#define MWM_HINTS_DECORATIONS (1L << 1)
#define PROP_MWM_HINTS_ELEMENTS 5

typedef struct {
  uint32_t  flags;
  uint32_t  functions;
  uint32_t  decorations;
  int32_t   input_mode;
  uint32_t  status;
} MWMHints;
...
		MWMHints mwmhints;
		Atom prop;
		memset(&mwmhints, 0, sizeof(mwmhints));
		prop = XInternAtom(Xdisplay, "_MOTIF_WM_HINTS", false);
		mwmhints.flags = MWM_HINTS_DECORATIONS;
		mwmhints.decorations = 0;
		XChangeProperty(Xdisplay, wnd.GetWindow(), prop, prop, 32, PropModeReplace,
		(unsigned char *) &mwmhints,
		PROP_MWM_HINTS_ELEMENTS);
...