meson-tutorial-gtk: Add a button with click handler

Author: nh2

meson-tutorial-gtk/gtkmain.c

@@ -1,11 +1,22 @@
 #include <gtk/gtk.h>
 
+void button_event(GtkWidget *widget, gpointer *data) {
+  g_print("Button clicked\n");
+  gtk_button_set_label(GTK_BUTTON(widget), "It worked!");
+}
+
 int main(int argc, char **argv) {
   GtkWidget *win;
   gtk_init(&argc, &argv);
   win = gtk_window_new(GTK_WINDOW_TOPLEVEL);
   gtk_window_set_title(GTK_WINDOW(win), "Hello there");
   g_signal_connect(win, "destroy", G_CALLBACK(gtk_main_quit), NULL);
+
+  GtkWidget *button = gtk_button_new_with_mnemonic("_Click me!");
+  gtk_widget_show(button);
+  g_signal_connect(button, "pressed", G_CALLBACK(button_event), NULL);
+  gtk_container_add(GTK_CONTAINER(win), button);
+
   gtk_widget_show(win);
   gtk_main();
 }