add OverlayAnimator interface. ViewerPanel has a list of OverlayAnimators.

ViwerPanel.addOverlayAnimator(animator) adds a new one.
When animator.isComplete() it is removed.

core/src/main/java/bdv/viewer/ViewerPanel.java

@@ -46,6 +46,7 @@ import bdv.img.cache.Cache;
 import bdv.util.Affine3DHelpers;
 import bdv.viewer.animate.AbstractTransformAnimator;
 import bdv.viewer.animate.MessageOverlayAnimator;
+import bdv.viewer.animate.OverlayAnimator;
 import bdv.viewer.animate.RotationAnimator;
 import bdv.viewer.animate.TextOverlayAnimator;
 import bdv.viewer.animate.TextOverlayAnimator.TextPosition;
@@ -145,9 +146,11 @@ public class ViewerPanel extends JPanel implements OverlayRenderer, TransformLis
 	protected AbstractTransformAnimator currentAnimator = null;
 
 	/**
-	 * Currently only used to show initial "press F1 for help" message.
+	 * A list of currently incomplete (see {@link OverlayAnimator#isComplete()})
+	 * animators. Initially, this contains a {@link TextOverlayAnimator} showing
+	 * the "press F1 for help" message.
 	 */
-	protected TextOverlayAnimator animatedOverlay;
+	protected ArrayList< OverlayAnimator > overlayAnimators;
 
 	/**
 	 * Fade-out overlay of recent messages. See {@link #showMessage(String)}.
@@ -305,7 +308,10 @@ public class ViewerPanel extends JPanel implements OverlayRenderer, TransformLis
 		transformListeners = new CopyOnWriteArrayList< TransformListener< AffineTransform3D > >();
 
 		msgOverlay = optional.msgOverlay;
-		animatedOverlay = new TextOverlayAnimator( "Press <F1> for help.", 3000, TextPosition.CENTER );
+
+		overlayAnimators = new ArrayList< OverlayAnimator >();
+		overlayAnimators.add( msgOverlay );
+		overlayAnimators.add( new TextOverlayAnimator( "Press <F1> for help.", 3000, TextPosition.CENTER ) );
 
 		display.addComponentListener( new ComponentAdapter()
 		{
@@ -407,23 +413,20 @@ public class ViewerPanel extends JPanel implements OverlayRenderer, TransformLis
 		g.setFont( new Font( "Monospaced", Font.PLAIN, 12 ) );
 		g.drawString( mousePosGlobalString, ( int ) g.getClipBounds().getWidth() - 170, 25 );
 
-		if ( animatedOverlay != null )
-		{
-			animatedOverlay.paint( ( Graphics2D ) g, System.currentTimeMillis() );
-			if ( animatedOverlay.isComplete() )
-				animatedOverlay = null;
-			else
-				display.repaint();
-		}
+		boolean requiresRepaint = multiBoxOverlayRenderer.isHighlightInProgress();
 
-		if ( !msgOverlay.isComplete() )
+		final long currentTimeMillis = System.currentTimeMillis();
+		final ArrayList< OverlayAnimator > overlayAnimatorsToRemove = new ArrayList< OverlayAnimator >();
+		for ( final OverlayAnimator animator : overlayAnimators )
 		{
-			msgOverlay.paint( ( Graphics2D ) g, System.currentTimeMillis() );
-			if ( !msgOverlay.isComplete() )
-				display.repaint();
+			animator.paint( ( Graphics2D ) g, currentTimeMillis );
+			requiresRepaint |= animator.requiresRepaint();
+			if ( animator.isComplete() )
+				overlayAnimatorsToRemove.add( animator );
 		}
+		overlayAnimators.removeAll( overlayAnimatorsToRemove );
 
-		if ( multiBoxOverlayRenderer.isHighlightInProgress() )
+		if ( requiresRepaint )
 			display.repaint();
 	}
 
@@ -636,6 +639,20 @@ public class ViewerPanel extends JPanel implements OverlayRenderer, TransformLis
 		display.repaint();
 	}
 
