GUI.SetMouseEventHandler - OpenTuring Documentation

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.