fire event when source document tabs are activated

src/gwt/src/org/rstudio/studio/client/workbench/views/source/Source.java

@@ -2985,6 +2985,11 @@ public void onSelection(SelectionEvent<Integer> event)
       {
          activeEditor_ = editors_.get(event.getSelectedItem());
          activeEditor_.onActivate();
+
+         // let any listeners know this tab was activated
+         events_.fireEvent(new DocTabActivatedEvent(activeEditor_.getPath(), 
+               activeEditor_.getId()));
+
          // don't send focus to the tab if we're expecting a debug selection
          // event
          if (initialized_ && !isDebugSelectionPending())

src/gwt/src/org/rstudio/studio/client/workbench/views/source/events/DocTabActivatedEvent.java

@@ -0,0 +1,70 @@
+/*
+ * DocTabActivatedEvent.java
+ *
+ * Copyright (C) 2009-15 by RStudio, Inc.
+ *
+ * Unless you have received this program directly from RStudio pursuant
+ * to the terms of a commercial license agreement with RStudio, then
+ * this program is licensed to you under the terms of version 3 of the
+ * GNU Affero General Public License. This program is distributed WITHOUT
+ * ANY EXPRESS OR IMPLIED WARRANTY, INCLUDING THOSE OF NON-INFRINGEMENT,
+ * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Please refer to the
+ * AGPL (http://www.gnu.org/licenses/agpl-3.0.txt) for more details.
+ *
+ */
+
+package org.rstudio.studio.client.workbench.views.source.events;
+
+import org.rstudio.core.client.js.JavaScriptSerializable;
+import org.rstudio.studio.client.application.events.CrossWindowEvent;
+
+import com.google.gwt.event.shared.EventHandler;
+import com.google.gwt.event.shared.GwtEvent;
+
+@JavaScriptSerializable
+public class DocTabActivatedEvent 
+             extends CrossWindowEvent<DocTabActivatedEvent.Handler>
+{ 
+   public interface Handler extends EventHandler
+   {
+      void onDocTabActivated(DocTabActivatedEvent event);
+   }
+
+   public static final GwtEvent.Type<DocTabActivatedEvent.Handler> TYPE =
+      new GwtEvent.Type<DocTabActivatedEvent.Handler>();
+
+   public DocTabActivatedEvent()
+   {
+   }
+
+   public DocTabActivatedEvent(String path, String id)
+   {
+      path_ = path;
+      id_ = id;
+   }
+
+   public String getPath()
+   {
+      return path_;
+   }
+
+   public String getId()
+   {
+      return id_;
+   }
+
+   @Override
+   protected void dispatch(DocTabActivatedEvent.Handler handler)
+   {
+      handler.onDocTabActivated(this);
+   }
+
+   @Override
+   public GwtEvent.Type<DocTabActivatedEvent.Handler> getAssociatedType()
+   {
+      return TYPE;
+   }
+
+   private String path_;
+   private String id_;
+}