Re: XForms: Spurious callback call

j.w.c.a. lokin (lokin@signaal.nl)
Mon, 18 Oct 1999 09:14:52 +0200

# To subscribers of the xforms list from "j.w.c.a. lokin" <lokin@signaal.nl> :

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Steve Lamont wrote:
>
> # To subscribers of the xforms list from spl@szechuan.ucsd.edu (Steve Lamont) :
>
> > Should an fl_hide_object() on an input object actually call the object callback
> > function? I noted that it does, since it makes my program crash.
>
> No, it shouldn't. I did a simple test and the callback was not called.
>
> Can you provide a simple example which exhibits the behavior?
>

See the attached file. Note that the call is done as part of a hide on
a group.
Waht TC said seems to make sense, but I can't see how I should check
from within
my callback. Or am I missing something somewhere?

-- 
-+- Jan Willem Lokin -+-
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#include <stdlib.h>
#include "forms.h"


struct TrkChoice 
{
  FL_OBJECT *group, *input, *message, *id, *data;
  void (*callback) (void);
};


static void chc_prev_func (FL_OBJECT *obj, long n)
{
  fprintf (stderr, "%s (%p, %ld)\n", __FUNCTION__, obj, n);
}




static void chc_input_func (FL_OBJECT *obj, long n)
{
  fprintf (stderr, "%s (%p, %ld)\n", __FUNCTION__, obj, n);
}




static void chc_next_func (FL_OBJECT *obj, long n)
{
  fprintf (stderr, "%s (%p, %ld)\n", __FUNCTION__, obj, n);
}




#define CHC_SET_CALLBACK(cb)					\
  fl_set_object_callback (obj, cb, 0);				\
  obj->u_vdata = this


struct TrkChoice *add_trk_choice (int x, int y, int w, int h)
{
  struct TrkChoice *this = malloc (sizeof (struct TrkChoice));
  FL_OBJECT *obj;


  this->group = fl_bgn_group ();


  obj = fl_add_button (FL_NORMAL_BUTTON, x+h, y, h, h, "@<");
  CHC_SET_CALLBACK (chc_prev_func);


  this->input = obj = fl_add_input (FL_INT_INPUT, x+h+h, y, w-h, h, "");
  fl_set_input (obj, "");
  CHC_SET_CALLBACK (chc_input_func);


  obj = fl_add_button (FL_NORMAL_BUTTON, x+h+w, y, h, h, "@>");
  CHC_SET_CALLBACK (chc_next_func);


  fl_end_group ();


  this->callback = 0;


  return this;
}




int main (int argc, char *argv[])
{
  FL_FORM *form;
  struct TrkChoice *this;


  fl_initialize (&argc, argv, 0, 0, 0);


  form = fl_bgn_form (FL_FLAT_BOX, 200, 50);
  this = add_trk_choice (0, 0, 60, 20);
  fl_end_form ();
  fl_show_form (form, FL_PLACE_FREE, FL_FULLBORDER, argv[0]);
  fl_hide_object (this->group); /* this is the offending call */
  fl_do_forms ();


  fprintf (stderr, " *** Unexpected fallthru ***\n");
  return 0;
}


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