Handle destroy_notify X events in manager

lib/uh/wm/manager.rb

@@ -109,6 +109,10 @@ module Uh
         configure event.window
       end
 
+      def handle_destroy_notify event
+        destroy event.window
+      end
+
       def handle_map_request event
         map event.window
       end

spec/uh/wm/manager_spec.rb

@@ -323,6 +323,15 @@ module Uh
           end
         end
 
+        context 'when destroy_notify event is given' do
+          let(:event) { double 'event', type: :destroy_notify, window: :window }
+
+          it 'destroy the event window' do
+            expect(manager).to receive(:destroy).with :window
+            manager.handle event
+          end
+        end
+
         context 'when map_request event is given' do
           let(:event) { double 'event', type: :map_request, window: :window }