[cooja] plugins/Visualizer: Multi-mote selection functionality

This adds multi-mote selection capabilities to the visualizer plugin:

- [Ctrl + Mouse Drag]: Rectangular selection of multiple motes
- [Ctrl + Mouse Click]: Add/Remove motes from current selection
- Mouse Drag on any selected Mote: Move all currently selected motes

Note: This changes previous behaviour of using Ctrl key.

tools/cooja/apps/mrm/java/org/contikios/mrm/MRMVisualizerSkin.java

@@ -33,6 +33,7 @@ import java.awt.Color;
 import java.awt.FontMetrics;
 import java.awt.Graphics;
 import java.awt.Point;
+import java.util.Set;
 
 import org.apache.log4j.Logger;
 
@@ -72,20 +73,23 @@ public class MRMVisualizerSkin implements VisualizerSkin {
   }
 
   public Color[] getColorOf(Mote mote) {
-    Mote selectedMote = visualizer.getSelectedMote();
+    if (visualizer.getSelectedMotes().contains(mote)) {
-    if (mote == selectedMote) {
       return new Color[] { Color.CYAN };
     }
     return null;
   }
 
   public void paintBeforeMotes(Graphics g) {
-    final Mote selectedMote = visualizer.getSelectedMote();
+    Set<Mote> selectedMotes = visualizer.getSelectedMotes();
-    if (simulation == null
+    if (simulation == null || selectedMotes == null || selectedMotes.isEmpty()) {
-        || selectedMote == null
-        || selectedMote.getInterfaces().getRadio() == null) {
       return;
     }
+    
+    final Mote selectedMote = visualizer.getSelectedMotes().iterator().next();
+    if (selectedMote.getInterfaces().getRadio() == null) {
+      return;
+    }
+    
     final Position sPos = selectedMote.getInterfaces().getPosition();
 
     /* Paint transmission and interference range for selected mote */

tools/cooja/java/org/contikios/cooja/plugins/Visualizer.java

@@ -30,10 +30,12 @@
 
 package org.contikios.cooja.plugins;
 
+import java.awt.BasicStroke;
 import java.awt.BorderLayout;
 import java.awt.Color;
 import java.awt.Cursor;
 import java.awt.Dimension;
+import java.awt.Event;
 import java.awt.Graphics;
 import java.awt.Graphics2D;
 import java.awt.Point;
@@ -55,7 +57,7 @@ import java.awt.event.ItemListener;
 import java.awt.event.KeyEvent;
 import java.awt.event.MouseAdapter;
 import java.awt.event.MouseEvent;
-import java.awt.event.MouseMotionListener;
+import java.awt.event.MouseMotionAdapter;
 import java.awt.event.MouseWheelEvent;
 import java.awt.event.MouseWheelListener;
 import java.awt.geom.AffineTransform;
@@ -64,9 +66,14 @@ import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.LinkedList;
 import java.util.List;
+import java.util.Map;
 import java.util.Observable;
 import java.util.Observer;
+import java.util.Set;
 
 import javax.swing.AbstractAction;
 import javax.swing.Action;
@@ -74,7 +81,6 @@ import javax.swing.JCheckBoxMenuItem;
 import javax.swing.JMenu;
 import javax.swing.JMenuBar;
 import javax.swing.JMenuItem;
-import javax.swing.JOptionPane;
 import javax.swing.JPanel;
 import javax.swing.JPopupMenu;
 import javax.swing.JSeparator;
@@ -128,6 +134,7 @@ import org.contikios.cooja.plugins.skins.UDGMVisualizerSkin;
  * @see #registerVisualizerSkin(Class)
  * @see UDGMVisualizerSkin
  * @author Fredrik Osterlind
+ * @author Enrico Jorns
  */
 @ClassDescription("Network")
 @PluginType(PluginType.SIM_STANDARD_PLUGIN)
@@ -149,20 +156,34 @@ public class Visualizer extends VisPlugin implements HasQuickHelp {
   private AffineTransform viewportTransform;
   public int resetViewport = 0;
 
