This example uses the WinUnionRect call to find a rectangle that bounds two source rectangles.

#define INCL_WINRECTANGLES
#include <OS2.H>
HAB hab;
RECTL resultrcl;   /* result. */
RECTL rcla={25,    /* x coordinate of left-hand edge of */
                   /* rectangle. */
            25,    /* y coordinate of bottom edge of    */
                   /* rectangle. */
            125,   /* x coordinate of right-hand edge of */
                   /* rectangle. */
            125};   /* y coordinate of top edge of rectangle. */

RECTL rclb = {15,  /* x coordinate of left-hand edge of */
                   /* rectangle. */
              15,  /* y coordinate of bottom edge of    */
                   /* rectangle. */
              125, /* x coordinate of right-hand edge of */
                   /* rectangle. */
              125};

WinUnionRect(hab,
                &resultrcl,
                &rcla,
                &rclb);