public void onModuleLoad() 

{

    RootPanel rp  = RootPanel.get() ;

    canvas   = new myCanvas(1024,650) ; // set canvas size

    

    rp.add(canvas) ; // add canvas to root panel

}

class myCanvas extends GWTCanvas implements MouseDownHandler, MouseMoveHandler , MouseUpHandler

{

public myCanvas(int i,int j)

{

super(i,j) ;

this.addMouseDownHandler(this) ;    // add listener

this.addMouseMoveHandler(this) ;    // add listener

this.addMouseUpHandler(this) ;        // add listener

}

public void onMouseDown(MouseDownEvent e) 

{

// code here

}

public void onMouseMove(MouseMoveEvent e) 

{

// code here

}

public void onMouseUp(MouseUpEvent e) 

{

// code here

}

public HandlerRegistration addMouseDownHandler(MouseDownHandler handler) 

{

             return addDomHandler(handler, MouseDownEvent.getType());

        }

public HandlerRegistration addMouseMoveHandler(MouseMoveHandler handler) 

{

             return addDomHandler(handler, MouseMoveEvent.getType());

        }

public HandlerRegistration addMouseUpHandler(MouseUpHandler handler) 

{

             return addDomHandler(handler, MouseUpEvent.getType());

        }

}