1. Open a Window

First we make a quick 'Hello, World!' program. To make sure our environment is set up and working.

File: main.c

#include <gtk/gtk.h>

int main(int argc, char *argv[]) {

   GtkWidget *window;

   gtk_init(&argc, &argv);

   window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
   gtk_window_set_title(GTK_WINDOW(window), "Brickout Tutorial");
   gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);
   gtk_window_set_default_size(GTK_WINDOW(window), 640, 480);
   gtk_window_set_type_hint(GTK_WINDOW(window), GDK_WINDOW_TYPE_HINT_UTILITY);
   g_signal_connect(window, "destroy", G_CALLBACK(gtk_main_quit), NULL);

   gtk_widget_show_all(window);

   gtk_main();

   return 0;

}

While there's not much going here, let's try to break down and identify what is happening. I would imagine that most of the syntax here is self-explanitory, but I will try none-the-less. We create a new window with gtk_window_new. We then give the window a title with gtk_window_set_title. We then define where we want the window to appear on the screen initialially. Where we are using GTK_WIN_POS_CENTER, but we will list the other options below.

Name	Description
GTK_WIN_POS_NONE	No influence is made on placement.
GTK_WIN_POS_CENTER	Windows should be placed in the center of the screen.
GTK_WIN_POS_MOUSE	Windows should be placed at the current mouse position.
GTK_WIN_POS_CENTER_ALWAYS	Keep window centered as it changes size, etc.
GTK_WIN_POS_CENTER_ON_PARENT	Center the window on its transient parent (see gtk_window_set_transient_for())

So basically for an application like this, center makes the most sense. After that we have a function to set the hint type. In most cases, this isn't actually needed. This is for added for tiling desktop environments such as i3 to keep our application from stretching.

We call g_signal_connect to completely exit out of the application once the window has been closed. Since GTK doesn't completely exit the process when the window is closed. We call gtk_widget_show_all to show the window to the user, and then we call gtk_main to start the application.

Compile

$ gcc `pkg-config --cflags gtk+-3.0` main.c `pkg-config --libs gtk+-3.0`

Run:

./a.out