[gnome-games] ui: Bind on_display_back() to Alt+Left/Right

[Adrien Plazas <aplazas src gnome org>]

commit a0e49546332339b444c20d356ce4c6ec4a7d0869
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Fri Dec 1 15:07:56 2017 +0100

    ui: Bind on_display_back() to Alt+Left/Right
    
    Go back from the game display to the collection by pressing Alt+Left on
    left-to-right text direction or Alt+Right on right-to-left text
    direction.

 src/ui/application-window.vala | 8 ++++++++
 1 file changed, 8 insertions(+)
---
diff --git a/src/ui/application-window.vala b/src/ui/application-window.vala
index 4c157ef..4ea906d 100644
--- a/src/ui/application-window.vala
+++ b/src/ui/application-window.vala
@@ -513,6 +513,14 @@ private class Games.ApplicationWindow : Gtk.ApplicationWindow {
                        return true;
                }
 
+               if (((event.state & default_modifiers) == Gdk.ModifierType.MOD1_MASK) &&
+                   (((get_direction () == Gtk.TextDirection.LTR) && event.keyval == Gdk.Key.Left) ||
+                    ((get_direction () == Gtk.TextDirection.RTL) && event.keyval == Gdk.Key.Right))) {
+                       on_display_back ();
+
+                       return true;
+               }
+
                return false;
        }