public void pan( double deltax, double deltay) {
    zoom.push();

    pix_x0 -= deltax;
    pix_y0 -= deltay;
    fireMapAreaEvent();
  }
public void pan( double deltax, double deltay) {
    zoom.push();

    pix_x0 -= deltax;
    pix_y0 -= deltay;
    fireMapAreaEvent();
  }
public void pan ( double deltax , double deltay ) { zoom . push ( ) ; pix_x0 -= deltax ; pix_y0 -= deltay ; fireMapAreaEvent ( ) ; }
call this to change the center of the screen's world coordinates.
deltax, deltay in display coordinates
call this to change the center of the screen s world coordinates . deltax deltay in display coordinates