XQueryExtension()XQueryExtension()NameXQueryExtension – 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.
DescriptionXQueryExtension() 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 AlsoXFreeExtensionList(), XListExtensions().
Xlib - Extensions XQueryExtension()