ungrab_button(+ButtonUngrab, +ModifiersMask, +UngrabWindow)
Releases the passive button/key combination grab on the specified window, if it was grabbed by the client. It has no effect on an active grab.
ButtonUngrab is the pointer button to be released, possible values are:
ModifiersMask is one of:
modifiers_mask/2is useful to translate between modifier specifications and bitmasks.
UngrabWindow is the ProXL window where the grab is in effect.