1934140 - When Mica is enabled, sub-window title bars also use the Mica Alt effect, even though they are regular windows with no tabs whatsoever

Status: RESOLVED DUPLICATE of bug 1944998

(Core :: Widget: Win32, defect, P3)

Description

[kanapa1]

Attachment: The library window with the Mica Alt effect that has stronger tinting

Steps to reproduce:

1. Make sure that:
   • you are using Firefox version 133 stable
   • support for the Mica effect from Windows 11 is enabled in the advanced settings via the widget.windows.mica pref
   • you are using the default theme, i.e. System theme — auto, or any other light theme because dark themes force title bars to be dark, which overrides the Mica effect (this may be a separate bug?)
     If these three conditions are met, proceed to the next step.
2. Start Firefox.
3. Open any sub-window or modal window, such as the library (Ctrl + Shift + H), the browser console (Ctrl + Shift + J), the Page Info window (Ctrl + I), the About Firefox window (Application hamburger menu > Help > About Firefox), or even the Removing Cookies and Site Data modal window (Padlock in the address bar > Clear cookies and site data...).
4. Look at the title bar of the newly opened sub-window or modal window and see what is described in the "Actual results" section.

Actual results:

The title bars in all sub-windows and modal windows (and there are still quite a few of them, as not all of them have been modernized yet) incorrectly use the Mica Alt effect, even though they are regular windows with no tabs whatsoever, so there is no reason to use it there because "a deeper visual hierarchy than Mica, especially when creating an app with a tabbed title bar", as Microsoft recommends (source), does not apply there.

Expected results:

The tab bar background should continue to use the Mica Alt effect. Sub-windows and modal windows, however, should just hint the window manager to style them like regular native windows with server-side decorations (which effectively means, in the case of the current Windows 11 version, to use the normal Mica effect).

Comment 1

[Emilio Cobos Álvarez [:emilio]]

Yeah, we currently hard-code it here. We should do something more subtle (maybe hooking it up a bit more tightly with the front-end).

Comment 2

[Emilio Cobos Álvarez [:emilio]]

Bug 1944998 fixes this.