river: Allow applying CSD based on window titles

[ThreeFx]

This extends the csd-filter-add command to allow matching on window
titles as well, using a csd-filter-add kind pattern syntax. The
following kinds are supported:

• title, which matches window titles
• app-id, which matches app ids

Only exact matches are considered.

As an example following configuration applies client-side decorations to
all windows with the title 'asdf with spaces'.

riverctl csd-filter-add title 'asdf with spaces'

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This commit makes the *-filter-add consistent over floats and csds.

[ThreeFx]

I'm not clear on what semantics we want to have for csd-filter-add. When should a view have client-side decorations? My current understanding of the current implementation is:

• When the app-id filter matches the view's toplevel

What semantics do we want when also including the title? Currently, I think I've implemented it the following way:

• When the app-id or title matches the view itself

I don't have enough experience with Wayland to judge whether this is ok or not.

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Separate point:

Adding/removing filters at runtime works for both app-id filters as well as title filters, but as is the case with floating, this currently does not handle title updates. Since csds are applied for existing and new windows, should we handle title updates in this case?

[Leon-Plickat]

Only use CSD if the filter matches is the right thing here. This filter exists mostly for cosmetics.

I don't think we should care about updating titles. Eventually all this will be done by an external program, which can deal with that sort of thing.

[ifreund]

For any given view, the view's app-id and title are exactly the app-id and title of the view's backing xdg-toplevel. River's View struct exists purely to abstract over xwayland surfaces and normal xdg-toplevels. So, the way you've implemented that part looks good to me.

With regards to title updates, I'm not sure if it makes sense to handle them or not. Therefore let's go with the simpler option of not handling them for now and see if anyone comes up with a motivating use-case for doing so.

[ThreeFx]

Alright, then this is ready for review. I've added a short note to riverctl(1) stating that we do not account for title updates.

I haven't tested this though, because I haven't got the slightest clue which apps use csd and which don't. Let me know which ones are good test candidates.

[ifreund]

I haven't tested this though, because I haven't got the slightest clue which apps use csd and which don't. Let me know which ones are good test candidates.

All apps theoretically support CSD thanks to GNOME's influence on early wayland developement.

I usually just test this stuff with foot, you should see a title bar appear if you run riverctl csd-filter-add app-id foot.

[ThreeFx]

Ah indeed, thanks! I've tested it using my terminal (Alacritty) with both app-id and title - works like a charm.

[ifreund]

LGTM thanks!