xcb_take_socket: Document sequence wrap requirements

[free-sw/xcb/libxcb] / src / xcbext.h

diff --git a/src/xcbext.h b/src/xcbext.h
index 2e10ba2..d6366cb 100644 (file)
--- a/src/xcbext.h
+++ b/src/xcbext.h
@@ -65,15 +65,22 @@ unsigned int xcb_send_request(xcb_connection_t *c, int flags, struct iovec *vect
  * request XCB sent. The caller of xcb_take_socket must supply a
  * callback which XCB can call when it wants the write side of the
  * socket back to make a request. This callback synchronizes with the
- * external socket owner, flushes any output queues if appropriate, and
- * then returns the sequence number of the last request sent over the
- * socket. */
+ * external socket owner and flushes any output queues if appropriate.
+ * If you are sending requests which won't cause a reply, please note the
+ * comment for xcb_writev which explains some sequence number wrap issues.
+ * */
 int xcb_take_socket(xcb_connection_t *c, void (*return_socket)(void *closure), void *closure, int flags, uint64_t *sent);
 
 /* You must own the write-side of the socket (you've called
  * xcb_take_socket, and haven't returned from return_socket yet) to call
  * xcb_writev. Also, the iovec must have at least 1 byte of data in it.
- * */
+ * You have to make sure that xcb can detect sequence number wraps correctly.
+ * This means that the first request you send after xcb_take_socket must cause a
+ * reply (e.g. just insert a GetInputFocus request). After every (1 << 16) - 1
+ * requests without a reply, you have to insert a request which will cause a
+ * reply. You can again use GetInputFocus for this. You do not have to wait for
+ * any of the GetInputFocus replies, but can instead handle them via
+ * xcb_discard_reply(). */
 int xcb_writev(xcb_connection_t *c, struct iovec *vector, int count, uint64_t requests);