Created a mechanism for dispatching notifications to user interface

elements when the client enters and leaves a place.


git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@394 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/java/com/threerings/crowd/client/PlaceView.java

@@ -0,0 +1,58 @@
+//
+// $Id: PlaceView.java,v 1.1 2001/10/04 20:02:49 mdb Exp $
+
+package com.threerings.cocktail.party.util;
+
+import com.threerings.cocktail.party.data.PlaceObject;
+
+/**
+ * This interface provides a convenient means for decoupling user
+ * interface components that interact with a place object and that need to
+ * keep themselves up to date when the client moves from place to place.
+ *
+ * <p> In general, such components need to know when the client is about
+ * to enter a place so that they can subscribe if necessary or at least
+ * extract information about the place. They also need to know when a
+ * client has left a place so that they can unsubscribe and clean up after
+ * themselves. This is the information that the place view interface makes
+ * available to them in a decoupled way.
+ *
+ * <p> The part of the client implementation that is responsible for the
+ * main user interface can act as a location observer, and it can make use
+ * of {@link PlaceViewUtil} to dispatch notification of place changes to
+ * every <code>PlaceView</code> implementing user interface element in the
+ * user interface hierarchy with calls to {@link
+ * PlaceViewUtil#dispatchWillEnterPlace} and {@link
+ * PlaceViewUtil#dispatchDidLeavePlace}. These functions traverse the UI
+ * hierarchy (starting with the element provided which would generally be
+ * the top-level UI element, and dispatch calls to {@link #willEnterPlace}
+ * and {@link #willLeavePlace} respectively on any UI element they find
+ * that implements <code>PlaceView</code>.
+ *
+ * <p> By doing this, the client code can simply create place-sensitive
+ * user interface elements and stick them in the user interface and
+ * essentially forget about them, knowing that they will all be notified
+ * of place entering and exiting by virtue of the single dispatching
+ * calls. It is useful to note that place-sensitive user interface
+ * elements will also generally need a reference to the {@link
+ * PartyContext} derivative in use by the client, but those are best
+ * supplied at construct time.
+ */
+public interface PlaceView
+{
+    /**
+     * Called when the client has entered a place and is about to display
+     * the user interface for that place.
+     *
+     * @param plobj the place object that was just entered.
+     */
+    public void willEnterPlace (PlaceObject plobj);
+
+    /**
+     * Called after the client has left a place and needs to clean up
+     * after the user interface that was displaying that place.
+     *
+     * @param plobj the place object that was just left.
+     */
+    public void didLeavePlace (PlaceObject plobj);
+}

src/java/com/threerings/crowd/client/PlaceViewUtil.java

@@ -0,0 +1,85 @@
+//
+// $Id: PlaceViewUtil.java,v 1.1 2001/10/04 20:02:49 mdb Exp $
+
+package com.threerings.cocktail.party.util;
+
+import java.awt.Component;
+import java.awt.Container;
+
+import com.threerings.cocktail.party.Log;
+import com.threerings.cocktail.party.data.PlaceObject;
+
+/**
+ * Provides a mechanism for dispatching notifications to all user
+ * interface elements in a hierarchy that implement the {@link PlaceView}
+ * interface. Look at the documentation for {@link PlaceView} for more
+ * explanation.
+ */
+public class PlaceViewUtil
+{
+    /**
+     * Dispatches a call to {@link PlaceView#willEnterPlace} to all UI
+     * elements in the hierarchy rooted at the component provided via the
+     * <code>root</code> parameter.
+     *
+     * @param root the component at which to start traversing the UI
+     * hierarchy.
+     * @param plobj the place object that is about to be entered.
+     */
+    public static void dispatchWillEnterPlace (
+        Component root, PlaceObject plobj)
+    {
+        // dispatch the call on this component if it implements PlaceView
+        if (root instanceof PlaceView) {
+            try {
+                ((PlaceView)root).willEnterPlace(plobj);
+            } catch (Exception e) {
+                Log.warning("Component choked on willEnterPlace() " +
+                            "[component=" + root + ", plobj=" + plobj + "].");
+                Log.logStackTrace(e);
+            }
+        }
+
+        // now traverse all of this component's children
+        if (root instanceof Container) {
+            Container cont = (Container)root;
+            int ccount = cont.getComponentCount();
+            for (int i = 0; i < ccount; i++) {
+                dispatchWillEnterPlace(cont.getComponent(i), plobj);
+            }
+        }
+    }
+
+    /**
+     * Dispatches a call to {@link PlaceView#didLeavePlace} to all UI
+     * elements in the hierarchy rooted at the component provided via the
+     * <code>root</code> parameter.
+     *
+     * @param root the component at which to start traversing the UI
+     * hierarchy.
+     * @param plobj the place object that is about to be entered.
+     */
+    public static void dispatchDidLeavePlace (
+        Component root, PlaceObject plobj)
+    {
+        // dispatch the call on this component if it implements PlaceView
+        if (root instanceof PlaceView) {
+            try {
+                ((PlaceView)root).didLeavePlace(plobj);
+            } catch (Exception e) {
+                Log.warning("Component choked on didLeavePlace() " +
+                            "[component=" + root + ", plobj=" + plobj + "].");
+                Log.logStackTrace(e);
+            }
+        }
+
+        // now traverse all of this component's children
+        if (root instanceof Container) {
+            Container cont = (Container)root;
+            int ccount = cont.getComponentCount();
+            for (int i = 0; i < ccount; i++) {
+                dispatchDidLeavePlace(cont.getComponent(i), plobj);
+            }
+        }
+    }
+}