1916589 - Add BrowsingContext flag to emulate forced-colors

Status: RESOLVED FIXED

(Core :: Layout, task)

Description

[Nicolas Chevobbe [:nchevobbe]]

This could then be used by DevTools to emulate forced-colors/HCM on a single page

Comment 1

[Eitan Isaacson [:eeejay]]

Anna will probably take this.

Comment 2

[Nicolas Chevobbe [:nchevobbe]]

Attachment: Bug 1916589 - Add forcedColorsOverride flag to BrowsingContext. r=emilio.

Comment 3

[Nicolas Chevobbe [:nchevobbe]]

In https://bugzilla.mozilla.org/show_bug.cgi?id=1591539#c2

The platform bits of this aren't too complicated, fwiw, happy to help / mentor.

Emilio, since you offered some mentoring, I'll gladly take it :)

I started a WIP patch (https://phabricator.services.mozilla.com/D221334), which is basically copying all the same bits we had in BrowsingContext for preferedColorSchemeOverride. Now I guess is a matter or where to use this new flag in the code to actually override the forced-colors media query

Comment 4

[Emilio Cobos Álvarez (:emilio)]

I left some comments. But basically, you need to store either the browsing-context flag or the resolved forced-colors value somewhere in the pres context (probably mMediaEmulationData for the former, and an enum for the later), then change this to honor it, and update it in UpdateBrowsingContextDependentData().

My suggestion would be to add the resolved value in the pres context which should be slightly cheaper when using it from style.

Comment 5

[Nicolas Chevobbe [:nchevobbe]]

(In reply to Emilio Cobos Álvarez (:emilio) from comment #4)

I left some comments. But basically, you need to store either the browsing-context flag or the resolved forced-colors value somewhere in the pres context (probably mMediaEmulationData for the former, and an enum for the later), then change this to honor it, and update it in UpdateBrowsingContextDependentData().

My suggestion would be to add the resolved value in the pres context which should be slightly cheaper when using it from style.

Thanks for the pointers Emilio!

Comment 6

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1916589 - Move forced-colors computation to nsPresContext. r=nchevobbe

Untested, but something like this is what I meant above.

Comment 7

[Nicolas Chevobbe [:nchevobbe]]

Not sure if you saw my comment on Phabricator, so putting a needinfo so it's visible:

looks like layout/style/test/test_dont_use_document_colors.html is failing with this patch: https://treeherder.mozilla.org/logviewer?job_id=474223582&repo=try&lineNumber=8796

Comment 8

[Emilio Cobos Álvarez (:emilio)]

Applying the patch to latest central doesn't cause the test to fail locally... Is it opt only somehow? Or something else?

Comment 9

[Nicolas Chevobbe [:nchevobbe]]

(In reply to Emilio Cobos Álvarez (:emilio) from comment #8)

Applying the patch to latest central doesn't cause the test to fail locally... Is it opt only somehow? Or something else?

It does fail for me locally, I don't have anything specific in my mozconfig. Do you want me to check something specific ?

Comment 10

[Nicolas Chevobbe [:nchevobbe]]

Let me pull the last version from phab to confirm that though

Comment 11

[Emilio Cobos Álvarez (:emilio)]

Hmm, I guess I'll try on macOS, but it works for me. I think I missed one place where I had to call UpdateForcedColors(), mind pulling the latest version and confirming it fixes it for you?

Comment 12

[Nicolas Chevobbe [:nchevobbe]]

(In reply to Emilio Cobos Álvarez (:emilio) from comment #11)

Hmm, I guess I'll try on macOS, but it works for me. I think I missed one place where I had to call UpdateForcedColors(), mind pulling the latest version and confirming it fixes it for you?

last version works fine 👍

Comment 13

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/4e1b664de4d8
Move forced-colors computation to nsPresContext. r=nchevobbe
https://hg.mozilla.org/integration/autoland/rev/2c735de75ad9
Add forcedColorsOverride flag to BrowsingContext. r=emilio.

Comment 14

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/4e1b664de4d8
https://hg.mozilla.org/mozilla-central/rev/2c735de75ad9