Actually the 3 elements in newstr[] are the same, i.e. tmpstr, because tmpstr is an array, it has fixed address in this routine. Therefore when you pass the address to G_CALLBACK (button_cb) in g_signal_connect, the content is still right, say "1", "2" and "3". But after the "for" loop, the content is "3", and all reference to this address is "3".
Maybe this could be better:
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <gtk/gtk.h>
static void button_cb (GtkWidget *widget, gpointer data)
{
g_print ("Hello - %s was pressed\n", (gchar *) data);
}
static void delete_event_cb(GtkWidget *widget, GdkEvent *event, gpointer
data)
{
g_print ("A delete event has occurred\n");
gtk_main_quit();
}
int main( int argc,
char *argv[] )
{
GtkWidget *window;
GtkWidget *button;
GtkWidget *box1;
gchar *newstr[3];
//gchar tmpstr[12];
gchar *tmpstr;
gint i;
gtk_init (&argc, &argv);
window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
gtk_window_set_title (GTK_WINDOW (window), "Test Program");
gtk_container_set_border_width (GTK_CONTAINER (window), 50);
g_signal_connect (G_OBJECT (window), "delete_event", G_CALLBACK (delete_event_cb), NULL);
box1 = gtk_hbox_new (TRUE, 20);
gtk_container_add (GTK_CONTAINER (window), box1);
for (i=1; i<=3; i=i+1)
{
tmpstr = (gchar *)g_malloc0(12);
sprintf(tmpstr,"%s%d","Button ",i);
printf("The value of tmpstr = %s\n",tmpstr); /* Prints
Button 1, Button 2, Button 3*/
newstr[i-1] = tmpstr;
printf("The current label is %s\n",newstr[i-1]); /* Prints
Button 1, Button 2, Button 3*/
button = gtk_button_new_with_label (newstr[i-1]);
g_signal_connect (G_OBJECT (button), "clicked", G_CALLBACK (button_cb), (gpointer) newstr[i-1]);
gtk_box_pack_start (GTK_BOX(box1), button, TRUE, TRUE, 0);
gtk_widget_show (button);
printf("The current label is %s\n",newstr[i-1]); /* Prints Button 1, Button 2, Button 3*/
}
printf("The value of element 1 is %s\n",newstr[0]); /* Prints Button 3*/
printf("The value of element 2 is %s\n",newstr[1]); /* Prints Button 3*/
printf("The value of element 3 is %s\n",newstr[2]); /* Prints Button 3*/
gtk_widget_show (box1);
gtk_widget_show (window);
gtk_main ();
return 0;
}
---------------------------------------
Best Wishes!
Zhang Hui
Email: Hui003.Zhang@xxxxxxxxxxx
Phone: 86-25-58748787-8215
Samsung Electronics(China) R&D Center
---------------------------------------
-----Original Message-----
From: gtk-list-bounces@xxxxxxxxx [mailto:gtk-list-bounces@xxxxxxxxx] On Behalf Of Chris
Sent: Thursday, November 30, 2006 9:31 AM
To: gtklist
Subject: Problem with Data Passed to Call Back Function
Hello,
In the program below I am creating 3 buttons in a
horizontal box. The buttons get created and labeled
properly as:
Button 1
Button 2
Button 3
When I click on any of the buttons though,
the data sent to the callback function should
be the label of the button pressed.
Instead it all shows up as:
Button 3
The button labels are stored in an array of character
pointers which appears to work find in the for loop.
Once out, if I print out the contents of the array
of character pointers they are all:
Button 3
I am guessing that I am missing some simple
problem but have been unable to find it on
my own.
Any help would be appreciated.
Thanks
Chris
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <gtk/gtk.h>
static void button_cb (GtkWidget *widget, gpointer data)
{
g_print ("Hello - %s was pressed\n", (gchar *) data);
}
static void delete_event_cb(GtkWidget *widget, GdkEvent *event, gpointer
data)
{
g_print ("A delete event has occurred\n");
gtk_main_quit();
}
int main( int argc,
char *argv[] )
{
GtkWidget *window;
GtkWidget *button;
GtkWidget *box1;
gchar *newstr[3];
gchar tmpstr[12];
gint i;
gtk_init (&argc, &argv);
window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
gtk_window_set_title (GTK_WINDOW (window), "Test Program");
gtk_container_set_border_width (GTK_CONTAINER (window), 50);
g_signal_connect (G_OBJECT (window), "delete_event", G_CALLBACK
(delete_event_cb), NULL);
box1 = gtk_hbox_new (TRUE, 20);
gtk_container_add (GTK_CONTAINER (window), box1);
for (i=1; i<=3; i=i+1)
{
sprintf(tmpstr,"%s%d","Button ",i);
printf("The value of tmpstr = %s\n",tmpstr); /* Prints
Button 1, Button 2, Button 3*/
newstr[i-1] = tmpstr;
printf("The current label is %s\n",newstr[i-1]); /* Prints
Button 1, Button 2, Button 3*/
button = gtk_button_new_with_label (newstr[i-1]);
g_signal_connect (G_OBJECT (button), "clicked", G_CALLBACK
(button_cb), (gpointer) newstr[i-1]);
gtk_box_pack_start (GTK_BOX(box1), button, TRUE, TRUE, 0);
gtk_widget_show (button);
printf("The current label is %s\n",newstr[i-1]); /* Prints
Button 1, Button 2, Button 3*/
}
printf("The value of element 1 is %s\n",newstr[0]); /*
Prints Button 3*/
printf("The value of element 2 is %s\n",newstr[1]); /*
Prints Button 3*/
printf("The value of element 3 is %s\n",newstr[2]); /*
Prints Button 3*/
gtk_widget_show (box1);
gtk_widget_show (window);
gtk_main ();
return 0;
}
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