-  /* Actions: move motes, pan view, and zoom view */
+  private static final int SELECT_MASK = Event.CTRL_MASK;
-  private boolean panning = false;
+  private static final int MOVE_MASK = Event.SHIFT_MASK;
-  private Position panningPosition = null; /* Panning start position */
+
-  private boolean zooming = false;
+  enum MotesActionState {
-  private double zoomStart = 0;
+
-  private Position zoomingPosition = null; /* Zooming center position */
+    UNKNWON,
-  private Point zoomingPixel = null; /* Zooming center pixel */
+    SELECT_PRESS,
-  private boolean moving = false;
+    DEFAULT_PRESS,
-  private Point mouseDownPixel = null; /* Records position of mouse down to differentiate a click from a move */
+    PAN_PRESS,
-  private Mote movedMote = null;
+    PANNING,
-  public Mote clickedMote = null;
+    MOVING,
+    // rectangular select
+    SELECTING
+  }
+
+  /* All selected motes */
+  public Set<Mote> selectedMotes = new HashSet<>();
+  /* Mote that was under curser while mouse press */
+  Mote cursorMote;
+
+  MotesActionState mouseActionState = MotesActionState.UNKNWON;
+  /* Position where mouse button was pressed */
+  Position pressedPos;
+
+  private Set<Mote> movedMotes = null;
   private long moveStartTime = -1;
-  private boolean moveConfirm;
+  private static final Cursor MOVE_CURSOR = new Cursor(Cursor.MOVE_CURSOR);
-  private Cursor moveCursor = new Cursor(Cursor.MOVE_CURSOR);
+  private Selection selection;
 
   /* Visualizers */
   private static ArrayList<Class<? extends VisualizerSkin>> visualizerSkins =
@@ -277,6 +298,7 @@ public class Visualizer extends VisPlugin implements HasQuickHelp {
     });
     zoomMenu.add(resetViewportItem);
 
+    selection = new Selection();
     /* Main canvas */
     canvas = new JPanel() {
       private static final long serialVersionUID = 1L;
@@ -296,6 +318,7 @@ public class Visualizer extends VisPlugin implements HasQuickHelp {
         for (VisualizerSkin skin: currentSkins) {
           skin.paintAfterMotes(g);
         }
+        selection.drawSelection(g);
       }
     };
     canvas.setBackground(Color.WHITE);
@@ -378,18 +401,16 @@ public class Visualizer extends VisPlugin implements HasQuickHelp {
     });
 
     /* Popup menu */
-    canvas.addMouseMotionListener(new MouseMotionListener() {
+    canvas.addMouseMotionListener(new MouseMotionAdapter() {
-      public void mouseMoved(MouseEvent e) {
+      @Override
-        handleMouseMove(e, false);
-      }
       public void mouseDragged(MouseEvent e) {
-        handleMouseMove(e, false);
+        handleMouseDrag(e, false);
       }
     });
     canvas.addMouseListener(new MouseAdapter() {
       public void mousePressed(MouseEvent e) {
         if (e.isPopupTrigger()) {
-          handlePopupRequest(e.getPoint().x, e.getPoint().y);
+          handlePopupRequest(e.getPoint());
           return;
         }
 
@@ -399,19 +420,13 @@ public class Visualizer extends VisPlugin implements HasQuickHelp {
       }
       public void mouseReleased(MouseEvent e) {
         if (e.isPopupTrigger()) {
-          handlePopupRequest(e.getPoint().x, e.getPoint().y);
+          handlePopupRequest(e.getPoint());
           return;
         }
 
-        handleMouseMove(e, true);
+        if (SwingUtilities.isLeftMouseButton(e)) {
-      }
+          handleMouseRelease(e);
-      public void mouseClicked(MouseEvent e) {
-        if (e.isPopupTrigger()) {
-          handlePopupRequest(e.getPoint().x, e.getPoint().y);
         }
-
-        handleMouseMove(e, true);
-        repaint();
       }
     });
     canvas.addMouseWheelListener(new MouseWheelListener() {
@@ -645,11 +660,11 @@ public class Visualizer extends VisPlugin implements HasQuickHelp {
     visualizerSkins.remove(skin);
   }
 
-  private void handlePopupRequest(final int x, final int y) {
+  private void handlePopupRequest(Point point) {
     JPopupMenu menu = new JPopupMenu();
 
     /* Mote specific actions */
-    final Mote[] motes = findMotesAtPosition(x, y);
+    final Mote[] motes = findMotesAtPosition(point.x, point.y);
     if (motes != null && motes.length > 0) {
       menu.add(new JSeparator());
 
@@ -679,7 +694,7 @@ public class Visualizer extends VisPlugin implements HasQuickHelp {
 
