virtual void            ConvertToDeviceCoordinates(nscoord	&aX,nscoord	&aY) {}
nsWindow::ConvertToDeviceCoordinates(nscoord &aX, nscoord &aY) { PRInt32	offX, offY; CalcOffset(offX,offY);  aX += offX; aY += offY; }
   	virtual void            ConvertToDeviceCoordinates(nscoord	&aX,nscoord	&aY) {}