int down_coord = getDownCoord();
gc.fillPolygon(new int[] { up_coord,y,down_coord,y,down_coord,y + bar_height, up_coord, y + bar_height});
// draw pointers
gc.setBackground(pointerColor);
gc.fillPolygon(new int[] { up_coord, y, up_coord + pointer_width, y - pointer_height, up_coord - pointer_width, y - pointer_height});
int y2 = y + bar_height;
gc.fillPolygon(new int[] { down_coord, y2, down_coord + pointer_width, y2 + pointer_height, down_coord - pointer_width, y2 + pointer_height});
gc.dispose();
}