GUI.SetKeyEventHandlerPart of GUI module

Syntax   GUI.SetKeyEventHandler (
    keyEventHandler : procedure x (ch : char))

Description   Sets the new default keystroke event handler. The keyEventHandler parameter is the name of a procedure that is called every time GUI.ProcessEvent is called and there is a keystroke which is not handled by any widget. The ch parameter in the keyEventHandler is the keystroke typed by the user.

This procedure is often used to allow for more than one shortcut character for a given button.

Example   The following program draws a star or quits depening on the button. The Draw Star button can be activated by clicking on it or typing 'D', 'd', 'S', 's' or Ctrl+S. The Quit button can be activate by typing 'Q', 'q' or Ctrl+Q. The Draw Star button is also the default button. It is activated whenever the user presses ENTER.

        import GUI
        View.Set ("graphics:220;200")
        procedure DrawStar
            Draw.FillStar (25, 40, 175, 190, Rand.Int (10, 15))
        end DrawStar
        procedure KeyHandler (ch : char)
            if ch = 'q' or ch = '^Q' then
            elsif ch = 'd' or ch = '^d' or ch = 'S' or ch = 's' or ch = '^s' then
            end if
        end KeyHandler
        GUI.SetKeyEventHandler (KeyHandler)
        var button : int := GUI.CreateButtonFull (5, 5, 100, "Draw Star",
            DrawStar, 0, 'D', true)
        var quitButton : int := GUI.CreateButtonFull (115, 5, 100, "Quit", 
            GUI.Quit, 0, 'Q', false)
            exit when GUI.ProcessEvent
        end loop
Status   Exported qualified.

This means that you can only call the function by calling GUI.SetKeyEventHandler, not by calling SetKeyEventHandler.

See also   GUI.ProcessEvent.