XmIsMotifWMRunning — A function that determines whether the window manager is running

XmIsMotifWMRunning lets a user know whether the Motif Window Manager is running on a screen that contains
       a specific widget hierarchy.  This function first sees whether the _MOTIF_WM_INFO property is present  on
       the  root  window  of the shell's screen. If it is, its window field is used to query for the presence of
       the specified window as a child of root.

       shell     Specifies the shell whose screen will be tested for mwm's presence.

XmIsMotifWMRunning   —   A   function   that   determines   whether   the   window   manager  is  running
       "XmIsMotifWMRunning"

       Returns True if MWM is running.

                                                                                           XmIsMotifWMRunning(3)

       #include <Xm/Xm.h>
       BooleanXmIsMotifWMRunning(
       Widgetshell);