App: add about(), prefs() and quit() methods

These methods were previously part of the AppEventService, but make more
sense as App-specific methods. That way, each app can control the way it
handles these functions.

Another important consequence of this change is that we no longer need
multiple AppEventService implementations competing to define the
behavior of these three operations.

This avoids a cascade/domino problem where AppEventService is a
SciJavaService, but individual apps like ImageJ2 override behavior with
e.g. LegacyAppEventService which pulls in lots of IJ2 dependencies into
a "SciJava-only" context.

By making it handled at the plugin level, we avoid the issue because
those plugins simply fail to initialize as desired when the required
services are unavailable to the context.

Author: ctrueden

src/main/java/org/scijava/app/AbstractApp.java

@@ -33,7 +33,9 @@
 
 import java.io.File;
 
+import org.scijava.log.LogService;
 import org.scijava.plugin.AbstractRichPlugin;
+import org.scijava.plugin.Parameter;
 import org.scijava.util.AppUtils;
 import org.scijava.util.Manifest;
 import org.scijava.util.POM;
@@ -45,6 +47,9 @@
  */
 public abstract class AbstractApp extends AbstractRichPlugin implements App {
 
+	@Parameter(required = false)
+	private LogService log;
+
 	/** Maven POM with metadata about the application. */
 	private POM pom;
 
@@ -108,4 +113,19 @@ public File getBaseDirectory() {
 		return AppUtils.getBaseDirectory(getSystemProperty(), getClass(), null);
 	}
 
+	@Override
+	public void about() {
+		if (log != null) log.info(getInfo(false));
+	}
+
+	@Override
+	public void prefs() {
+		// NB: Do nothing.
+	}
+
+	@Override
+	public void quit() {
+		getContext().dispose();
+	}
+
 }

src/main/java/org/scijava/app/App.java

@@ -96,6 +96,24 @@ public interface App extends RichPlugin, SingletonPlugin, Versioned {
 	 */
 	File getBaseDirectory();
 
+	/**
+	 * Displays information about the application. Typically this action
+	 * takes the form as About dialog in the UI, and/or a message on the console.
+	 */
+	void about();
+
+	/**
+	 * Displays application preferences. The behavior is application-specific, but
+	 * typically a preferences dialog will be shown onscreen.
+	 */
+	void prefs();
+
+	/**
+	 * Quits the application. Typically this action will prompt the user about any
+	 * unsaved work first.
+	 */
+	void quit();
+
 	// -- Versioned methods --
 
 	/**