[gnome-games] ui: Add Application.is_running_in_flatpak()

[Adrien Plazas <aplazas src gnome org>]

commit 13263da5788e4f442eab2970f633d9c516c876dd
Author: Alexander Mikhaylenko <exalm7659 gmail com>
Date:   Thu Aug 16 13:53:44 2018 +0500

    ui: Add Application.is_running_in_flatpak()
    
    This will be used in the following commits to special-case running host
    commands from sandbox.

 src/ui/application.vala | 13 +++++++++++++
 1 file changed, 13 insertions(+)
---
diff --git a/src/ui/application.vala b/src/ui/application.vala
index 49896258..b8c317ea 100644
--- a/src/ui/application.vala
+++ b/src/ui/application.vala
@@ -3,6 +3,8 @@
 public class Games.Application : Gtk.Application {
        const string HELP_URI = "https://wiki.gnome.org/Apps/Games/Documentation";;
 
+       private static bool? is_flatpak;
+
        private Database database;
 
        private PreferencesWindow preferences_window;
@@ -152,6 +154,17 @@ public class Games.Application : Gtk.Application {
                return @"$data_dir/medias";
        }
 
+       public static bool is_running_in_flatpak () {
+               if (is_flatpak != null)
+                       return is_flatpak;
+
+               var file = File.new_for_path ("/.flatpak-info");
+
+               is_flatpak = file.query_exists ();
+
+               return is_flatpak;
+       }
+
        public void add_game_files () {
                add_game_files_async.begin ();
        }