clapper-app: Add "Clear Queue" menu option

An option to clear playback queue from UI. This is quckier
and easier than manually dragging every item to bin.

Closes #434

src/bin/clapper-app/clapper-app-application.c

@@ -333,6 +333,23 @@ add_uri (GSimpleAction *action, GVariant *param, gpointer user_data)
   clapper_app_uri_dialog_open_uri (gtk_app);
 }
 
+static void
+clear_queue (GSimpleAction *action, GVariant *param, gpointer user_data)
+{
+  GtkApplication *gtk_app = GTK_APPLICATION (user_data);
+  GtkWindow *window = gtk_application_get_active_window (gtk_app);
+  ClapperPlayer *player;
+  ClapperQueue *queue;
+
+  while (window && !CLAPPER_APP_IS_WINDOW (window))
+    window = gtk_window_get_transient_for (window);
+
+  player = clapper_app_window_get_player (CLAPPER_APP_WINDOW (window));
+  queue = clapper_player_get_queue (player);
+
+  clapper_queue_clear (queue);
+}
+
 static void
 new_window (GSimpleAction *action, GVariant *param, gpointer user_data)
 {
@@ -692,6 +709,7 @@ clapper_app_application_constructed (GObject *object)
   static const GActionEntry app_actions[] = {
     { "add-files", add_files, NULL, NULL, NULL },
     { "add-uri", add_uri, NULL, NULL, NULL },
+    { "clear-queue", clear_queue, NULL, NULL, NULL },
     { "new-window", new_window, NULL, NULL, NULL },
     { "info", show_info, NULL, NULL, NULL },
     { "preferences", show_preferences, NULL, NULL, NULL },

src/bin/clapper-app/ui/clapper-app-queue-list.ui

@@ -183,5 +183,11 @@
         <attribute name="action">app.add-uri</attribute>
       </item>
     </section>
+    <section>
+      <item>
+        <attribute name="label" translatable="yes">Clear Queue</attribute>
+        <attribute name="action">app.clear-queue</attribute>
+      </item>
+    </section>
   </menu>
 </interface>