How do I attach Instance data to window created with WinCreateStdWindow?

I always use the two call to WinCreateWindow() method, instead of the WinCreateStdWindow() method, because the latter does not allow you to set instance data before your winproc is called for the first time.

Here's a cset/2 program (icc /Ss+ /W3 /Se /B"/pm:pm" foo.c):

 #define INCL_PM
 #include <os2.h>

 typedef struct _mydata {
     HWND hwndFrame;
     HWND hwndClient;
     char whatever[100];
 }MYDATA;

 static MRESULT EXPENTRY WinProc(HWND hwnd, ULONG msg, MPARAM mp1, MPARAM mp2)
 {
     MYDATA *mine;

    mine = (MYDATA *)WinQueryWindowPtr(hwnd, 0);  // will be null for WM_CREATE
     switch(msg){
         case WM_CREATE:
             mine = (MYDATA *)mp1;
             WinSetWindowPtr(hwnd, 0, mine);
             break;
         case WM_ERASEBACKGROUND:
             return (MRESULT)TRUE;
         default:
            return WinDefWindowProc(hwnd, msg, mp1, mp2);
     }
     return 0;
 }

 void main(void)
 {
     HAB hab;
     HMQ hmq;
     QMSG qmsg;
     char *class = "foo";
     FRAMECDATA fcdata;  /* frame creation data */
     MYDATA mydat;

     hab = WinInitialize(0);
     hmq = WinCreateMsgQueue(hab, hmq);

     WinRegisterClass(hab, class, WinProc, 0, sizeof(MYDATA *));

     /* create frame window (WC_FRAME) */
     fcdata.cb = sizeof(FRAMECDATA);
     fcdata.flCreateFlags = FCF_TITLEBAR | FCF_SYSMENU |
                            FCF_SHELLPOSITION | FCF_TASKLIST |
                            FCF_SIZEBORDER | FCF_MINMAX ;

     fcdata.hmodResources = 0;
     fcdata.idResources   = 1;	     /* resource id */
     mydat.hwndFrame = WinCreateWindow(HWND_DESKTOP, WC_FRAME, "Title",
                                       0, 0, 0, 0, 0,
                                       0,  /* no owner */
                                       HWND_TOP,fcdata.idResources,&fcdata,NULL);

     if(!mydat.hwndFrame)
         exit(3);

     /* WinProc() has not been called yet */

     /* Create Client window: */
     mydat.hwndClient = WinCreateWindow(mydat.hwndFrame, class, "text",
                         0, 0, 0, 0, 0,
                         mydat.hwndFrame,    /* frame is owner */
                         HWND_TOP, FID_CLIENT,
                         &mydat, /* passed as mp1 to wm_create */
                         NULL);

     WinShowWindow(mydat.hwndFrame, TRUE);

     while(WinGetMsg(hab, &qmsg, (HWND) NULL, 0, 0))
         WinDispatchMsg(hab, &qmsg);

 }

Credit: Peter Fitzsimmons