issue here is actually that we're mishandling dominant-baseline; filed bug 1638836 about that. When that is fixed we can revisit this and see if there's still a problem.

Comment 14

[Robert Longson [:longsonr]]

The patch in bug 1638836 fixes this too.