Topic       : TOS - The Operating System
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Subject     : Programmieren/Atari
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View Ref-File13.14.2.1  A simple xFSL call                                      TOS

In view of the multitude of parameters and setting options, the 
following note seems appropriate:

                             Don't panic!

An xFSL call is simpler than it appears at first. In particular one 
can adopt here the strategy of 'step-by-step refinement', since one 
can set (almost) all parameters to zero at first.

A possible simple xFSL call can look like this, for instance:

     #include <stdio.h>
     #include <aes.h>
     #include <vdi.h>
     #include <xfsl.h>
 
     void call_xfsl (void)
     {
       int xhandle, xret;
       xFSL_PAR xpar;
       PFONTINFO pfont;
       xFSL *xfsl;
 
       memset (&xpar, 0, sizeof (xFSL_PAR));
       memset (&pfont, 0, sizeof (PFONTINFO));
 
       xpar.par_size = sizeof (xFSL_PAR);
       xpar.pfi_size = sizeof (PFONTINFO);
       xpar.font = &pfont;
       xpar.font->fontcol = BLACK;
 
       if (get_cookie ('xFSL', &xfsl))
       {
         xhandle = xfsl->xfsl_init (0, &xpar);
         if (xhandle >= 0)
         {
          do
            xret = xfsl->xfsl_event (xhandle, 0L);
          while (xret > xFS_OK);
          xfsl->xfsl_exit (xhandle);
          if (xret == xFS_STOP)
            printf ("Cancel\n");
          else if (xret == xFS_OK)
            printf ("Font with ID %d selected\n", xpar.font->fontid);
          else if (xret < 0)
            printf ("Error %d\n", xret);
        }
        else
          printf ("Error %d\n", xhandle);
       }
       else
         printf ("Cookie not found!\n");
     }

With the two memset calls all elements of the structures xFSL_PAR and 
PFONTINFO are set to zero. Subsequently some absolutely necessary 
values are entered:

   . The size of the two structures xFSL_PAR and PFONTINFO

   . The address of the PFONTINFO structure is entered in the xFSL_PAR 
     structure

   . The font colour is set to black (one could also omit this, but 
     normally one wants to write in black type on a white background)

MNo further preparation is required, and now the actual call follows. 
First the xFSL cookie is searched for and on success the font-selector 
will be initialized by passing the xFSL_PAR structure. If this call 
was successful (xhandle is greater or equal to zero), then the font- 
selector is already on the screen. In the main loop one now waits 
until the font-selector is terminated either with xFS_STOP or xFS_OK 
by the user, or until an error occurs (other positive return values 
are simply ignored here). With the call of xfsl_exit the font-selector 
is removed from the screen once more and subsequently the return value 
is evaluated.

That wasn't too complicated, was it? From here on you can now continue 
experimenting with various parameters and flags.