diff bed7f3f1a31946d417822613d01094ace514c73f uncommitted
--- a//sys/src/cmd/ktrans/main.c
+++ b//sys/src/cmd/ktrans/main.c
@@ -497,7 +497,7 @@
 
 	threadsetname("keytrans");
 	while(recv(input, &m) != -1){
-		if(m.code == 'r'){
+		if(m.code == 'z'){
 			emitutf(dictch, "", 1);
 			resetstr(&line, nil);
 			continue;
@@ -609,7 +609,7 @@
 			p++;
 			switch(msg.code){
 			case 'c': case 'k': case 'K':
-			case 'r':
+			case 'z':
 				break;
 			default:
 				goto Drop;
@@ -684,6 +684,8 @@
 	default:
 		usage();
 	}
+	if(write(kbdout, "z", 2) < 2)
+		sysfatal("failed to enable focus watch: %r");
 
 	memset(backspace, '\b', sizeof backspace-1);
 	backspace[sizeof backspace-1] = '\0';
--- a//sys/src/cmd/rio/dat.h
+++ b//sys/src/cmd/rio/dat.h
@@ -318,11 +318,14 @@
 enum{
 	Tapon = 'b',
 	Tapoff = 'e',
+	Tapwatch = 'z',
 };
-Channel *ctltap;	/* on/off messages */
+Channel *ctltap;	/* open/close */
+Channel *resptap;	/* open/close err */
 Channel	*fromtap;	/* input from kbd tap program to window */
 Channel *totap;		/* our keyboard input to tap program */
 Channel *wintap;	/* tell the tapthread which Window to send to */
+
 Window	*input;
 QLock	all;			/* BUG */
 Filsys	*filsys;
--- a//sys/src/cmd/rio/rio.c
+++ b//sys/src/cmd/rio/rio.c
@@ -199,7 +199,8 @@
 	totap = chancreate(sizeof(char*), 32);
 	fromtap = chancreate(sizeof(char*), 32);
 	wintap = chancreate(sizeof(Window*), 0);
-	ctltap = chancreate(sizeof(Window*), 0);
+	ctltap = chancreate(sizeof(char*), 0);
+	resptap = chancreate(sizeof(char*), 0);
 	proccreate(keyboardtap, nil, STACK);
 
 	wscreen = allocscreen(screen, background, 0);
@@ -350,17 +351,53 @@
 			write(window[i]->notefd, "hangup", 6); 
 }
 
+static int tapseats[] = { [OREAD] Tapoff, [OWRITE] Tapoff };
+
+char*
+tapctlmsg(char *msg)
+{
+	int perm;
+
+	perm = msg[1];
+	switch(msg[0]){
+	case Tapwatch:
+		if(tapseats[OREAD] == Tapoff)
+			return "no active reader";
+		tapseats[OREAD] = Tapwatch;
+		break;
+	case Tapoff:
+		if(perm == ORDWR)
+			tapseats[OREAD] = Tapoff, tapseats[OWRITE] = Tapoff;
+		else
+			tapseats[perm] = Tapoff;
+		break;
+	case Tapon:
+		switch(perm){
+		case ORDWR:
+			if(tapseats[OREAD] != Tapoff || tapseats[OWRITE] != Tapoff)
+				return "seat taken";
+			tapseats[OREAD] = Tapon, tapseats[OWRITE] = Tapon;
+			break;
+		case OREAD: case OWRITE:
+			if(tapseats[perm] != Tapoff)
+				return "seat taken";
+			tapseats[perm] = Tapon;
+			break;
+		}
+		break;
+	}
+	return nil;
+}
+
 void
 keyboardtap(void*)
 {
 	char *s, *ctl;
+	char *watched;
 	Window *w, *cur;
-	int mode;
-	enum { Awin, Actl, Afrom, Adev, Ato, Ainp, NALT };
-	enum { Mnorm, Mtap };
 
