gui_setmouseeventhandler

#GUI.SetMouseEventHandler

##Syntax GUI.SetMouseEventHandler ( mouseEventHandler : procedure x (mx, my : int))

##Description Sets the new default mouse event handler. The mouseEventHandler parameter is the name of a procedure that is called every time GUI.ProcessEvent is called and there is a mouse button down which is not handled by any widget. The mx and my parameters in the mouseEventHandler are the location of mouse when the button was pressed.

This procedure is used by programs to allow for mouse input in a program that uses widgets.

##Example This is a program that allows the user to place stars on the screen. The menu bar allows the user to quit the program at any time. The user can also toggle the appearance of the menu bar by pressing any key.

    import GUI
    
    var starX, starY, starColor : array 1 .. 100 of int
    var numStars : int := 0
    var menuVisible : boolean := true
    
    procedure DrawStar (i : int)
        if menuVisible then
            View.ClipSet (0, 0, maxx, 
                maxy  GUI.GetMenuBarHeight)
        end if
        Draw.FillStar (starX (i)  20, starY (i)  20, starX (i) + 20,
            starY (i) + 20, starColor (i))    View.ClipOff
    end DrawStar
    
    procedure Redraw
        for i : 1 .. numStars
            DrawStar (i)
        end for
        Text.Locate (maxrow, 1)
        put "Press any key to toggle menu bar" ..
    end Redraw
    
    procedure KeyHandler (ch : char)
        if menuVisible then
            GUI.HideMenuBar    else
            GUI.ShowMenuBar
        end if
        menuVisible := not menuVisible
        Redraw
    end KeyHandler
    
    procedure MouseHandler (x, y : int)
        if numStars = 100 then
            Text.Locate (maxrow, 1)
            put "Maximum number of stars exceeded!" ..
            return
        end if
        numStars += 1
        starX (numStars) := x
        starY (numStars) := y
        starColor (numStars) := Rand.Int (9, 15)
        DrawStar (numStars)
    end MouseHandler
    
    var menu : int := GUI.CreateMenu ("File")
    var menuItem : int := GUI.CreateMenuItemFull ("Quit", 
        GUI.Quit, '^Q', false)
    GUI.SetKeyEventHandler (KeyHandler)
    GUI.SetMouseEventHandler (MouseHandler)
    Redraw
    loop
        exit when GUI.ProcessEvent
    end loop

##Status Exported qualified.

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

##See also gui_processevent.html.