GTK4 and theming migration guide

[postsolar]

Happy to see GTK4 port is now complete 🎉
Is there a brief migration guide for GTK4 and #1202?

My setup is:

• GTK3: phocus theme
• GTK4 configured like this and aims to provide a simple emulation of GTK3 phocus
• Ironbar styles are here - past approach: don't interfere with GTK3 theme, let it be a sane baseline and adjust atomically where needed

When I updated today to latest master all styles broke. I downgraded to latest release (0.17.1) and it got fine again.

Specifically, buttons' background (which I don't set in my user CSS) was white, which makes me suspect it was using Adwaita as the baseline style, and not my GTK4 config. I think there were also some issues with tray menus, but I didn't have time to properly confirm, will compile and do so a bit later.

I guess my goal is: make it use GTK4 config (as linked above) as the baseline (GTK4 apps do - nemo, overskride, chrome, etc), then adjust my user styles on top of that. So a short comment on how it all works and what to expect could help me a lot.

[JakeStanger]

Hey, I've covered everything I'm aware of for migrating here, although it's from an Ironbar perspective rather than system configuration:
https://github.com/JakeStanger/ironbar/wiki/gtk4

The new themes system is very simple at the moment - it's just a couple of baseline configs and CSS files (examples/minimal and examples/desktop) which are baked in. You can use these as starting points or for guidance. They're also intended to provide sensible defaults where users don't want to write their own configs.

In regards to theme-specific issues, I'm not sure how much help I can provide. Ironbar will load your system gtk theme and icon theme without needing to configure anything.

The example CSS sheets try to provide sensible values that work regardless of theme, but there are likely a lot of holes in that. I would check you've set the theme using dconf as well as the ini file.

NixOS could have something to do with it, but I can't see that it would.

[postsolar]

Oh, I see now. Yeah it used to be the other way around. Thanks for clarifying!

---

As for themes, I do begin suspecting maybe there's something to how Ironbar loads them:

• Command overskride lauches Overskride, a GTK4 app with my config from ~/.config/gtk-4.0/gtk.css applied.
• Sanity checks: GTK_THEME=Adwaita:dark overskride and GTK_THEME=Adwaita:light overskride produce different results than just overskride. Same with other GTK4 apps.
• But ironbar and GTK_THEME=Adwaita:light ironbar are equivalent.

[JakeStanger]

This is icon theme related, but a very recent discovery:
#1213 (comment)

No idea if this could be related?

[postsolar]

I know I could just do

* {
  all: unset;
}

In my user Ironbar CSS but it would wipe out too much low-level stuff. Same issue with trying to fix it surgically atop Adwaita, too much low-level stuff to handle.

[JakeStanger]

But ironbar and GTK_THEME=Adwaita:light ironbar are equivalent.

This is strange. For me, ironbar loads my Arc-Darker theme, which is the GTK3/4 system default. I've got the dconf key set, and the theme set in the gtk4.ini file, but I've never had to do anything else

[postsolar]

No idea if this could be related?

Don't know, I'm not that deep into GTK stuff, also never touched anything icons (neither in Ironbar nor on system level). I tried to build with this commit and it didn't change anything.

This is strange. For me, ironbar loads my Arc-Darker theme, which is the GTK3/4 system default. I've got the dconf key set, and the theme set in the gtk4.ini file, but I've never had to do anything else

Yep, GTK4 is unfortunately quite complicated with regards to theming 😆 Each setup is apparently unique. I guess I'll just use GTK3 release for a few weeks for now, and hopefully I could find something about this by then.

[postsolar]

@JakeStanger could you try reproducing this with:

1. Install any of overskride, gradia, smile, pwvucontrol (GTK4 apps I have installed).
2. Unset GTK4 theme.
3. Put gtk.css in ~/.config/gtk-4.0/gtk.css.
4. Run the installed app and confirm the theme is black.
5. Empty ~/.config/gtk-4.0/gtk.css – don't delete it, just make it empty.
6. Run the installed app and confirm the theme is white.

I think it suggests Ironbar skips something that all these apps do, that is, it only works with an explicitly set GTK4 theme but not with GTK4 user CSS.

[postsolar]

I think I now understand what my issue is. I basically don't have any GTK 4️⃣ theme installed in any meaningful way, just some libadwaita tweaks. But this seemed to work and I thought I'm meant to be covered because all GTK4 apps I used so far were libadwaita-based. Ironbar is not one, so my settings have no effect. Logs and some tweaking with loading config CSS seem to confirm this.

Basically user error :)

[JakeStanger]

Wondering if it's worth documenting that somewhere/somehow, as the difference between GTK4 and libadwaita is (as demonstrated) not always very well known.

[postsolar]

Yes, I think 1-2 sentences in wiki/Styling Guide.md would potentially save everyone quite a few hours. I wouldn't volunteer myself though as I'm not involved enough to formulate the gotchas well enough 😄