Windows not visible into xfce4-panel using CTWM

Hello,

I have tested JWM, EVILWM and CTWM in combination with xfce4-panel.

xfce4-panel has the feature to add a button bar.
Into "Window Buttons", Switch bettern open windows using button.
It may be looking like a normal taskbar, like normal conventional pc (what
is actually a normal standard?).

So, JWM + XFCE4-PANEL with buttons, works flawlessly.
Evilwm + xfce4-panel with buttons works well too.

CTWM results no single windows shown into xfce4-panel. Maybe ctwm forgets
to tell X about the windows that are visible on the desktop?

Looking forward to hearing you.

I hope that this report help the development.