minor code cleaning

dockingvl/src/main/java/fr/soleil/docking/vl/view/VlDockView.java

@@ -32,7 +32,6 @@ import fr.soleil.docking.vl.SoleilDockingDesktop;
 public class VlDockView implements IView, Dockable, DockingActionListener, FocusListener {
     protected Object id;
     protected boolean enabled;
-    protected boolean visible;
     protected String title;
     protected Component component;
     protected Icon icon;
@@ -84,17 +83,17 @@ public class VlDockView implements IView, Dockable, DockingActionListener, Focus
     @Override
     public boolean isVisible() {
         DockableState state = dockingDesktop.getDockableState(this);
-        boolean tempVisible = false;
+        boolean visible = false;
         if (state != null) {
             Location location = state.getLocation();
-            tempVisible = (location != Location.CLOSED) && (location != Location.HIDDEN);
+            visible = (location != Location.CLOSED) && (location != Location.HIDDEN);
         }
-        return visible || tempVisible;
+        return visible;
     }
 
     @Override
     public void setVisible(boolean visible) {
-        this.visible = visible;
+        if (visible != isVisible()) {
             if (visible) {
                 dockingDesktop.showDockable(this);
             } else {
@@ -103,6 +102,7 @@ public class VlDockView implements IView, Dockable, DockingActionListener, Focus
             component.setVisible(visible);
             component.setEnabled(visible);
         }
+    }
 
     @Override
     public void select() {