1525775 - Implement LookAndFeel::eIntID_SystemUsesDarkTheme

Status: RESOLVED FIXED

(Core :: Widget: Gtk, enhancement, P3)

Description

[Mats Palmgren (inactive)]

Over in bug 1494034 we're adding support for the CSS 'prefers-color-scheme'
media query. The platform info to support that comes from
"LookAndFeel::GetInt(LookAndFeel::eIntID_SystemUsesDarkTheme, 0)"
which appears to be implemented for OSX and Windows, but not GTK:
https://searchfox.org/mozilla-central/search?q=eIntID_SystemUsesDarkTheme

Does GTK have an API to answer if the current theme is "light" or "dark"?
If not, can we synthesize an answer based on some fg/bg colors?

Comment 1

[Cameron McCormack (:heycam)]

(In reply to Mats Palmgren (:mats) from comment #0)

Does GTK have an API to answer if the current theme is "light" or "dark"?
If not, can we synthesize an answer based on some fg/bg colors?

This sounds like a reasonable thing to do if there's no reliable way to know if the theme is dark or light.

Comment 2

[Taylor Hunt]

Bug #1461538 has some prior art on GTK dark themes, even if it’s not been going well.

Comment 3

[Mats Palmgren (inactive)]

This seems to work for me locally at least:
https://treeherder.mozilla.org/#/jobs?repo=try&revision=f6d56f8d470711dc1df9d4015f9897beb6fcd2f8

Comment 4

[Mats Palmgren (inactive)]

Attachment: fix

Comment 5

[Cameron McCormack (:heycam)]

Comment on attachment 9044464 [details] [diff] [review]
fix

Review of attachment 9044464 [details] [diff] [review]:
-----------------------------------------------------------------

This looks OK.  Since it's Gtk related I'd like to get Karl's sign off.

Comment 6

[Karl Tomlinson (:karlt)]

Comment on attachment 9044464 [details] [diff] [review]
fix

>+      // colors instead, by converting them to HSV and comparing the V part.

>+        uint16_t hue, sat, fg_v, bg_v;
>+        uint8_t alpha;
>+        NS_RGB2HSV(fg, hue, sat, fg_v, alpha);
>+        NS_RGB2HSV(bg, hue, sat, bg_v, alpha);
>+        aResult = bg_v < fg_v ? 1 : 0;

NS_GetLuminosity() provides a better indication of lightness or darkness than V = max(R,G,B) and is cheaper to compute, uses saner types, and involves fewer parameters than NS_RGB2HSV, so please use that, assuming there is not a compelling reason to use V.

Comment 7

[Mats Palmgren (inactive)]

OK, thanks.

Comment 8

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/133509097b7c
[css-mediaqueries] Synthesize a value for eIntID_SystemUsesDarkTheme to determine if GTK are using a light or dark theme.  r=heycam,karlt

Comment 9

[Narcis Beleuzu [:NarcisB]]

Backed out for dt failures on browser_webconsole_sidebar_scroll.js

Backout link: https://hg.mozilla.org/integration/mozilla-inbound/rev/659c7fae6ae49dc00e950a6755b7f724bcb9084e
Push link:https://treeherder.mozilla.org/#/jobs?repo=mozilla-inbound&resultStatus=testfailed%2Cbusted%2Cexception%2Crunnable&selectedJob=229063893&revision=e919946fd91306287e4a6197c52a77b6361676ce
Log link: https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=229063893&repo=mozilla-inbound&lineNumber=4268

Comment 10

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/738bb0805a9c
[css-mediaqueries] Synthesize a value for eIntID_SystemUsesDarkTheme to determine if GTK are using a light or dark theme.  r=heycam,karlt

Comment 11

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/738bb0805a9c