-	threadsetname("keyboardtap");	
-
+	threadsetname("keyboardtap");
+	enum { Awin, Actl, Afrom, Adev, Ato, Ainp, Awatch, NALT };
 	static Alt alts[NALT+1];
 	/* ctl */
 	alts[Awin].c = wintap;
@@ -383,10 +420,13 @@
 	alts[Ainp].c = nil;
 	alts[Ainp].v = &s;
 	alts[Ainp].op = CHANNOP;
+	alts[Awatch].c = totap;
+	alts[Awatch].v = &watched;
+	alts[Awatch].op = CHANNOP;
 	alts[NALT].op = CHANEND;
 
 	cur = nil;
-	mode = Mnorm;
+	watched = nil;
 	for(;;)
 		switch(alt(alts)){
 		case Awin:
@@ -393,20 +433,18 @@
 			cur = w;
 			if(cur != nil){
 				alts[Ainp].c = cur->ck;
-				break;
+				if(tapseats[OREAD] != Tapwatch)	
+					break;
+				if(alts[Awatch].op == CHANSND)
+					free(watched);
+				watched = smprint("z%d", cur->id);
+				alts[Awatch].op = CHANSND;
 			}
 			if(alts[Ainp].op != CHANNOP || alts[Ato].op != CHANNOP)
 				free(s);
 			goto Reset;
 		case Actl:
-			switch(*ctl){
-			case Tapon:
-				mode = Mtap;
-				break;
-			case Tapoff:
-				mode = Mnorm;
-				break;
-			}
+			sendp(resptap, tapctlmsg(ctl));
 			free(ctl);
 			break;
 		case Afrom:
@@ -420,16 +458,19 @@
 			alts[Ainp].op = CHANSND;
 			break;
 		case Adev:
-			if(mode == Mnorm && cur == nil){
+			if(tapseats[OWRITE] == Tapoff && cur == nil){
 				free(s);
 				break;
 			}
 			alts[Afrom].op = CHANNOP;
 			alts[Adev].op = CHANNOP;
-			if(mode == Mnorm)
+			if(tapseats[OWRITE] == Tapoff)
 				alts[Ainp].op = CHANSND;
 			else
 				alts[Ato].op = CHANSND;
+			break;
+		case Awatch:
+			alts[Awatch].op = CHANNOP;
 			break;
 		case Ainp:
 			if(*s == 'k' || *s == 'K')
--- a//sys/src/cmd/rio/xfid.c
+++ b//sys/src/cmd/rio/xfid.c
@@ -247,6 +247,7 @@
 {
 	Fcall t;
 	Window *w;
+	char *s;
 
 	w = x->f->w;
 	if(w != nil && w->deleted){
@@ -312,8 +313,12 @@
 		}
 		break;
 	case Qtap:
-		chanprint(ctltap, "%c", Tapon);
-		break;
+		chanprint(ctltap, "%c%c", Tapon, x->mode);
+		s = recvp(resptap);
+		if(s == nil)
+			break;
+		filsysrespond(x->fs, x, &t, s);
+		return;
 	}
 	t.qid = x->f->qid;
 	t.iounit = messagesize-IOHDRSZ;
@@ -369,7 +374,8 @@
 			w->wctlopen = FALSE;
 		break;
 	case Qtap:
-		chanprint(ctltap, "%c", Tapoff);
+		chanprint(ctltap, "%c%c", Tapoff, x->f->mode);
+		recvp(resptap);
 		break;
 	}
 	if(w)
@@ -382,7 +388,7 @@
 {
 	Fcall fc;
 	int cnt, qid, nb, nr;
-	char err[ERRMAX], *p, *e;
+	char err[ERRMAX], *p, *e, *s;
 	Point pt;
 	Window *w;
 	Rune *r;
@@ -581,12 +587,22 @@
 		}
 		e = x->data + cnt;
 		for(p = x->data; p < e; p += strlen(p)+1){
-			if(*p == '\0'){
+			switch(*p){
+			case '\0':
 				fc.count = p - x->data;
 				filsysrespond(x->fs, x, &fc, "null message type");
 				return;
+			case Tapwatch:
+				chanprint(ctltap, "%s", p);
+				s = recvp(resptap);
+				if(s == nil)
+					break;
+				filsysrespond(x->fs, x, &fc, s);
+				return;
+			default:
+				chanprint(fromtap, "%s", p);
+				break;	
 			}
-			chanprint(fromtap, "%s", p);
 		}
 		break;