+	/**
+	 * Add a new {@link OverlayAnimator} to the list of animators. The animation
+	 * is immediately started. The new {@link OverlayAnimator} will remain in
+	 * the list of animators until it {@link OverlayAnimator#isComplete()}.å
+	 *
+	 * @param animator
+	 *            animator to add.
+	 */
+	public void addOverlayAnimator( final OverlayAnimator animator )
+	{
+		overlayAnimators.add( animator );
+		display.repaint();
+	}
+
 	/**
 	 * Add a {@link TransformListener} to notify about viewer transformation
 	 * changes. Listeners will be notified <em>before</em> calling

core/src/main/java/bdv/viewer/animate/AbstractAnimator.java

@@ -12,7 +12,7 @@ import bdv.viewer.ViewerFrame;
  * @author Tobias Pietzsch <tobias.pietzsch@gmail.com>
  * @author Jean-Yves Tinevez <jeanyves.tinevez@gmail.com>
  */
-public abstract class AbstractAnimator
+public class AbstractAnimator
 {
 	/** Expected duration length of the animation (in time units). */
 	private final long duration;

core/src/main/java/bdv/viewer/animate/MessageOverlayAnimator.java

@@ -17,7 +17,7 @@ import java.util.List;
  *
  * @author Tobias Pietzsch <tobias.pietzsch@gmail.com>
  */
-public class MessageOverlayAnimator
+public class MessageOverlayAnimator implements OverlayAnimator
 {
 	protected static class TextAnimator extends AbstractAnimator
 	{
@@ -64,14 +64,24 @@ public class MessageOverlayAnimator
 		texts.add( 0, new TextAnimator( text, duration ) );
 	}
 
+	@Override
 	public boolean isComplete()
 	{
-		return texts.isEmpty();
+		// We this animator should not be removed, ever.
+		return false;
 	}
 
+
+	@Override
+	public boolean requiresRepaint()
+	{
+		return !texts.isEmpty();
+	}
+
+	@Override
 	public void paint( final Graphics2D g, final long time )
 	{
-		if ( isComplete() )
+		if ( !requiresRepaint() )
 			return;
 
 		final double ox = g.getClipBounds().getWidth() - 10;

core/src/main/java/bdv/viewer/animate/OverlayAnimator.java

+package bdv.viewer.animate;
+
+import java.awt.Graphics2D;
+
+public interface OverlayAnimator
+{
+	public abstract void paint( final Graphics2D g, final long time );
+
+	/**
+	 * Returns true if the animation is complete and the animator can be
+	 * removed.
+	 *
+	 * @return whether the animation is complete and the animator can be
+	 *         removed.
+	 */
+	public boolean isComplete();
+
+	/**
+	 * Returns true if the animator requires an immediate repaint to continue
+	 * the animation.
+	 *
+	 * @return whetherhe animator requires an immediate repaint.
+	 */
+	public boolean requiresRepaint();
+}

core/src/main/java/bdv/viewer/animate/TextOverlayAnimator.java

@@ -13,7 +13,7 @@ import java.awt.geom.Rectangle2D;
  *
  * @author Tobias Pietzsch <tobias.pietzsch@gmail.com>
  */
-public class TextOverlayAnimator extends AbstractAnimator
+public class TextOverlayAnimator extends AbstractAnimator implements OverlayAnimator
 {
 	protected final Font font;
 
@@ -56,6 +56,7 @@ public class TextOverlayAnimator extends AbstractAnimator
 		this.position = position;
 	}
 
+	@Override
 	public void paint( final Graphics2D g, final long time )
 	{
 		setTime( time );
@@ -87,4 +88,10 @@ public class TextOverlayAnimator extends AbstractAnimator
 		g.setColor( new Color( 1f, 1f, 1f, alpha ) );
 		layout.draw( g, x, y );
 	}
+
+	@Override
+	public boolean requiresRepaint()
+	{
+		return !isComplete();
+	}
 }