Date: 24 Apr 88 14:24:35 GMT
Comment:  Extracted from Info-Atari16 (INFO-A16) digest number 88-215
From: braner@tcgould.tn.cornell.edu  (braner)
Subject: converting a TOS prg into a DA (C source by Moshe Braner)
To: info-atari16@score.stanford.edu

/*
Thought this might be useful for some people.  This seems to be about
the minimum code needed to convert a TOS program to a desk accessory.
Note the "manual" saving and restoring of the menu bar bitmap.
Note that a DA should not use dynamic memory allocation.
(The DA version of GNOME uses a large static array to do its own
internal malloc()ing from.)
Also beware: the "current directory", as the DA sees it, can change
between openings since the current application can change it and GEMDOS
only keeps one "current directory".  Surprisingly, although the desktop
normally makes the top window the current directory, that is not always
the case!

    - Moshe Braner
*/

/*
   This code manually extracted from a program
   that was actually tested with Laser C.
*/

#include <osbind.h>
#include <obdefs.h>
#include <gemdefs.h>
extern int gl_apid;
int    menu_id, event, ret;
int    xdesk, ydesk, hdesk, wdesk;
int    msgbuff[8];
char    menusave[1520];
main()
{
    int    i;
    char    *cp;
    /* your TOS application's initializations here */
    Cconws ("\033f");    /* disable vt52 cursor    */
    appl_init();
    menu_id = menu_register (gl_apid,"  your DA's name");
    wind_get (0, WF_WORKXYWH, &xdesk, &ydesk, &wdesk, &hdesk);
daloop:
    event = evnt_multi (MU_MESAG,
            0,0,0,0,0,0,0,0,0,0,0,0,0,
            msgbuff,
            0,0, &ret,&ret,&ret,&ret,&ret,&ret);
    /* could have simply used evnt_mesag instead:
        evnt_mesag (msgbuf);        */
    if ((event & MU_MESAG) == 0
        || msgbuff[0] != AC_OPEN
        || msgbuff[4] != menu_id )
            goto daloop;
    graf_mouse(M_OFF,0x0L);
    cp = (char *) Physbase();
    for (i=0; i<1520; i++)
        menusave[i] = *cp++;
    wind_update(TRUE);
    form_dial (FMD_START,
            xdesk, ydesk, wdesk, hdesk,
            xdesk, ydesk, wdesk, hdesk);
    /* enable vt52 cursor if needed */
    /* your TOS application does its thing here */
    /* disable vt52 cursor if on */
    form_dial (FMD_FINISH,
            xdesk, ydesk, wdesk, hdesk,
            xdesk, ydesk, wdesk, hdesk);
    wind_update (FALSE);
    cp = (char *) Physbase();
    for (i=0; i<1520; i++)
        *cp++ = menusave[i];
    graf_mouse(M_ON,0x0L);
    goto daloop;