1731052 - Scrollbars no longer have contrast on many sites with privacy.resistFingerprinting enabled.

Status: VERIFIED FIXED

(Core :: Widget: Gtk, defect)

Description

[Kestrel]

Attachment: Invisible scrollbar thumb

STR:

1. Set privacy.resistFingerprinting = true on Ubuntu 21.04.
2. Visit https://duckduckgo.com (light theme).

The scrollbar thumb is all white with no contrast against the background. When the site uses dark theme the scrollbar thumb is visible.

Regression window:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=8c9e9d61fc322fad479d14e993990102ecaedae8&tochange=13b542ebd7390ed8dc9029ecb80fad41a3262b31

Regressed by Bug 1730603.

Comment 1

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1731052 - Consider whether the color is CSS accessible to decide whether to use standins in nsNativeBasicTheme. r=mstange

We need to use standins for CSS-accesible colors in high contrast mode
(when appropriate) so that the CSS color matches the one in forms.css.

But this is not needed for e.g. scrollbar colors, which are not
CSS-accessible. So shuffle around the checks so that we account for
that as we should.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/6f52184495c0
Consider whether the color is CSS accessible to decide whether to use standins in nsNativeBasicTheme. r=mstange

Comment 3

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/6f52184495c0

Comment 4

[Ciprian Georgiu, Desktop QA]

I've reproduced this issue on an affected Nighty build (2021-09-16), on Win 11.

The issue is verified as fixed across platforms: Win 11, macOS 11 and Ubuntu 18.04 x64.