Allow apps that use a dark visual style to request a matching title bar
There are bunch of applications that look very poor with the standard title bar provided by GNOME, due to the fact that their window content is dark but the title bar is light. These include the GIMP, Blender, Spotify and Visual Studio Code. There are also other apps that it would be good to have available for GNOME which could suffer from this issue, particularly Electron apps like GitKraken and Figma.
Obligatory screenshot:
From a UX perspective, it would be better if these apps adopted CSD and header bars (or some similar UI pattern). Apps that use GTK, like the GIMP, could also use the standard dark Adwaita theme.
However, I think there will always be dark apps that don't want to do CSD, at least on GNOME. For these cases, it would be nice to allow them to have a title bar that is more in keeping with the look of the app. This could be through an option to use dark window decorations. Alternatively, we could allow a base colour to be set, which would then be used to define the style of the title bar.
What do you think, @jimmac ?