Wayland Protocols 1.43 Released With Toplevel Tag Protocol

Written by Michael Larabel in Wayland on 8 April 2025 at 08:18 AM EDT. 44 Comments

Wayland Protocols 1.43 is out this morning with one new protocol: xdg_toplevel_tag_v1.

The new addition to Wayland Protocols 1.43 is Toplevel Tag "xdg_toplevel_tag_v1" for allowing Wayland clients to tag top-levels in a script-friendly manner. KDE developer Xaver Hugl worked on this Toplevel Tag protocol that had been under review/discussion since July 2023. Xaver sums up the new protocol in the merge request as:

"The toplevel tag protocol allows clients to set a tag for toplevels, which the compositor can use to identify them even after the application has been restarted. This persistent identification can be used by the compositor to restore properties like position, size, "always on top", and it can also be used for allowing users to create rules that change compositor behavior for specific windows."

There are tentative toplevel tag implementations already in existence for KDE KWin, GNOME's Mutter, and the GTK toolkit. The KWin merge request sums up the new functionality as:

"It allows applications to tag their windows with a name, like "main window", "email composer", "pip video" or similar, which the compositor can use for window rules or restoring state of application windows without xdg session management support.

We also (optionally) get a translated window description, which we could use for accessibility purposes later on."

The Wayland Toplevel Tag protocol is documented via this merge request.

👁 toplevel_tag protocol MR

The Wayland Protocols 1.43 update besides xdg_toplevel_tag_v1 has just some minor fixes and adding edge constraints to the XDG-Shell protocol. That's it for today's release.