1686462 - Color property displays differently for text vs border in Windows High Contrast Mode (WHC)

Status: NEW

(Core :: Disability Access APIs, defect)

Description

[stomme poes]

Attachment: Edge_Firefox_WHC_transparent_color.png

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.141 Safari/537.36

Steps to reproduce:

With Windows High Contrast running (Windows 10 in my case), view the test page (http://brothercake.com/Ref/color-transparent.html) in both Firefox (84) and Edge (87).
To ensure I was not hitting some launching bug in Firefox, I initialised WHC while FF was already running, then relaunched Firefox so it was launched with WHC already on.

Actual results:

Text with its color property set to transparent is invisible in Firefox while visible in Edge; border colours set with transparent remain visible.

Screenshot description: Edge 87 on the left, Firefox 84 on the right, with WHC running with one of the Black themes. In Edge, all the text and borders are visible, while in Firefox the text with the transparent color setting is invisible.

Expected results:

Firefox should follow the original (and current) behaviour of Windows High Contrast: the transparent color becomes replaced (as all other colors are) with the WHC theme for text or border colors. Text with a transparent color property should be visible.

For those asking "Why should it be visible?" One reason is, because this behaviour (in supporting Microsoft browsers) is the original behaviour, there are some accessibility CSS techniques which assume transparent colors are visible to WHC users. It is possibly more likely that text whose color is set to transparent is intended to be visible to WHC users than not around the web.

Note: I could not quite find this bug already filed, however
https://bugzilla.mozilla.org/show_bug.cgi?id=1105364 appears to complain that borders are still visible when border-color is set to transparent (they should remain visible, yes)
https://bugzilla.mozilla.org/show_bug.cgi?id=1536616 and https://bugzilla.mozilla.org/show_bug.cgi?id=779725 seem to touch on inputs or textareas having special circumstances, however the first of these is adding transparent to the field background. This (my) ticket does not involve any form fields nor are background-color properties being set.

Comment 1

[Andrew Overholt [:overholt]]

Asa, do you know if we're tracking content-related high contrast mode bugs with bug 1016556 or elsewhere?

Comment 2

[Asa Dotzler [:asa]]

I don't think we've got a metabug for content-specific issues. In this component it'll get triaged though.