xcb_query_extension

Section: XCB Requests (3)
Updated: libxcb 1.13.1
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NAME

xcb_query_extension - check if extension is present

SYNOPSIS

#include <xcb/xproto.h>

Request function

: xcb_query_extension_cookie_t xcb_query_extension(xcb_connection_t *conn, uint16_t name_len, const char *name);

Reply datastructure


typedef struct xcb_query_extension_reply_t {
    uint8_t  response_type;
    uint8_t  pad0;
    uint16_t sequence;
    uint32_t length;
    uint8_t  present;
    uint8_t  major_opcode;
    uint8_t  first_event;
    uint8_t  first_error;
} xcb_query_extension_reply_t;

Reply function

: xcb_query_extension_reply_t *xcb_query_extension_reply(xcb_connection_t *conn, xcb_query_extension_cookie_t cookie, xcb_generic_error_t **e);

REQUEST ARGUMENTS

conn: The XCB connection to X11.
name_len: The length of name in bytes.
name: The name of the extension to query, for example "RANDR". This is case sensitive!

REPLY FIELDS

response_type: The type of this reply, in this case XCB_QUERY_EXTENSION. This field is also present in the xcb_generic_reply_t and can be used to tell replies apart from each other.
sequence: The sequence number of the last request processed by the X11 server.
length: The length of the reply, in words (a word is 4 bytes).
present: Whether the extension is present on this X11 server.
major_opcode: The major opcode for requests.
first_event: The first event code, if any.
first_error: The first error code, if any.

DESCRIPTION

Determines if the specified extension is present on this X11 server.

Every extension has a unique major_opcode to identify requests, the minor opcodes and request formats are extension-specific. If the extension provides events and errors, the first_event and first_error fields in the reply are set accordingly.

There should rarely be a need to use this request directly, XCB provides the xcb_get_extension_data function instead.

RETURN VALUE

Returns an xcb_query_extension_cookie_t. Errors have to be handled when calling the reply function xcb_query_extension_reply.

If you want to handle errors in the event loop instead, use xcb_query_extension_unchecked. See xcb-requests(3) for details.

ERRORS

This request does never generate any errors.

AUTHOR

Generated from xproto.xml. Contact xcb@lists.freedesktop.org for corrections and improvements.