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xcb_query_extension(3) XCB Requests xcb_query_extension(3)


xcb_query_extension - check if extension is present


#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);


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


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.
The sequence number of the last request processed by the X11 server.
The length of the reply, in words (a word is 4 bytes).
Whether the extension is present on this X11 server.
The major opcode for requests.
The first event code, if any.
The first error code, if any.


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.


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.


This request does never generate any errors.


xcb-requests(3), xcb_get_extension_data(3), xdpyinfo(1)


Generated from xproto.xml. Contact for corrections and improvements.

libxcb 1.17.0 X Version 11