These are functions for getting and setting properties of buttons. Often these are used by a button's invocation function to determine what to do.
Where a button parameter is specified, it means an object referring to a specific button, either an overlay (for overlay buttons), or a buffer-position or marker (for text property buttons). Such an object is passed as the first argument to a button's invocation function when it is invoked.
actionproperty (i.e., invoke it). If use-mouse-action is non-
nil, try to invoke the button's
mouse-actionproperty instead of
action; if the button has no
tif button has button-type type, or one of type's subtypes.
Return the button at position pos in the current buffer, or
nil. If the button at pos is a text property button, the return value is a marker pointing to pos.