fullscreen not quite using all the screen

I'm using XFCE with a "panel" (sort of "toolbar", the application's
name is "xfce4-panel") on the top border of the screen (24 pixels high).

This comes with an option (enabled by default) to "reserve space on
borders", which tells the window manager that the normal windows should
not overlap the panel (basically, in my case it means that when I "zoom
vertically" a window its top edge won't be at the top-edge of the
screen but only at the bottom edge of my panel).

For some reason, ctwm obeys this setting not only for normal windows but
also for fullscreen windows.  So if I start `evince` on a PDF file with
slides and then hit F5 to start the presentation, my 24-pixel-high
"panel" is still visible at the top.

That seems like a bug to me.  I currently work around it by changing the
panel's config, but is it something that can be configured in ctwm or
should it be fixed in the source code, or is it considered a feature
(e.g. mandated by the freedesktop rules)?


        Stefan