draw_ring (GM) (Improved)

/*
**  usage:
**      draw_ring(x, y, radius, thickness, quality)
**
**  given:
**      x,y       center point of the ring
**      radius    distance from the center to the outermost point of the ring
**      thickness thickness of the ring outline
**      quality   granularity of the drawing, ie number of vertices. default 32. try low numbers like 3-8 to make outlined n-gons.
**
**
**  GMLscripts.com
*/
{
    var xx=argument0,yy=argument1,rad=argument2,thick=argument3,qual=32;
    if argument4>0{qual = argument4;}

    draw_primitive_begin(pr_trianglestrip);
    var i;
    for(i=0;i<=qual;i+=1)
    {
        draw_vertex(xx+lengthdir_x(rad,i*360/qual),yy+lengthdir_y(rad,i*360/qual));
        draw_vertex(xx+lengthdir_x(rad-thick,(i)*360/qual),yy+lengthdir_y(rad-thick,(i)*360/qual));
    }
    draw_primitive_end();
}