Fixed|libappfw: Menu closes open subwidgets when opening a new subwidget

Todo for later: If necessary, this could be a behavior flag in
MenuWidget.

IssueID #1730

doomsday/sdk/libappfw/include/de/widgets/menuwidget.h

@@ -27,6 +27,7 @@
 #include "../GridLayout"
 #include "../ScrollAreaWidget"
 #include "../ButtonWidget"
+#include "../PanelWidget"
 
 namespace de {
 
@@ -139,6 +140,14 @@ class LIBAPPFW_PUBLIC MenuWidget : public ScrollAreaWidget
 public slots:
     void dismissPopups();
 
+signals:
+    /**
+     * Called when a submenu/widget is opened by one of the items.
+     *
+     * @param panel  Panel that was opened.
+     */
+    void subWidgetOpened(de::PanelWidget *panel);
+
 private:
     DENG2_PRIVATE(d)
 };

doomsday/sdk/libappfw/src/widgets/menuwidget.cpp

@@ -329,6 +329,14 @@ DENG2_PIMPL(MenuWidget)
 
         w->audienceForClose() += this;
         w->audienceForDeletion() += this;
+
+        emit self.subWidgetOpened(w);
+
+        // Automatically close other subwidgets when one is opened.
+        foreach(auto *panel, openSubs)
+        {
+            if(panel != w) panel->close();
+        }
     }
 
     bool isVisibleItem(Widget const *child) const