     /* Simulation specific actions */
     menu.add(new JSeparator());
-    for (Class<? extends SimulationMenuAction> menuActionClass: simulationMenuActions) {
+    for (Class<? extends SimulationMenuAction> menuActionClass : simulationMenuActions) {
       try {
         final SimulationMenuAction menuAction = menuActionClass.newInstance();
         if (menuAction.isEnabled(this, simulation)) {
@@ -709,8 +724,8 @@ public class Visualizer extends VisPlugin implements HasQuickHelp {
 
     /* Show menu */
     menu.setLocation(new Point(
-        canvas.getLocationOnScreen().x + x,
+            canvas.getLocationOnScreen().x + point.x,
-        canvas.getLocationOnScreen().y + y));
+            canvas.getLocationOnScreen().y + point.y));
     menu.setInvoker(canvas);
     menu.setVisible(true);
   }
@@ -826,43 +841,169 @@ public class Visualizer extends VisPlugin implements HasQuickHelp {
   private void handleMousePress(MouseEvent mouseEvent) {
     int x = mouseEvent.getX();
     int y = mouseEvent.getY();
-    clickedMote = null;
 
-    if (mouseEvent.isControlDown()) {
+    pressedPos = transformPixelToPosition(mouseEvent.getPoint());
-      /* Zoom */
+
-      zooming = true;
+    // this is the state we have from pressing button
-      zoomingPixel = new Point(x, y);
+    final Mote[] foundMotes = findMotesAtPosition(x, y);
-      zoomingPosition = transformPixelToPosition(zoomingPixel);
+    if (foundMotes == null) {
-      zoomStart = viewportTransform.getScaleX();
+      cursorMote = null;
-      return;
+    }
+    else {
+      // select top mote
+      cursorMote = foundMotes[foundMotes.length - 1];
     }
 
-    final Mote[] motes = findMotesAtPosition(x, y);
+    int modifiers = mouseEvent.getModifiers();
-    if (mouseEvent.isShiftDown() ||
-        (!mouseEvent.isAltDown() && (motes == null || motes.length == 0))) {
-      /* No motes clicked or shift pressed: We should pan */
-      panning = true;
-      panningPosition = transformPixelToPosition(x, y);
-      return;
-    }
 
-    if (motes != null && motes.length > 0) {
+    /* translate input */
-      /* One of the clicked motes should be moved */
+    if ((modifiers & SELECT_MASK) != 0) {
-      mouseDownPixel = new Point(x, y);
+      mouseActionState = MotesActionState.SELECT_PRESS;
-      clickedMote = motes[0];
+    }
-      beginMoveRequest(motes[0], false, false);
+    else if ((modifiers & MOVE_MASK) != 0) {
+      // only move viewport
+      mouseActionState = MotesActionState.PAN_PRESS;
+    }
+    else {
+      if (foundMotes == null) {
+        // move viewport
+        selectedMotes.clear();
+      }
+      else {
+        // if this mote was not selected before, assume a new selection
+        if (!selectedMotes.contains(cursorMote)) {
+          selectedMotes.clear();
+          selectedMotes.add(cursorMote);
+        }
+      }
+      mouseActionState = MotesActionState.DEFAULT_PRESS;
+    }
+    repaint();
+  }
+
+  Map<Mote, double[]> moveStartPositions = new HashMap<>();
+
+  private void handleMouseDrag(MouseEvent e, boolean stop) {
+    Position currPos = transformPixelToPosition(e.getPoint());
+
+    switch (mouseActionState) {
+      case DEFAULT_PRESS:
+        if (cursorMote == null) {
+          mouseActionState = MotesActionState.PANNING;
+        }
+        else {
+          mouseActionState = MotesActionState.MOVING;
+          // save start position
+          for (Mote m : selectedMotes) {
+            Position pos = m.getInterfaces().getPosition();
+            moveStartPositions.put(m, new double[]{
+              pos.getXCoordinate(),
+              pos.getYCoordinate(),
+              pos.getZCoordinate()});
+          }
+        }
+        break;
+      case MOVING:
+        canvas.setCursor(MOVE_CURSOR);
+        for (Mote moveMote : selectedMotes) {
+          moveMote.getInterfaces().getPosition().setCoordinates(
+                  moveStartPositions.get(moveMote)[0]
+                  + (currPos.getXCoordinate() - pressedPos.getXCoordinate()),
+                  moveStartPositions.get(moveMote)[1]
+                  + (currPos.getYCoordinate() - pressedPos.getYCoordinate()),
+                  moveStartPositions.get(moveMote)[2]
+          );
+          repaint();
+        }
+        break;
+      case PAN_PRESS:
+        mouseActionState = MotesActionState.PANNING;
+        break;
+      case PANNING:
+        /* The current mouse position should correspond to where panning started */
+        viewportTransform.translate(
+                currPos.getXCoordinate() - pressedPos.getXCoordinate(),
+                currPos.getYCoordinate() - pressedPos.getYCoordinate()
+        );
+        repaint();
+        break;
+      case SELECT_PRESS:
+        mouseActionState = MotesActionState.SELECTING;
+        selection.setEnabled(true);
+        break;
+      case SELECTING:
+        int pressedX = transformToPixelX(pressedPos.getXCoordinate());
+        int pressedY = transformToPixelY(pressedPos.getYCoordinate());
+        int currX = transformToPixelX(currPos.getXCoordinate());
+        int currY = transformToPixelY(currPos.getYCoordinate());
+        int startX = pressedX < currX ? pressedX : currX;
+        int startY = pressedY < currY ? pressedY : currY;
+        int width = Math.abs(pressedX - currX);
+        int height = Math.abs(pressedY - currY);
+
+        selection.setSelection(startX, startY, width, height);
+        selectedMotes.clear();
+        selectedMotes.addAll(Arrays.asList(findMotesInRange(startX, startY, width, height)));
+
+        repaint();
+        break;
     }
   }
 
