Comment # 19 on bug 1074051 from Vinzenz Vietzke

I guess that would be something for upstream development. As I can see you
already opened a bug report there:
https://bugzilla.xfce.org/show_bug.cgi?id=14122
Maybe ask in #xfce-dev on Freenode IRC or via mailing lists if and how someone
could help you with this problem. 

I'll close this bug report for now but feel free to reopen it anytime.