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XQueryExtension()					     XQueryExtension()

Name
  XQueryExtension – get extension information.

Synopsis
  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  a  connection  to  an  X	 server;  returned   from
	    XOpenDisplay().

  name	    Specifies  the  name  of the desired extension.  Uppercase or
	    lowercase is important.  If the extension name is not in  the
	    Host  Portable  Character Encoding, the result is implementa‐
	    tion-dependent.

  major_opcode_return
	    Returns the major opcode of the extension, for use	in  error
	    handling routines.

  first_event_return
	    Returns  the  code	of the first custom event type created by
	    the extension.

  first_error_return
	    Returns the code of the first custom  error	 defined  by  the
	    extension.

Returns
  True if the extension is present, else False.

Description
  XQueryExtension()  determines	 if  the  named extension is present, and
  returns True if it is.  If so, the routines in  the  extension  can  be
  used	just  as  if  they  were core Xlib requests, except that they may
  return new types of events or new error codes.   The	available  exten‐
  sions can be listed with XListExtensions().

  The  major_opcode_return  for the extension is returned, if it has one.
  Otherwise, zero is returned.	This opcode will appear in errors  gener‐
  ated in the extension.

  If  the  extension involves additional event types, the base event type
  code is returned in first_event_return.  Otherwise, zero is returned in
  first_event_return.  The format of the events is specific to the exten‐
  sion.

  If the extension involves additional error codes, the base  error  code
  is  returned	in first_error_return.	Otherwise, zero is returned.  The
  format of additional data in the errors is specific to the extension.

  See Volume One, Chapter 15,  Other  Programming  Techniques,	for  more
  information  on  using  extensions, and Volume One, Appendix C, Writing
  Extensions to X, for information on writing them.

See Also
  XFreeExtensionList(),	 XListExtensions().

Xlib - Extensions					     XQueryExtension()

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