sync edit menu checkbox state with the selected shape

src/main/java/ovh/gasser/newshapes/Selection.java

@@ -1,15 +1,22 @@
 package ovh.gasser.newshapes;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import ovh.gasser.newshapes.attributes.SelectionAttributes;
 import ovh.gasser.newshapes.shapes.Shape;
+import ovh.gasser.newshapes.ui.listeners.SelectionListener;
 import ovh.gasser.newshapes.util.Streamable;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 
 public class Selection implements Streamable<Shape> {
+    private final static Logger logger = LoggerFactory.getLogger(Selection.class);
+
     private final List<Shape> selectedShapes = new ArrayList<>();
+    private final List<SelectionListener> listeners = new ArrayList<>();
 
     @Override
     public Iterator<Shape> iterator() {
@@ -20,12 +27,26 @@ public class Selection implements Streamable<Shape> {
         for (Shape shape : selectedShapes) {
             shape.addAttributes(new SelectionAttributes(false));
         }
-
         selectedShapes.clear();
+        notifyListeners();
     }
 
     public void add(Shape s) {
+        logger.info("Selection.add");
         selectedShapes.add(s);
         s.addAttributes(new SelectionAttributes(true));
+        notifyListeners();
+    }
+
+    public List<Shape> getSelectedShapes() {
+        return List.copyOf(selectedShapes);
+    }
+
+    public void addListener(SelectionListener listener) {
+        this.listeners.add(listener);
+    }
+
+    private void notifyListeners(){
+        listeners.forEach(l -> l.onSelectionChanged(Collections.unmodifiableCollection(selectedShapes)));
     }
 }