XQueryExtension(3X11)

     NAME
          XQueryExtension - determines availability of an extension

     SYNTAX
          Bool XQueryExtension(display, name, major_opcode_return,
          first_event_return, first_error_return)
                Display *display;
                char *name;
                int *major_opcode_return;
                int *first_event_return;
                int *first_error_return;

     ARGUMENTS
          display   Specifies the connection to the X server.

          name      Specifies the extension name.

          major_opcode_return
                    Returns the major opcode.

          first_event_return
                    Returns the first event code, if any.
                    Specifies the extension list.

     DESCRIPTION
          The XQueryExtension function determines if the named
          extension is present. If the extension is not present,
          XQueryExtension returns False; otherwise, it returns True.
          If the extension is present, XQueryExtension returns the
          major opcode for the extension to major_opcode_return;
          otherwise, it returns zero. Any minor opcode and the request
          formats are specific to the extension. If the extension
          involves additional event types, XQueryExtension returns the
          base event type code to first_event_return; otherwise, it
          returns zero. The format of the events is specific to the
          extension. If the extension involves additional error codes,
          XQueryExtension returns the base error code to
          first_error_return; otherwise, it returns zero. The format
          of additional data in the errors is specific to the
          extension.

     SEE ALSO
          XFreeExtensionList(), XListExtensions(), "Basic Protocol
          Support Routines".
          Xlib - C Language X Interface