GTK+ Forums

k_rock923 · Joined: 25 Apr 2008 Posts: 4

I think I have some fundamental misunderstanding with how callbacks work. The following code crashes whenever the callback is called, mostly because I'm not exactly sure how to do what I'm trying to do.

I want to pass the GtkEntry text object to the callback function, but as I said, the application crashes when it gets to this point. If someone could give me an idea of what I'm doing wrong, I'd very much appreciate it.

I understand that this may or may not be how you'd go about this in reality, but I'm just experimenting. What I'm ultimately trying to do is simply read in the contents of the text field on either the button press or the enter key being pressed.

Code: (C)

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int
main( int argc, char **argv )
{
gtk_init( &argc, &argv );

get_user_name();

gtk_main();

return 0;
}

char *
get_user_name()
{
GtkWidget *dialog;
GtkWidget *text;

dialog = gtk_dialog_new_with_buttons( "Name Entry",
NULL,
GTK_DIALOG_MODAL,
GTK_STOCK_OK,
GTK_RESPONSE_ACCEPT,
NULL );
text = gtk_entry_new( );

gtk_container_add( GTK_CONTAINER( GTK_DIALOG( dialog )->vbox ), text );
g_signal_connect( G_OBJECT(dialog),
"response",
G_CALLBACK(text_callback),
text );

gtk_widget_show_all( dialog );

return NULL;
}

void
text_callback( GtkWidget* w, gpointer data )
{
printf( "%s\n", gtk_entry_get_text( x ));
}

Thanks,
Matt

cofcof · Familiar Face Joined: 02 Apr 2008 Posts: 13

Hi Matt

From the GTK API doc:

once you created your gtk_dialog with:

Code: (C)
1 2 3 4 5 6 7 8 9 10 11	dialog = gtk_dialog_new_with_buttons( "Name Entry", NULL, GTK_DIALOG_MODAL, GTK_STOCK_OK, GTK_RESPONSE_ACCEPT, NULL ); text = gtk_entry_new( ); gtk_container_add( GTK_CONTAINER( GTK_DIALOG( dialog )->vbox ), text );

do:

Code: (C)
1 2 3 4 5 6 7 8 9 10 11 12 13	gint result = gtk_dialog_run (GTK_DIALOG (dialog)); switch (result) { case GTK_RESPONSE_ACCEPT: do_application_specific_something (text); break; default: do_nothing_since_dialog_was_cancelled (); break; } gtk_widget_destroy (dialog);

You can define the do_application_specific_something like:

Code: (C)
1 2 3 4 5	do_application_specific_something (GtkEntry * text){ printf( "%s\n", gtk_entry_get_text( text )); }

I believe the advantage of the gtk_dialog is that you don't have to bother with the callback.

clinisbut · Familiar Face Joined: 10 Apr 2008 Posts: 19

k_rock923 · Joined: 25 Apr 2008 Posts: 4

Hi. Thanks for the quick reply.

Ok, so I need to typecast first in the callback function. However, it seems that the typecast is exactly what's causing the crash. I'm sort of wondering what's causing that.

gtk_dialog_run seems like a much cleaner idea. However, how can I have it also respond to the user pressing enter on the text entry.

I would really like to understand what I'm doing wrong with the callback, though.

Thanks,
Matt

Code: (C)

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char *
get_user_name()
{
GtkWidget *dialog;
GtkWidget *text;

dialog = gtk_dialog_new_with_buttons( "Name Entry",
NULL,
GTK_DIALOG_MODAL,
GTK_STOCK_OK,
GTK_RESPONSE_ACCEPT,
NULL );
text = gtk_entry_new( );

gtk_container_add( GTK_CONTAINER( GTK_DIALOG( dialog )->vbox ), text );
g_signal_connect( G_OBJECT(dialog),
"response",
G_CALLBACK(text_callback),
text );

gtk_widget_show_all( dialog );

return NULL;
}

void
text_callback( GtkWidget* w, gpointer data )
{
printf( "%s\n", gtk_entry_get_text( GTK_ENTRY( data ) ));
}

k_rock923 · Joined: 25 Apr 2008 Posts: 4

I figured it out. My prototype for the signal handler was wrong. d'oh!

Thanks for everyone's help :)