14.1.11 Setting and Reading the WM_COLORMAP_WINDOWS Property
Xlib provides functions that you can use to set and read
the WM_COLORMAP_WINDOWS property for a given window.
To set a window's WM_COLORMAP_WINDOWS property, use
XSetWMColormapWindows().
To read a window's WM_COLORMAP_WINDOWS property, use
XGetWMColormapWindows().
Christophe Tronche, ch@tronche.com