DisplayService: add a createDisplayQuietly method

This method creates a display without publishing a DisplayCreatedEvent.
It is the caller's responsibility to deal with ramifications of that.

This method is introduced to maintain backwards compatibility with the
old behavior. The display framework will probably be substantially
redesigned soon, at which point all of this will become moot. But in the
meantime, it is handy to be able to create a display without showing it.

This commit is dedicated to Richard Domander!

Author: ctrueden

src/main/java/org/scijava/display/DefaultDisplayService.java

@@ -209,6 +209,15 @@ public Display<?> createDisplay(final Object o) {
 
 	@Override
 	public Display<?> createDisplay(final String name, final Object o) {
+		final Display<?> display = createDisplayQuietly(o);
+		if (display == null) return null;
+		if (name != null) display.setName(name);
+		eventService.publish(new DisplayCreatedEvent(display));
+		return display;
+	}
+
+	@Override
+	public Display<?> createDisplayQuietly(final Object o) {
 		// get available display plugins from the plugin service
 		final List<PluginInfo<Display<?>>> displayPlugins = getDisplayPlugins();
 
@@ -219,8 +228,6 @@ public Display<?> createDisplay(final String name, final Object o) {
 			// TODO: how to handle multiple matches? prompt user with dialog box?
 			if (display.canDisplay(o)) {
 				display.display(o);
-				if (name != null) display.setName(name);
-				eventService.publish(new DisplayCreatedEvent(display));
 				return display;
 			}
 		}

src/main/java/org/scijava/display/DisplayService.java

@@ -123,6 +123,10 @@ <DT extends Display<?>> List<PluginInfo<DT>> getDisplayPluginsOfType(
 	 * <li>The {@link ObjectService} will add the new display to its index, until
 	 * a corresponding {@link DisplayDeletedEvent} is later published.</li>
 	 * </ul>
+	 * <p>
+	 * To create a {@link Display} without publishing an event, see
+	 * {@link #createDisplayQuietly}.
+	 * </p>
 	 * 
 	 * @param o The object for which a display should be created. The object is
 	 *          then added to the display.
@@ -144,6 +148,10 @@ <DT extends Display<?>> List<PluginInfo<DT>> getDisplayPluginsOfType(
 	 * <li>The {@link ObjectService} will add the new display to its index, until
 	 * a corresponding {@link DisplayDeletedEvent} is later published.</li>
 	 * </ul>
+	 * <p>
+	 * To create a {@link Display} without publishing an event, see
+	 * {@link #createDisplayQuietly}.
+	 * </p>
 	 * 
 	 * @param name The name to be assigned to the display.
 	 * @param o The object for which a display should be created. The object is
@@ -158,4 +166,21 @@ <DT extends Display<?>> List<PluginInfo<DT>> getDisplayPluginsOfType(
 	 */
 	Display<?> createDisplay(String name, Object o);
 
+	/**
+	 * Creates a display for the given object, without publishing a
+	 * {@link DisplayCreatedEvent}. Hence, the display will not be automatically
+	 * shown or tracked.
+	 * 
+	 * @param o The object for which a display should be created. The object is
+	 *          then added to the display.
+	 * @return Newly created {@code Display<?>} containing the given object. The
+	 *         Display is typed with ? rather than T matching the Object because
+	 *         it is possible for the Display to be a collection of some other
+	 *         sort of object than the one being added. For example, ImageDisplay
+	 *         is a {@code Display<DataView>} with the DataView wrapping a
+	 *         Dataset, yet the ImageDisplay supports adding Datasets directly,
+	 *         taking care of wrapping them in a DataView as needed.
+	 */
+	Display<?> createDisplayQuietly(Object o);
+
 }