.TH xcb_query_extension 3  "libxcb 1.14" "X Version 11" "XCB Requests"
.ad l
.SH NAME
xcb_query_extension \- check if extension is present
.SH SYNOPSIS
.hy 0
.B #include <xcb/xproto.h>
.SS Request function
.HP
xcb_query_extension_cookie_t \fBxcb_query_extension\fP(xcb_connection_t\ *\fIconn\fP, uint16_t\ \fIname_len\fP, const char\ *\fIname\fP);
.PP
.SS Reply datastructure
.nf
.sp
typedef struct xcb_query_extension_reply_t {
    uint8_t  \fIresponse_type\fP;
    uint8_t  \fIpad0\fP;
    uint16_t \fIsequence\fP;
    uint32_t \fIlength\fP;
    uint8_t  \fIpresent\fP;
    uint8_t  \fImajor_opcode\fP;
    uint8_t  \fIfirst_event\fP;
    uint8_t  \fIfirst_error\fP;
} \fBxcb_query_extension_reply_t\fP;
.fi
.SS Reply function
.HP
xcb_query_extension_reply_t *\fBxcb_query_extension_reply\fP(xcb_connection_t\ *\fIconn\fP, xcb_query_extension_cookie_t\ \fIcookie\fP, xcb_generic_error_t\ **\fIe\fP);
.br
.hy 1
.SH REQUEST ARGUMENTS
.IP \fIconn\fP 1i
The XCB connection to X11.
.IP \fIname_len\fP 1i
The length of \fIname\fP in bytes.
.IP \fIname\fP 1i
The name of the extension to query, for example "RANDR". This is case
sensitive!
.SH REPLY FIELDS
.IP \fIresponse_type\fP 1i
The type of this reply, in this case \fIXCB_QUERY_EXTENSION\fP. This field is also present in the \fIxcb_generic_reply_t\fP and can be used to tell replies apart from each other.
.IP \fIsequence\fP 1i
The sequence number of the last request processed by the X11 server.
.IP \fIlength\fP 1i
The length of the reply, in words (a word is 4 bytes).
.IP \fIpresent\fP 1i
Whether the extension is present on this X11 server.
.IP \fImajor_opcode\fP 1i
The major opcode for requests.
.IP \fIfirst_event\fP 1i
The first event code, if any.
.IP \fIfirst_error\fP 1i
The first error code, if any.
.SH DESCRIPTION
Determines if the specified extension is present on this X11 server.

Every extension has a unique \fImajor_opcode\fP to identify requests, the minor
opcodes and request formats are extension-specific. If the extension provides
events and errors, the \fIfirst_event\fP and \fIfirst_error\fP fields in the reply are
set accordingly.

There should rarely be a need to use this request directly, XCB provides the
\fIxcb_get_extension_data\fP function instead.
.SH RETURN VALUE
Returns an \fIxcb_query_extension_cookie_t\fP. Errors have to be handled when calling the reply function \fIxcb_query_extension_reply\fP.

If you want to handle errors in the event loop instead, use \fIxcb_query_extension_unchecked\fP. See \fBxcb-requests(3)\fP for details.
.SH ERRORS
This request does never generate any errors.
.SH SEE ALSO
.BR xcb-requests (3),
.BR xcb_get_extension_data (3),
.BR xdpyinfo (1)
.SH AUTHOR
Generated from xproto.xml. Contact xcb@lists.freedesktop.org for corrections and improvements.