This function obtains the recommended size, position and status for the first window of a newly started application (typically the main window).

#define INCL_WINSWITCHLIST /* Or use INCL_WIN, INCL_PM, */
#include <os2.h>

HAB      hab;   /*  Anchor-block handle. */
ULONG    ulID;  /*  Session. */
PSWP     pswp;  /*  Window position and size data. */
ULONG    rc;    /*  Return code. */

rc = WinQueryTaskSizePos(hab, ulID, pswp);