On Thu, 3 May 2007, beginner.c wrote:
I know how to pass by reference in C normally. But how do I pass by ref a
GTK Widget to a function?
The same way, by giving the address of the object. However, with
a GtkWidget what you have in hand is already a pointer so in most
cases it suffices to pass that pointer.
Totally useless but hopefully illustrative code follows:
#include gtk/gtk.h
void f1 (GtkWidget *w)
{
gtk_widget_show(w);
gtk_widget_destroy(w);
}
void f2 (GtkWidget **pw)
{
gtk_widget_show(*pw);
gtk_widget_destroy(*pw);
*pw = NULL;
}
int main (int argc, char **argv)
{
GtkWidget *w;
gtk_init(argc, argv);
w = gtk_window_new(GTK_WINDOW_TOPLEVEL);
printf(created new GtkWidget at %p\n, (void *) w);
f1(w);
/* bzzt, invalid pointer below; it has been freed */
printf(After f1(), w = %p\n, (void *) w);
w = gtk_window_new(GTK_WINDOW_TOPLEVEL);
printf(created new GtkWidget at %p\n, (void *) w);
f2(w);
printf(After f2(), w = %p\n, (void *) w);
return 0;
}
Here, the above prints:
created new GtkWidget at 0x8079000
After f1(), w = 0x8079000
created new GtkWidget at 0x80790a8
After f2(), w = (nil)
Allin Cottrell
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