Let UI fire PollEvents (#12466)

Change-Id: I7eb5e407b6822f5b3ac8e103ba7c9f676c51648f

2 files changed, 133 insertions, 5 deletions

diff --git a/server/src/com/vaadin/event/UIEvents.java b/server/src/com/vaadin/event/UIEvents.java
new file mode 100644
index 0000000000..321bfc9251
--- /dev/null
+++ b/server/src/com/vaadin/event/UIEvents.java
@@ -0,0 +1,116 @@
+/*
+ * Copyright 2000-2013 Vaadin Ltd.
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ * 
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.event;
+
+import java.io.Serializable;
+import java.lang.reflect.Method;
+
+import com.vaadin.ui.Component;
+import com.vaadin.ui.UI;
+import com.vaadin.util.ReflectTools;
+
+/**
+ * A class that contains events, listeners and handlers specific to the
+ * {@link UI} class.
+ * 
+ * @since 7.2
+ * @author Vaadin Ltd
+ */
+public interface UIEvents {
+
+    /**
+     * A {@link PollListener} receives and handles {@link PollEvent PollEvents}
+     * fired by {@link PollNotifier PollNotifiers}.
+     * 
+     * @since 7.2
+     * @author Vaadin Ltd
+     */
+    public interface PollListener extends Serializable {
+        public static final Method POLL_METHOD = ReflectTools.findMethod(
+                PollListener.class, "poll", PollEvent.class);
+
+        /**
+         * A poll request has been received by the server.
+         * 
+         * @param event
+         *            poll event
+         */
+        public void poll(PollEvent event);
+    }
+
+    /**
+     * An event that is fired whenever a client polls the server for
+     * asynchronous UI updates.
+     * 
+     * @since 7.2
+     * @author Vaadin Ltd
+     */
+    public static class PollEvent extends Component.Event {
+        public PollEvent(UI ui) {
+            super(ui);
+        }
+
+        /**
+         * Get the {@link UI} instance that received the poll request.
+         * 
+         * @return the {@link UI} that received the poll request. Never
+         *         <code>null</code>.
+         */
+        public UI getUI() {
+            /*
+             * This cast is safe to make, since this class' constructor
+             * constrains the source to be a UI instance.
+             */
+            return (UI) getComponent();
+        }
+    }
+
+    /**
+     * The interface for adding and removing {@link PollEvent} listeners.
+     * <p>
+     * By implementing this interface, a class publicly announces that it is
+     * able to send {@link PollEvent PollEvents} whenever the client sends a
+     * periodic poll message to the client, to check for asynchronous
+     * server-side modifications.
+     * 
+     * @since 7.2
+     * @see UI#setPollInterval(int)
+     */
+    public interface PollNotifier extends Serializable {
+        /**
+         * Add a poll listener.
+         * <p>
+         * The listener is called whenever the client polls the server for
+         * asynchronous UI updates.
+         * 
+         * @see UI#setPollInterval(int)
+         * @see #removePollListener(PollListener)
+         * @param listener
+         *            the {@link PollListener} to add
+         */
+        public void addPollListener(PollListener listener);
+
+        /**
+         * Remove a poll listener.
+         * 
+         * @see #addPollListener(PollListener)
+         * @param listener
+         *            the listener to be removed
+         */
+        public void removePollListener(PollListener listener);
+    }
+
+}
diff --git a/server/src/com/vaadin/ui/UI.java b/server/src/com/vaadin/ui/UI.java
index 0d2ef4d569..a292e6b829 100644
--- a/server/src/com/vaadin/ui/UI.java
+++ b/server/src/com/vaadin/ui/UI.java
@@ -32,6 +32,9 @@ import com.vaadin.event.Action.Handler;
 import com.vaadin.event.ActionManager;
 import com.vaadin.event.MouseEvents.ClickEvent;
 import com.vaadin.event.MouseEvents.ClickListener;
+import com.vaadin.event.UIEvents.PollEvent;
+import com.vaadin.event.UIEvents.PollListener;
+import com.vaadin.event.UIEvents.PollNotifier;
 import com.vaadin.navigator.Navigator;
 import com.vaadin.server.ClientConnector;
 import com.vaadin.server.ComponentSizeValidator;
@@ -95,7 +98,8 @@ import com.vaadin.util.CurrentInstance;
  * @since 7.0
  */
 public abstract class UI extends AbstractSingleComponentContainer implements
-        Action.Container, Action.Notifier, LegacyComponent, Focusable {
+        Action.Container, Action.Notifier, PollNotifier, LegacyComponent,
+        Focusable {
 
     /**
      * The application to which this UI belongs
@@ -167,10 +171,7 @@ public abstract class UI extends AbstractSingleComponentContainer implements
 
         @Override
         public void poll() {
-            /*
-             * No-op. This is only called to cause a server visit to check for
-             * changes.
-             */
+            fireEvent(new PollEvent(UI.this));
         }
     };
     private DebugWindowServerRpc debugRpc = new DebugWindowServerRpc() {
@@ -1490,6 +1491,17 @@ public abstract class UI extends AbstractSingleComponentContainer implements
         return getState(false).pollInterval;
     }
 
+    @Override
+    public void addPollListener(PollListener listener) {
+        addListener(EventId.POLL, PollEvent.class, listener,
+                PollListener.POLL_METHOD);
+    }
+
+    @Override
+    public void removePollListener(PollListener listener) {
+        removeListener(EventId.POLL, PollEvent.class, listener);
+    }
+
     /**
      * Retrieves the object used for configuring the push channel.
      *