-  private void beginMoveRequest(Mote moteToMove, boolean withTiming, boolean confirm) {
+  private void handleMouseRelease(MouseEvent mouseEvent) {
+
+    switch (mouseActionState) {
+      case PAN_PRESS:
+        // ignore
+        break;
+      case SELECT_PRESS:
+        if (cursorMote == null) {
+          /* Click on free canvas deselects all mote */
+          selectedMotes.clear();
+        }
+        else {
+          /* toggle selection for mote */
+          if (selectedMotes.contains(cursorMote)) {
+            selectedMotes.remove(cursorMote);
+          }
+          else {
+            selectedMotes.add(cursorMote);
+          }
+        }
+        break;
+      case DEFAULT_PRESS:
+        if (cursorMote == null) {
+          /* Click on free canvas deselects all mote */
+          selectedMotes.clear();
+        }
+        else {
+          /* Click on mote selects single mote */
+          selectedMotes.clear();
+          selectedMotes.add(cursorMote);
+        }
+        break;
+      case MOVING:
+        /* Release stops moving */
+        canvas.setCursor(Cursor.getDefaultCursor());
+        break;
+      case SELECTING:
+        /* Release stops moving */
+        selection.setEnabled(false);
+        repaint();
+        break;
+    }
+    repaint();
+  }
+
+  private void beginMoveRequest(Mote motesToMove, boolean withTiming, boolean confirm) {
     if (withTiming) {
       moveStartTime = System.currentTimeMillis();
     } else {
       moveStartTime = -1;
     }
-    moving = true;
+    mouseActionState = MotesActionState.DEFAULT_PRESS;
-    moveConfirm = confirm;
+    selectedMotes.clear();
-    movedMote = moteToMove;
+    selectedMotes.add(motesToMove);
     repaint();
   }
 
@@ -888,107 +1029,37 @@ public class Visualizer extends VisPlugin implements HasQuickHelp {
     repaint();
   }
 
