wine users - Mar 2007 - How does wine determine to draw non-client area according to managed mode setting?

Hello,

When wine runs on managed mode, it delegate drawing non-client
area(caption, frame-border) to window manager.
I found NC_DrawCaption function is not invoked on managed mode.
On non-managed mode, that function is invoked.

I tried to find routine which determine to draw non-client area
according to managed mode setting, but I can't.

please give me some hints about that.
Thank you.