This allows users to open the clock/calendar popup through DBus, which
means we could configure a keybinding for it.

This in turn emits an 'activate' signal that any applet can connect to
and perform whatever action it means to activate in that applet.

This allows users to control certain applet functionalities through
DBus, like registering new keybindings, or integrating them with other
software.

*Note that in the wayland panel the show desktop applet works by using an invocation of the window list backend to send a signal to every window to mimimize or unminimize
*This however causes every added button to be counted twice when the show desktop applet is also used
*Detect the show desktop applet, and only divide the number of window list buttons by 2 when it is present

The monitor origin needs to be taken into account.

*Set a sane default width of 1/3 the total panel with on startup
*This prevents the panel width from coming up zero or one when GTK gets the allocation with no buttons in it

*Always affirmatively show or hide icons and text when adjusting the buttons for width
*Get the box the tasklist->outer box is packed into for width calculations
*Recompute tasklist width both on adding and removing buttons

*Recompute the maximum button width when three fullsize buttons won't fit
*Otherwise short tasklists overflow