> precise window dimensions
The following example (will work at least in sh, bash and zsh) will print window geometry with and without frame for all windows with "KWrite" somewhere in title.
windows="$(wmiface findNormalWindows "KWrite" "" "" "" "" "")"
for window in $(echo $windows); do
wmiface framePosition $window
wmiface frameSize $window
wmiface windowPosition $window
wmiface windowSize $window
> precise available screen space (excluding panels like gnome-panel)
xrandr | head -n1 | cut -d, -f2 | cut -d" " -f3-5
Output in my case:
4400 x 2560
Not sure how to exclude panels - if you have more than one monitor, they can be even in middle of virtual screen, so screen geometry without panels can be more complicated than "available screen space".
> the ability to set a window to be a certain size, including decorations
wmiface setFrameGeometry $window $x $y $width $height
Read wmiface README for even more possible commands.