Function xcb::ffi::xproto::xcb_query_extension

pub unsafe extern "C" fn xcb_query_extension(
    c: *mut xcb_connection_t, 
    name_len: u16, 
    name: *const c_char
) -> xcb_query_extension_cookie_t

check if extension is present

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.