Make keyboard navigation in generic wxTreeCtrl more Mac-like under OS X.

In the native OS X tree control right cursor arrow expands the current item
and the left one collapses it if it's expanded, make the generic control work
like this too under Mac.

Closes #12019.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64227 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/treectlg.cpp

@@ -3076,6 +3076,21 @@ void wxGenericTreeCtrl::OnChar( wxKeyEvent &event )
     // end   : go to last item without opening parents
     // alnum : start or continue searching for the item with this prefix
     int keyCode = event.GetKeyCode();
+
+#ifdef __WXOSX__
+    // Make the keys work as they do in the native control:
+    // right => expand
+    // left => collapse if current item is expanded
+    if (keyCode == WXK_RIGHT)
+    {
+        keyCode = '+';
+    }
+    else if (keyCode == WXK_LEFT && IsExpanded(m_current))
+    {
+        keyCode = '-';
+    }
+#endif // __WXOSX__
+
     switch ( keyCode )
     {
         case '+':