Yet another swaybar ipc implementation - #1244

This feature makes waybar a client for the Sway bar IPC protocol and allows controlling some aspects of the bar behavior with swaymsg

Documentation: i3 bar display modes, sway-bar(5)

Quickstart

Prerequisites:

• Sway
• Single bar configuration block (i.e. $XDG_CONFIG_HOME/config/waybar is a JSON object)
• The bar is started from the sway config with swaybar_command waybar

Configuration

1. Add "ipc": true to the waybar configuration
2. Set the desired mode, hidden_state and modifier in the same bar configuration block as swaybar_command
   • Sway will assign the default identifier bar-0 to the only bar instance and run waybar as /usr/bin/waybar -b bar-0
   • Waybar will read one bar configuration; create a bar; connect to the sway IPC with the bar id bar-0 provided via commandline argument and get the initial configuration
   • Only after that waybar will create a window with the mode specified in the sway config.
3. Control the bar mode/visibility with swaymsg bar mode <mode> bar-0, swaymsg bar hidden_state <show|hide> bar-0 (note the trailing bar_id syntax)

Multiple bars

Your $XDG_CONFIG_HOME/config/waybar is a JSON array with multiple bars defined.

• If you don't want a particular bar instance to be controlled via IPC, simply don't add the ipc option to the corresponding config block. It will default to disabled.
• If you want the bar instance to be controlled with the id from sway config (the one specified in the bar config block with swaybar_command waybar) - add only "ipc": true. Sway will pass the bar_id and the bar instance will use that value.
• If you want the bar instance to be controlled with a separate bar id (i.e. you have two bar configuration blocks in the sway config), set the id in the waybar config for the corresponding bar instance ("id": "bar-1") and then use this identifier for the swaymsg command invocation: swaymsg bar mode hide bar-1

Example configuration:

bar  {
        # will asssign id 'bar-0' by default
	swaybar_command /path/to/waybar
	mode dock
	position top
}

# the id can be set with `bar <id> { ... }` or with the `bar { id <id>; ... }`
# if you don't specify the id explicitly, sway will assign `bar-1`
bar bar-1 {
        # placeholder command, so that sway could create the configuration but won't run an actual second bar instance
	swaybar_command /bin/true
	mode hide
	position bottom
}

[
{ // bar id is passed via `-b bar-0` commandline argument from sway
  // will react only to the events for "bar-0" or for any bar
	"ipc": true,
	"position": "top",
	...
},
{ // bar id is explicitly set to "bar-1"
  // will react only to the events for "bar-1" or for any bar
	"id": "bar-1",
	"ipc": true,
	"position": "bottom",
	...
}
]

The bar_id parameter is required for IPC subscription.

Test commands (note the trailing bar_id syntax. bar <bar-id> mode ... is broken in sway and will modify config for all the defined bars - swaywm/sway#6680):

swaymsg bar mode dock bar-1
swaymsg bar mode hide bar-1
swaymsg bar hidden_state show bar-1
swaymsg bar hidden_state hide bar-1
swaymsg bar mode overlay bar-0
...

Non-blocking issues:

• Defaults for bar_id - do we want to assume bar-0 or to take the first entry from get_bar_config result if it's not set explicitly?
  bar-0 is assumed if no other value is passed. The swaybar IPC client will try to get the initial configuration for the bar_id and disable itself if the sway config does not have the bar with that id.

• setVisible should be controlled either via signals or via IPC. Allowing both at the same time makes things messy and inconsistent.
  setVisible was changed to switch between invisible and default modes. That addressed most of the problems, the only remaining is to remember the last visible mode and use it instead of the default.

• Copy/move optimizations for SafeSignal

• D-Bus method for changing mode or visibility when sway IPC is not available (but definitely not in this PR)

• Support for custom modes/mode configuration overrides;

  example:

  "modes": {
    "dock": {
      "layer": "top"
    },
    // show overlay bar over fullscreen applications
    "overlay": {
      "layer": "overlay"
    },
    // hide bar under the current window instead of making it invisible
    "invisible": {
      "passthrough": false,
      "visible": true
    } 
  }