-  private void handleMouseMove(MouseEvent e, boolean stop) {
+  /**
-    int x = e.getX();
+   * Returns all motes in rectangular range
-    int y = e.getY();
+   *
-
+   * @param startX
-    /* Panning */
+   * @param startY
-    if (panning) {
+   * @param width
-      if (panningPosition == null || stop) {
+   * @param height
-        panning = false;
+   * @return All motes in range
-        return;
+   */
+  public Mote[] findMotesInRange(int startX, int startY, int width, int height) {
+    List<Mote> motes = new LinkedList<>();
+    for (Mote m : simulation.getMotes()) {
+      Position pos = m.getInterfaces().getPosition();
+      int moteX = transformToPixelX(pos.getXCoordinate());
+      int moteY = transformToPixelY(pos.getYCoordinate());
+      if (moteX > startX && moteX < startX + width
+              && moteY > startY && moteY < startY + height) {
+        motes.add(m);
       }
-
-      /* The current mouse position should correspond to where panning started */
-      Position moved = transformPixelToPosition(x,y);
-      viewportTransform.translate(
-          moved.getXCoordinate() - panningPosition.getXCoordinate(),
-          moved.getYCoordinate() - panningPosition.getYCoordinate()
-      );
-      repaint();
-      return;
-    }
-
-    /* Zooming */
-    if (zooming) {
-      if (zoomingPosition == null || zoomingPixel == null || stop) {
-        zooming = false;
-        return;
-      }
-
-      /* The zooming start pixel should correspond to the zooming center position */
-      /* The current mouse position should correspond to where panning started */
-      double zoomFactor = 1.0 + Math.abs((double) zoomingPixel.y - y)/100.0;
-      double newZoom = (zoomingPixel.y - y)>0?zoomStart*zoomFactor: zoomStart/zoomFactor;
-      if (newZoom < 0.00001) {
-        newZoom = 0.00001;
-      }
-      viewportTransform.setToScale(
-          newZoom,
-          newZoom
-      );
-      Position moved = transformPixelToPosition(zoomingPixel);
-      viewportTransform.translate(
-          moved.getXCoordinate() - zoomingPosition.getXCoordinate(),
-          moved.getYCoordinate() - zoomingPosition.getYCoordinate()
-      );
-      repaint();
-      return;
-    }
-
-    /* Moving */
-    if (moving) {
-      if(x != mouseDownPixel.x || y != mouseDownPixel.y) {
-        Position newPos = transformPixelToPosition(x, y);
-
-        if (!stop) {
-          canvas.setCursor(moveCursor);
-          movedMote.getInterfaces().getPosition().setCoordinates(
-              newPos.getXCoordinate(),
-              newPos.getYCoordinate(),
-              movedMote.getInterfaces().getPosition().getZCoordinate()
-          );
-          repaint();
-          return;
-        }
-        /* Restore cursor */
-        canvas.setCursor(Cursor.getDefaultCursor());
-
-
-        /* Move mote */
-        if (moveStartTime < 0 || System.currentTimeMillis() - moveStartTime > 300) {
-          if (moveConfirm) {
-            String options[] = {"Yes", "Cancel"};
-            int returnValue = JOptionPane.showOptionDialog(Visualizer.this,
-                "Move mote to" +
-                "\nX=" + newPos.getXCoordinate() +
-                "\nY=" + newPos.getYCoordinate() +
-                "\nZ=" + movedMote.getInterfaces().getPosition().getZCoordinate(),
-                "Move mote?",
-                JOptionPane.YES_NO_OPTION, JOptionPane.QUESTION_MESSAGE,
-                null, options, options[0]);
-            moving = returnValue == JOptionPane.YES_OPTION;
-          }
-          if (moving) {
-            movedMote.getInterfaces().getPosition().setCoordinates(
-                newPos.getXCoordinate(),
-                newPos.getYCoordinate(),
-                movedMote.getInterfaces().getPosition().getZCoordinate()
-            );
-            repaint();
-          }
-        }
-      }
-
-      moving = false;
-      movedMote = null;
-      repaint();
     }
+    Mote[] motesArr = new Mote[motes.size()];
+    return motes.toArray(motesArr);
   }
 
   /**
    * Returns all motes at given position.
    *
+   * If multiple motes were found on at a position the motes are returned
+   * in the order they are painted on screen.
+   * First mote in array is the bottom mote, last mote is the top mote.
+   *
    * @param clickedX
    *          X coordinate
    * @param clickedY
@@ -1066,7 +1137,7 @@ public class Visualizer extends VisPlugin implements HasQuickHelp {
       int x = pixelCoord.x;
       int y = pixelCoord.y;
 
