Add a callback for wakeups

tools/tui/loop/api.go

@@ -78,6 +78,9 @@ type Loop struct {
 
 	// Called when resuming from a SIGTSTP or Ctrl-z
 	OnResumeFromStop func() error
+
+	// Called when main loop is woken up
+	OnWakeup func() error
 }
 
 func New(options ...func(self *Loop)) (*Loop, error) {

tools/tui/loop/run.go

@@ -319,6 +319,12 @@ func (self *Loop) run() (err error) {
 			for len(self.wakeup_channel) > 0 {
 				<-self.wakeup_channel
 			}
+			if self.OnWakeup != nil {
+				err = self.OnWakeup()
+				if err != nil {
+					return err
+				}
+			}
 		case msg_id := <-write_done_channel:
 			self.flush_pending_writes(tty_write_channel)
 			if self.OnWriteComplete != nil {