1596050 - Text selection while Windows High Contrast is running becomes invisible in Firefox

Status: NEW

(Core :: Layout: Text and Fonts, defect, P1)

Description

[stomme poes]

Attachment: Firefox and Edge with Windows High Contrast enabled and multiple text blocks selected. Sections of text (which have the CSS ::selection property set) are shown to have no highlight in Firefox.

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.97 Safari/537.36

Steps to reproduce:

1. Turn on Windows High Contrast (Windows 10, 8, 7, XP, doesn't matter):
   On Windows, activate the High Contrast setting using the Alt+Shift+PrtScn shortcut, or access it via the Access Settings (Windows Key + U, or via Start Menu → Settings → Ease of Access). It does not matter which theme is chosen.
2. Open Firefox and view a web page which uses CSS ::selection properties to set a custom selection highlight. For example, https://www.smashingmagazine.com/2019/11/newspapers-teach-web-design
3. Select some text, either with the mouse or by using caret navigation (Shift+arrows).
4. Observe the selected text.
5. Perform the above steps in another browser which supports WHC (Edge, IE11).
6. Observe the selected text.

Actual results:

No selection highlight is seen in Firefox.
Selection highlight is seen in other WHC-supporting browsers (Edge, IE11), albeit with the WHC selection colours and not those of the site.

Expected results:

A selection highlight should be visible in Firefox.

Comment 1

[stomme poes]

Note: the URL visible in the screenshots does not have complete test results. I am waiting access back to my server.

Comment 2

[stomme poes]

A github bug which described this bug: https://github.com/csstools/sanitize.css/issues/173

Comment 3

[Jonathan Kew (:jfkthame)]

It looks like there's code in widget/windows to detect if High Contrast mode is on. Perhaps we should just be ignoring any CSS-specified ::selection colors in this case -- :Jamie, WDYT?

Comment 4

[Emilio Cobos Álvarez (:emilio)]

So, this should be happening already, due to the "ignored_when_colors_disabled" stuff. The issue in that case is that we'd end up with the inherited color, I guess, which is not what we want in this case.

So maybe we need a check for that before computing the ::selection style...

Comment 5

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1596050 - Centralize logic to ignore document colors. r=jfkthame

This was a follow-up from the backplate stuff which I requested but didn't
happen.

Comment 6

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1596050 - When ignoring document colors, ignore ::selection styles altogether. r=morgan

Depends on D53170

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/2a60597c2972
Centralize logic to ignore document colors. r=jfkthame

Comment 8

[Stefan Hindli [:stefan_hindli]]

https://hg.mozilla.org/mozilla-central/rev/2a60597c2972

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/6c09d8b07585
When ignoring document colors, ignore ::selection styles altogether. r=morgan

Comment 10

[Cristina Coroiu [:ccoroiu]]

Backed out changeset 6c09d8b07585 (bug 1596050) for reftest failures at layout/reftests/high-contrast/selection-001.html

Backout: https://hg.mozilla.org/integration/autoland/rev/13923424c3fc752201e23d13492190b2cec1efcd

Failure push: https://treeherder.mozilla.org/#/jobs?repo=autoland&revision=6c09d8b075850f2e86995106981c3d45379dc048

Failure log: https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=279136384&repo=autoland&lineNumber=10543

Comment 11

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/eab89fc5733a
When ignoring document colors, ignore ::selection styles altogether. r=morgan

Comment 12

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/eab89fc5733a