also add wxSizer::IsEmpty()

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@57712 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/sizer.h

@@ -1093,6 +1093,9 @@ public:
 
     /**
        Returns the number of items in the sizer.
+
+       If you just need to test whether the sizer is empty or not you can also
+       use IsEmpty() function.
     */
     size_t GetItemCount() const;
 
@@ -1246,6 +1249,13 @@ public:
     */
     wxSizerItem* InsertStretchSpacer(size_t index, int prop = 1);
 
+    /**
+        Return @true if the sizer has no elements.
+
+        @see GetItemCount()
+     */
+    bool IsEmpty() const;
+
     /**
         Returns @true if the @a window is shown.