Index: /trunk/src/VBox/Frontends/VirtualBox/src/globals/UIModalWindowManager.cpp
===================================================================
--- /trunk/src/VBox/Frontends/VirtualBox/src/globals/UIModalWindowManager.cpp	(revision 69002)
+++ /trunk/src/VBox/Frontends/VirtualBox/src/globals/UIModalWindowManager.cpp	(revision 69003)
@@ -228,4 +228,7 @@
         connect(pWindow, &QWidget::destroyed, this, &UIModalWindowManager::sltRemoveFromStack);
     }
+
+    /* Notify listeners that their stack may have changed: */
+    emit sigStackChanged();
 }
 
@@ -264,4 +267,7 @@
         }
     }
+
+    /* Notify listeners that their stack may have changed: */
+    emit sigStackChanged();
 }
 
Index: /trunk/src/VBox/Frontends/VirtualBox/src/globals/UIModalWindowManager.h
===================================================================
--- /trunk/src/VBox/Frontends/VirtualBox/src/globals/UIModalWindowManager.h	(revision 69002)
+++ /trunk/src/VBox/Frontends/VirtualBox/src/globals/UIModalWindowManager.h	(revision 69003)
@@ -30,4 +30,9 @@
 {
     Q_OBJECT;
+
+signals:
+
+    /** Notifies about stack changed. */
+    void sigStackChanged();
 
 public: