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xcb_query_extension
Section: XCB Requests (3)Updated: libxcb 1.12
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NAME
xcb_query_extension - check if extension is presentSYNOPSIS
#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.