XSetWMProtocols, XGetWMProtocols - set or read a window's WM_PROTOCOLS property
Status XSetWMProtocols(Display *display, Window
    w, Atom *protocols, int count);
Status XGetWMProtocols(Display *display, Window
    w, Atom **protocols_return, int *count_return);
  - display
- Specifies the connection to the X server.
- count
- Specifies the number of protocols in the list.
- count_return
- Returns the number of protocols in the list.
- protocols
- Specifies the list of protocols.
- protocols_return
- Returns the list of protocols.
The XSetWMProtocols function replaces the WM_PROTOCOLS property on the
  specified window with the list of atoms specified by the protocols argument.
  If the property does not already exist, XSetWMProtocols sets the
  WM_PROTOCOLS property on the specified window to the list of atoms specified
  by the protocols argument. The property is stored with a type of ATOM and a
  format of 32. If it cannot intern the WM_PROTOCOLS atom,
  XSetWMProtocols returns a zero status. Otherwise, it returns a nonzero
  status.XSetWMProtocols can generate BadAlloc and
    BadWindow errors.
The XGetWMProtocols function returns the list of atoms
    stored in the WM_PROTOCOLS property on the specified window. These atoms
    describe window manager protocols in which the owner of this window is
    willing to participate. If the property exists, is of type ATOM, is of
    format 32, and the atom WM_PROTOCOLS can be interned, XGetWMProtocols
    sets the protocols_return argument to a list of atoms, sets the count_return
    argument to the number of elements in the list, and returns a nonzero
    status. Otherwise, it sets neither of the return arguments and returns a
    zero status. To release the list of atoms, use XFree.
XGetWMProtocols can generate a BadWindow error.
  - WM_PROTOCOLS
- List of atoms that identify the communications protocols between the
      client and window manager in which the client is willing to
    participate.
  - BadAlloc
- The server failed to allocate the requested resource or server
    memory.
- BadWindow
- A value for a Window argument does not name a defined Window.
XAllocClassHint(3), XAllocIconSize(3), XAllocSizeHints(3), XAllocWMHints(3),
  XFree(3), XSetCommand(3), XSetTransientForHint(3), XSetTextProperty(3),
  XSetWMClientMachine(3), XSetWMColormapWindows(3), XSetWMIconName(3),
  XSetWMName(3), XSetWMProperties(3), XStringListToTextProperty(3)
Xlib - C Language X Interface