*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

*Do not hide text and retain icons, that's not what we do in x11
*Hide the icons first, only hide labels when ellipsized text can no longer fit
*ensure last buttons don't over-expand as windows are closed
*divide available panel space by number of buttons to set size of empty buttons on crowded panel
*This more evenly fills the window list when a crowded window list forces empty buttons
*and allows far more buttons to show before the window list pushed other applets off the panel

A previous overzealous cleanup left some hanging screen variables and
one instance of an uninitialized screen being used.