--- libev/ev.3	2020/01/22 02:00:13	1.119
+++ libev/ev.3	2020/01/22 13:33:44	1.120
@@ -1351,8 +1351,9 @@
 corresponding stop function (\f(CW\*(C`ev_TYPE_stop (loop, watcher *)\*(C'\fR.
 .PP
 As long as your watcher is active (has been started but not stopped) you
-must not touch the values stored in it. Most specifically you must never
-reinitialise it or call its \f(CW\*(C`ev_TYPE_set\*(C'\fR macro.
+must not touch the values stored in it except when explicitly documented
+otherwise. Most specifically you must never reinitialise it or call its
+\&\f(CW\*(C`ev_TYPE_set\*(C'\fR macro.
 .PP
 Each and every callback receives the event loop pointer as first, the
 registered watcher structure as second, and a bitset of received events as
@@ -1955,8 +1956,14 @@
 .IX Item "ev_io_set (ev_io *, int fd, int events)"
 .PD
 Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
-receive events for and \f(CW\*(C`events\*(C'\fR is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or
-\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR, to express the desire to receive the given events.
+receive events for and \f(CW\*(C`events\*(C'\fR is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR, both
+\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR or \f(CW0\fR, to express the desire to receive the given
+events.
+.Sp
+Note that setting the \f(CW\*(C`events\*(C'\fR to \f(CW0\fR and starting the watcher is
+supported, but not specially optimized \- if your program sometimes happens
+to generate this combination this is fine, but if it is easy to avoid
+starting an io watcher watching for no events you should do so.
 .IP "ev_io_modify (ev_io *, int events)" 4
 .IX Item "ev_io_modify (ev_io *, int events)"
 Similar to \f(CW\*(C`ev_io_set\*(C'\fR, but only changes the event mask. Using this might
@@ -1970,9 +1977,9 @@
 \&\f(CW\*(C`ev_io_set\*(C'\fR for that.
 .IP "int events [no\-modify]" 4
 .IX Item "int events [no-modify]"
-The set of events being watched, among other flags. This field is a
-bit set \- to test for \f(CW\*(C`EV_READ\*(C'\fR, use \f(CW\*(C`w\->events & EV_READ\*(C'\fR, and
-similarly for \f(CW\*(C`EV_WRITE\*(C'\fR.
+The set of events the fd is being watched for, among other flags. Remember
+that this is a bit set \- to test for \f(CW\*(C`EV_READ\*(C'\fR, use \f(CW\*(C`w\->events &
+EV_READ\*(C'\fR, and similarly for \f(CW\*(C`EV_WRITE\*(C'\fR.
 .Sp
 As with \f(CW\*(C`fd\*(C'\fR, you must not modify this member even when the watcher is
 stopped, always use \f(CW\*(C`ev_io_set\*(C'\fR or \f(CW\*(C`ev_io_modify\*(C'\fR for that.
@@ -4413,6 +4420,9 @@
 .Sp
 For \f(CW\*(C`ev::embed\*(C'\fR watchers this method is called \f(CW\*(C`set_embed\*(C'\fR, to avoid
 clashing with the \f(CW\*(C`set (loop)\*(C'\fR method.
+.Sp
+For \f(CW\*(C`ev::io\*(C'\fR watchers there is an additional \f(CW\*(C`set\*(C'\fR method that acepts a
+new event mask only, and internally calls \f(CW\*(C`ev_io_modfify\*(C'\fR.
 .IP "w\->start ()" 4
 .IX Item "w->start ()"
 Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the