allocate size for the extra controls in the file dialog (#9679)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@58270 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/fldlgcmn.cpp

@@ -168,6 +168,18 @@ bool wxFileDialogBase::CreateExtraControl()
     return true;
 }
 
+wxSize wxFileDialogBase::GetExtraControlSize()
+{
+    if ( !m_extraControlCreator )
+        return wxDefaultSize;
+
+    // create the extra control in an empty dialog just to find its size: this
+    // is not terribly efficient but we do need to know the size before
+    // creating the native dialog and this seems to be the only way
+    wxDialog dlg(NULL, wxID_ANY, "");
+    return (*m_extraControlCreator)(&dlg)->GetSize();
+}
+
 //----------------------------------------------------------------------------
 // wxFileDialog convenience functions
 //----------------------------------------------------------------------------