Action generated when the mouse wheel is rotated. If this callback is not defined the wheel will automatically scroll the canvas in the vertical direction by some lines, the SCROLL_CB callback if defined will be called with the IUP_SBDRAGV operation.
int function(Ihandle *ih, float delta, int x, int y, char *status); [in C] ih:wheel_cb(delta, x, y: number, status: string) -> (ret: number) [in Lua]
identifier of the element that activated the event.
delta: the amount the wheel was rotated in notches.
x, y: position in the canvas where the event has occurred, in pixels.
status: status of mouse buttons and certain keyboard keys at the moment the event was generated. The same macros used for BUTTON_CB can be used for this status.
In Motif and GTK delta is always 1 or -1. In Windows is some situations delta can reach the value of two. In the future with more precise wheels this increment can be changed.