Add support for command line arguments to set default values for the
various options of rivertile, bringing us back to rough feature parity
with before the commit removing the river-options protocol.
This protocol involves far too much accidental complexity. The original
motivating use-case was to provide a convenient way to send arbitrary
data to layout clients at runtime in order to avoid layout clients
needing to implement their own IPC and do this over a side-channel.
Instead of implementing a quite complex but still rigid options protocol
and storing this state in the compositor, instead we will simply add
events to the layout protocol to support this use case.
Consider the status quo event sequence:
1. send get_option_handle request (riverctl)
2. roundtrip waiting for first event (riverctl)
3. send set_foo_value request (riverctl)
4. receive set_foo_value request (river)
5. send foo_value event to all current handles (river)
6. receive foo_value event (rivertile)
7. send parameters_changed request (rivertile)
8. receive parameters_changed request (river)
9. send layout_demand (river)
And compare with the event sequence after the proposed change:
1. send set_foo_value request (riverctl)
2. receive set_foo_value request (river)
3. send set_foo_value event (river)
4. send layout_demand (river)
This requires *much* less back and forth between the server and clients
and is clearly much simpler.
Options are now all global but may be overridden per-output. If an
output local value is requested but none has been set, the global value
is provided instead. This makes for much better ergonomics when
configuring layout related options in particular.
Replace the current layout mechanism based on passing args to a child
process and parsing it's stdout with a new wayland protocol. This much
more robust and allows for more featureful layout generators.
Co-authored-by: Isaac Freund <ifreund@ifreund.xyz>
main is a better term to use here for several reasons:
1. It is more accurate: "master" implies that the designated views have
some kind of control over the other views, which is not the case. "main"
better expresses that the difference between the "main" view and others
is one of importance/focus.
2. It is a shorter word. 2 whole characters saved!
3. It reduces the chance of future development time being lost to
good-intentioned people complaining about usage of the word master as
has recently happened with regards to the default git branch name.
