Make Qt apps follow dark mode setting

[jaxvanyang]

For Qt you need to set QT_QPA_PLATFORMTHEME=xdgdesktopportal environment variable, and possibly install additional package depending on a distro.

Originally posted by @equeim in #617

I don't know how this works, but it just simply makes Qt apps follow COSMIC dark/light mode setting. So I wonder would it be better if the COSMIC session set this automatically for us?

[equeim]

It works by making Qt use a plugin that integrates with the portals system (for dark mode, native file dialogs, etc). Normally Qt would do this automatically but it doesn't know about Cosmic so it uses generic fallback that doesn't use portals. Ideally Qt needs a patch that fixes that. Though it won't be possible for Qt 5 apps since it's EOL (but QT_QPA_PLATFORMTHEME should work, provided that the plugin is installed).

[ninelore]

Could this be a bug with the Settings interface of xdg-desktop-portal-cosmic? I've noticed that Firefox repeatedly asks about being the default browser (despite already being the default browser) when i forced it to use the portal via about:config

[jaxvanyang]

Could this be a bug with the Settings interface of xdg-desktop-portal-cosmic? I've noticed that Firefox repeatedly asks about being the default browser (despite already being the default browser) when i forced it to use the portal via about:config

I think it is not related to this issue. On my system (CachyOS), firefox depends on gtk3, so I guess it follows GTK theming. And I also use firefox as default browser, but I didn't experience this. Maybe you should create another issue with your system details and steps to reproduce.

[ninelore]

Could this be a bug with the Settings interface of xdg-desktop-portal-cosmic? I've noticed that Firefox repeatedly asks about being the default browser (despite already being the default browser) when i forced it to use the portal via about:config

I think it is not related to this issue. On my system (CachyOS), firefox depends on gtk3, so I guess it follows GTK theming. And I also use firefox as default browser, but I didn't experience this. Maybe you should create another issue with your system details and steps to reproduce.

Twas more of a question for the devs. The platform theme handles both through the portal