-      if (mote == movedMote) {
+      if (mote == movedMotes) {
         g.setColor(MOVE_COLOR);
         g.fillOval(x - MOTE_RADIUS, y - MOTE_RADIUS, 2 * MOTE_RADIUS,
             2 * MOTE_RADIUS);
@@ -1292,8 +1363,8 @@ public class Visualizer extends VisPlugin implements HasQuickHelp {
   /**
    * @return Selected mote
    */
-  public Mote getSelectedMote() {
+  public Set<Mote> getSelectedMotes() {
-    return clickedMote;
+    return selectedMotes;
   }
 
   public Collection<Element> getConfigXML() {
@@ -1585,4 +1656,44 @@ public class Visualizer extends VisPlugin implements HasQuickHelp {
     "Multiple views can be active at the same time. " +
     "Use the View menu to select views. ";
   };
+
+  private class Selection {
+
+    private int x;
+    private int y;
+    private int width;
+    private int height;
+    private boolean enable;
+
+    public void setSelection(int x, int y, int width, int height) {
+      this.x = x;
+      this.y = y;
+      this.width = width;
+      this.height = height;
+    }
+
+    public void setEnabled(boolean enable) {
+      this.enable = enable;
+    }
+
+    public void drawSelection(Graphics g) {
+      /* only draw if enabled */
+      if (!enable) {
+        return;
+      }
+      Graphics2D g2d = (Graphics2D) g;
+      g2d.setColor(new Color(64, 64, 64, 10));
+      g2d.fillRect(x, y, width, height);
+
+      BasicStroke dashed
+              = new BasicStroke(1.0f,
+                                BasicStroke.CAP_BUTT,
+                                BasicStroke.JOIN_MITER,
+                                10.0f, new float[]{5.0f}, 0.0f);
+      g2d.setColor(Color.BLACK);
+      g2d.setStroke(dashed);
+      g2d.drawRect(x, y, width, height);
+    }
+  }
+
 }

tools/cooja/java/org/contikios/cooja/plugins/skins/DGRMVisualizerSkin.java

@@ -34,6 +34,7 @@ import java.awt.Color;
 import java.awt.FontMetrics;
 import java.awt.Graphics;
 import java.awt.Point;
+import java.util.Set;
 
 import org.apache.log4j.Logger;
 
@@ -74,21 +75,25 @@ public class DGRMVisualizerSkin implements VisualizerSkin {
 	}
 
 	public Color[] getColorOf(Mote mote) {
-	  Mote selectedMote = visualizer.getSelectedMote();
+	  if (visualizer.getSelectedMotes().contains(mote)) {
-	  if (mote == selectedMote) {
 	    return new Color[] { Color.CYAN };
 	  }
 	  return null;
 	}
 
 	public void paintBeforeMotes(Graphics g) {
-          Mote selectedMote = visualizer.getSelectedMote();
+		Set<Mote> selectedMotes = visualizer.getSelectedMotes();
 		if (simulation == null
-				|| selectedMote == null
+				|| selectedMotes == null
-				|| selectedMote.getInterfaces().getRadio() == null) {
+				|| selectedMotes.isEmpty()) {
 			return;
 		}
 
+		final Mote selectedMote = visualizer.getSelectedMotes().iterator().next();
+		if (selectedMote.getInterfaces().getRadio() == null) {
+		return;
+		}
+		
 		/* Paint transmission and interference range for selected mote */
 		Position motePos = selectedMote.getInterfaces().getPosition();
 

tools/cooja/java/org/contikios/cooja/plugins/skins/UDGMVisualizerSkin.java

@@ -36,6 +36,7 @@ import java.awt.FontMetrics;
 import java.awt.Graphics;
 import java.awt.Point;
 import java.beans.PropertyVetoException;
+import java.util.Set;
 
 import javax.swing.BorderFactory;
 import javax.swing.Box;
@@ -259,8 +260,7 @@ public class UDGMVisualizerSkin implements VisualizerSkin {
 
   @Override
   public Color[] getColorOf(Mote mote) {
-    Mote selectedMote = visualizer.getSelectedMote();
+    if (visualizer.getSelectedMotes().contains(mote)) {
-    if (mote == selectedMote) {
       return new Color[] { Color.CYAN };
     }
     return null;
@@ -268,10 +268,15 @@ public class UDGMVisualizerSkin implements VisualizerSkin {
 
   @Override
   public void paintBeforeMotes(Graphics g) {
-    Mote selectedMote = visualizer.getSelectedMote();
+    Set<Mote> selectedMotes = visualizer.getSelectedMotes();
     if (simulation == null
-        || selectedMote == null
+        || selectedMotes == null
-        || selectedMote.getInterfaces().getRadio() == null) {
+        || selectedMotes.isEmpty()) {
+      return;
+    }
+
+    final Mote selectedMote = visualizer.getSelectedMotes().iterator().next();
+    if (selectedMote.getInterfaces().getRadio() == null) {
       return;
     }