Oracle and Open Source

Programming with GTK+

Let’s take an initial look inside a GTK+-based application. We recommend that you download and install GTK+ first so you can try this out. If you have a recent version of Linux, you may already have GTK+ installed.

Sample Program

In this section, we’ll run through Example 9-1, a quick “Hello World” program that’s a simple demonstration of a one-button window. When you click the button, “Hello World” is printed to your shell, and then the program exits. We’ve highlighted the program elements we’ll describe later on.

Example 9-1. GTK+ helloworld.c

#include <gtk/gtk.h>

/* This is a callback function. The data arguments are ignored
 * in this example. More on callbacks below. */
void hello( GtkWidget *widget,
            gpointer   data )
{
   g_print ("Hello World\n");
}

gint delete_event( GtkWidget *widget,
                   GdkEvent  *event,
                   gpointer   data )
{
   /* If you return FALSE in the "delete_event" signal handler,
    * GTK will emit the "destroy" signal. Returning TRUE means
    * you don't want the window to be destroyed.
    * This is useful for popping up 'are you sure you want to quit?'
    * type dialogs. */

   g_print ("delete event occurred\n"); /* Change TRUE to FALSE and the main window will be destroyed with * a "delete_event". */ return(TRUE); } /* Another callback */ void destroy( GtkWidget *widget, gpointer data ) { gtk_main_quit( ); } int main( int argc, char *argv[] ) { /* GtkWidget is the storage type for widgets */ GtkWidget *window; GtkWidget *button; /* This is called in all GTK applications. ...