Add CSD to border modes

[RyanDwyer]

This replaces view.using_csd with a new border mode: B_CSD. This also removes sway_xdg_shell{_v6}_view.deco_mode and view->has_client_side_decorations as we can now get these from the border.

You can use border toggle to cycle through the modes including CSD, or use border csd to set it directly. The client must support the xdg-decoration protocol, and the only client I know of that does is the example in wlroots.

If the client switches from SSD to CSD without us expecting it (via the server-decoration protocol), we stash the previous border type into view.saved_border so we can restore it if the client returns to SSD. I haven't found a way to test this though.

Closes #2429.

[ddevault]

I suppose I can throw out my WIP xdg-decoration branch 😄

[emersion]

I tried to use "set" for the server-side and "update" for the client-side. Is it possible to rename this to view_update_csd_from_client?

[emersion]

current_mode isn't the client preference, it's the current mode as chosen by the compositor.

To get the client preference, listen to request_mode.

[RyanDwyer]

Copying my latest commit message into here...

This does the following:

• Removes the xdg-decoration surface_commit listener. I was under the impression the client could ignore the server's preference and set whatever decoration they like using this protocol, but I don't think that's right.
• Adds a listener for the xdg-decoration request_mode signal. The protocol states that the server should respond to this with its preference. We'll always respond with SSD here.
• Makes it so tiled views which use CSD will still have sway decorations rendered. To do this, using_csd had to be added back to the view struct, and the border is changed when floating or unfloating a view.

Also note that when testing with the wlroots toplevel-decoration example, that example does not support server-decoration, so according to the server-decoration protocol we assume the client is using CSD. However, the example client believes it's using SSD as that's sway's default, so there's a mismatch there until the first time you change the border. Fixed by removing server-decoration assumption if view supports xdg-decoration.

[ddevault]

This can be a separate patch, but I wonder if we should make XDG windows tiled on all four sides if they're floating with a server-side border. Then GTK for example will stop using rounded corners.

[emersion]

I wonder if we should make XDG windows tiled on all four sides if they're floating with a server-side border

If we do, we should only do so if server-decoration says the window is using CSD and xdg-decoration isn't supported.

[ddevault]

Thanks!