[gnome-robots] Fix dragging the window after clicking the game view

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 3b170cc59a0ce32f2a7f56fd7ac040a2f3a61d0d
Author: Michael Catanzaro <mcatanzaro gnome org>
Date:   Fri Sep 11 12:29:47 2015 -0500

    Fix dragging the window after clicking the game view
    
    https://bugzilla.gnome.org/show_bug.cgi?id=754837

 src/gnome-robots.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/gnome-robots.c b/src/gnome-robots.c
index f89273a..9b5e567 100644
--- a/src/gnome-robots.c
+++ b/src/gnome-robots.c
@@ -338,7 +338,7 @@ activate (GtkApplication *app, gpointer user_data)
   make_cursors ();
 
   game_area = gtk_drawing_area_new ();
-  gtk_widget_add_events (game_area, GDK_BUTTON_PRESS_MASK |
+  gtk_widget_add_events (game_area, GDK_BUTTON_PRESS_MASK | GDK_BUTTON_RELEASE_MASK |
                         GDK_POINTER_MOTION_MASK);
   g_signal_connect (G_OBJECT (game_area), "button-press-event",
                    G_CALLBACK (mouse_cb), NULL);