Fix display of empty wxStaticBoxSizers.

wxStaticBoxSizer should be considered shown if its static box is shown, even
if it has no elements (or all of them are hidden).

Closes #14698.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73729 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/sizer.h

@@ -715,6 +715,10 @@ public:
 
     void Show(bool show) { ShowItems(show); }
 
+    // This is the ShowItems() counterpart and returns true if any of the sizer
+    // items are shown.
+    virtual bool AreAnyItemsShown() const;
+
 protected:
     wxSize              m_size;
     wxSize              m_minSize;
@@ -1033,6 +1037,7 @@ public:
 
     // override to hide/show the static box as well
     virtual void ShowItems (bool show);
+    virtual bool AreAnyItemsShown() const;
 
     virtual bool Detach( wxWindow *window );
     virtual bool Detach( wxSizer *sizer ) { return wxBoxSizer::Detach(sizer); }

src/common/sizer.cpp

@@ -602,20 +602,10 @@ bool wxSizerItem::IsShown() const
             return m_window->IsShown();
 
         case Item_Sizer:
-        {
             // arbitrarily decide that if at least one of our elements is
             // shown, so are we (this arbitrariness is the reason for
             // deprecating this function)
-            for ( wxSizerItemList::compatibility_iterator
-                    node = m_sizer->GetChildren().GetFirst();
-                  node;
-                  node = node->GetNext() )
-            {
-                if ( node->GetData()->IsShown() )
-                    return true;
-            }
-            return false;
-        }
+            return m_sizer->AreAnyItemsShown();
 
         case Item_Spacer:
             return m_spacer->IsShown();
@@ -1290,6 +1280,19 @@ void wxSizer::ShowItems( bool show )
     }
 }
 
+bool wxSizer::AreAnyItemsShown() const
+{
+    wxSizerItemList::compatibility_iterator node = m_children.GetFirst();
+    while (node)
+    {
+        if ( node->GetData()->IsShown() )
+            return true;
+        node = node->GetNext();
+    }
+
+    return false;
+}
+
 bool wxSizer::IsShown( wxWindow *window ) const
 {
     wxSizerItemList::compatibility_iterator node = m_children.GetFirst();
@@ -2541,6 +2544,16 @@ void wxStaticBoxSizer::ShowItems( bool show )
     wxBoxSizer::ShowItems( show );
 }
 
+bool wxStaticBoxSizer::AreAnyItemsShown() const
+{
+    // We don't need to check the status of our child items: if the box is
+    // shown, this sizer should be considered shown even if all its elements
+    // are hidden (or, more prosaically, there are no elements at all). And,
+    // conversely, if the box is hidden then all our items, which are its
+    // children, are hidden too.
+    return m_staticBox->IsShown();
+}
+
 bool wxStaticBoxSizer::Detach( wxWindow *window )
 {
     // avoid deleting m_staticBox in our dtor if it's being detached from the