Re: Bus failure using focus events

[Ian Schorr <spamcontrol2 comcast net>]

Hi Peter,

I'm not sure I understand.  When I refer to using activate and 
focus-out-event, I'm talking about in seperate builds of the product - 
I change the signal type to "activate" and recompile, for example.  
"activate" should never come into play when I'm using a 
"focus-out-event".

However, I noticed the different params and I'm not sure that I'm 
handling this properly (I don't believe I understand signals terribly 
well, to be honest with you).  I had assumed that in none of the code 
I've implemented, do I have to worry about the signal params - those 
were handled by GTK.  I just connect to the signal, and pass the 
signal-connect params.  Are you saying that I somehow have to build a 
GdkEventFocus object and pass it to focus-out-event?  I'm not sure that 
I'm actually generating the call with the GtkEntry or gpointer when I 
connect to "activate" now, so I'm not sure at what point this would be 
done.

Thanks,
Ian

On Thursday, October 2, 2003, at 11:46 AM, Peter Krueger wrote:

> Hi Ian,
> when you connect a callback function you have to make sure that the
> functions parameter list is appropriate to the signal you connect it 
> to.
> You can't use the same callback function since they have a different
> signature:
>
> "activate" void user_function(
>   GtkEntry *entry,
>   gpointer user_data);
>
> "focus-out-event" gboolean user_function(
>   GtkWidget *widget,
>   GdkEventFocus *event,
>   gpointer user_data);
>
> When GTK calls the "focus-out-event" it places three arguments for your
> callback function on the stack, but your "activate"-function only 
> removes
> two of them. This means that when your function returns there is still
> some parameter data on the stack where it shouldn't be. This causes 
> your
> application to crash.
>
> Regards...Peter
>
> > I'm trying to generate some code that checks the input a user has
> > provided into a text entry field, and appends a trailing character if
> > needed.  I'd like to do it as soon as the user switches away from the
> > widget, and is presumably done editing.
> >
> > If I use an "activate" signal, things work fine - it does exactly what
> > I expect, with no complaints.
> >
> > However, if I use a "focus-out-event", the program eventually
> > terminates and I get, simply, a "Bus error" message.
> >
> > This happens using GTK+1.2.10, 2.0.6, as well as 2.2.1.
> >
> > Can anyone point me to what I'm doing wrong?
> >
> > Here's some of the code:
> >
> > Here's where I connect the signal and generate the widget:
> >
> > #if GTK_MAJOR_VERSION < 2
> >
> > #define SIGNAL_CONNECT(widget, name, callback, arg) \
> > gtk_signal_connect(GTK_OBJECT(widget), name, 
> > GTK_SIGNAL_FUNC(callback),
> > \
> >                     (gpointer)(arg))
> >
> > #else /* GTK_MAJOR_VERSION >= 2 */
> >
> > #define SIGNAL_CONNECT(widget, name, callback, arg) \
> > g_signal_connect(G_OBJECT(widget), name, G_CALLBACK(callback), \
> >                   (gpointer)(arg))
> >
> >          fileopen_dir_te = create_preference_entry(main_tb, 9,
> > "Directory:", NULL, prefs.gui_fileopen_dir);
> >          OBJECT_SET_DATA(main_vb, GUI_FILEOPEN_DIR_KEY, 
> > fileopen_dir_te);
> >          SIGNAL_CONNECT(fileopen_dir_te, "focus-out-event",
> > fileopen_dir_changed_cb, NULL);
> >
> > Again, if I replace "focus-out-event" with "activate", things work 
> > fine
> > if I just hit enter in the text entry field.
> >
> > static void
> > fileopen_dir_changed_cb(GtkWidget *fileopen_entry _U_, gpointer
> > parent_w)
> > {
> >      char *lastchar;
> >      gint fileopen_dir_te_length;
> >
> >      fileopen_dir_te = (GtkWidget *)OBJECT_GET_DATA(parent_w,
> > GUI_FILEOPEN_DIR_KEY);
> >      fileopen_dir_te_length = strlen(gtk_entry_get_text
> > (GTK_ENTRY(fileopen_entry)));
> >      lastchar = gtk_editable_get_chars(GTK_EDITABLE(fileopen_entry),
> > fileopen_dir_te_length-1, -1);
> >      if (strcmp(lastchar, "/") != 0)
> >          gtk_entry_append_text(GTK_ENTRY(fileopen_entry), "/");
> >      return;
> > }
> >
> > Is there a stupid mistake I made here?
> >
> > Thanks,
> > Ian
> --
> ====================================================================
> Peter Krüger
>
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