Action generated when the element is activated. Affects each element differently.
int function(Ihandle *ih); [in C] ih:action() -> (ret: number) [in Lua]
ih: identifier of the element that activated the event.
In some elements, this callback may receive more parameters, apart from ih. Please refer to each element's documentation.
IupButton, IupItem, IupList, IupText, IupCanvas, IupMultiline, IupToggle