xcb_query_extension

Section: XCB Requests (3)
Updated: libxcb 1.12
Index Return to Main Contents

---

 

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.  

SEE ALSO

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

AUTHOR

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

---

 

Index

NAME

SYNOPSIS

Request function

Reply datastructure

Reply function

REQUEST ARGUMENTS

REPLY FIELDS

DESCRIPTION

RETURN VALUE

ERRORS

SEE ALSO

AUTHOR