Apps' windows are forced to draw CSD despite their preference to SSD

[TheESN]

Some applications such as Alacritty prefer to use Server Side Decorations in Wayland when possible and use Client Side Decorations just for compositors that don't support it (ex. Mutter). However in COSMIC alacritty still draws its CSD despite the fact that cosmic-comp supports SSD. I think the same issue applies to some Qt apps such as OBS Studio

[TheESN]

One of the examples of this issue - PCManFM-Qt draws CSD, despite LXQt apps should use SSD if it's supported in compositor

[BrodieRobertson]

I can confirm the problem occurs in OBS, I've also seen this behavior in GTK3 applications like the GTK3 version of PCManFM. Alacritty does seem to be using the COSMIC decorations at least on my system

[siren15]

I think this applies to a lot of different KDE, or most likely QT, apps. As I see this issue with Konsole, Dolphin, Elisa, NeoChat, KWrite, Kdevelop, Kate, and other apps as well. Started digging into this since they had different theme of the headerbar, with some having also different window buttons. And the only explanation would be them using CSDs(having them as backup for like gnome, etc...) instead of SSDs. When they should be using SSDs.

[michaelBelsanti]

I believe this is also occurring with Ghostty. SSD works as expected on Plasma, but not on Cosmic.

Relevant Ghostty docs: https://ghostty.org/docs/config/reference#window-decoration