XPolygonRegion, XClipBox - generate regions
Region XPolygonRegion(XPoint points[], int n, int
    fill_rule);
int XClipBox(Region r, XRectangle
  *rect_return);
  - fill_rule
- Specifies the fill-rule you want to set for the specified GC. You can pass
      EvenOddRule or WindingRule.
- n
- Specifies the number of points in the polygon.
- points
- Specifies an array of points.
- r
- Specifies the region.
- rect_return
- Returns the smallest enclosing rectangle.
The XPolygonRegion function returns a region for the polygon defined by
  the points array. For an explanation of fill_rule, see XCreateGC.The XClipBox function returns the smallest rectangle
    enclosing the specified region.
XCreateGC(3), XDrawPoint(3), XDrawRectangle(3)
Xlib - C Language X Interface