[FR]: determine prefers-color-scheme via desktop portal or override

[Acumane]

Description

obey desktop portal color-scheme or allow user to set prefers-color-scheme manually

Who's implementing?

• I'm willing to implement this feature myself

The problem

Helium shouldn't infer prefers-color-scheme from my GTK theme.

Currently, OsSettingsProviderGtk::PreferredColorScheme() measures GTK window background color luminance instead of obeying the org.freedesktop.appearance color-scheme value (same behavior as Chrome).

Possible solutions

imo desktop portal is the correct way to signal this but open to other options (e.g. firefox lets you set layout.css.prefers-color-scheme.content-override)

Additional context

No response

[Acumane]

Related to #535 depending on solution

[dumbmoron]

Currently, OsSettingsProviderGtk::PreferredColorScheme() measures GTK window background color luminance instead of obeying the org.freedesktop.appearance color-scheme value (same behavior as Chrome).

Does this also happen when you use the default classic theme in helium://settings/appearance?

[Acumane]

No, the classic theme follows my color scheme preference