20060303a

4 files changed, 1422 insertions, 0 deletions

diff --git a/appl/collab/clients/chat.b b/appl/collab/clients/chat.b
new file mode 100644
index 00000000..d9c78d4b
--- /dev/null
+++ b/appl/collab/clients/chat.b
@@ -0,0 +1,224 @@
+implement Chat;
+
+include "sys.m";
+	sys: Sys;
+
+include "draw.m";
+	draw: Draw;
+
+include "tk.m";
+	tk: Tk;
+
+include "tkclient.m";
+	tkclient: Tkclient;
+
+Chat: module {
+	init: fn(ctxt: ref Draw->Context, args: list of string);
+};
+
+stderr: ref Sys->FD;
+
+tksetup := array [] of {
+	"frame .f",
+	"text .f.t -state disabled -wrap word -yscrollcommand {.f.sb set}",
+	"scrollbar .f.sb -orient vertical -command {.f.t yview}",
+	"entry .e -bg white",
+	"bind .e <Key-\n> {send cmd send}",
+	"pack .f.sb -in .f -side left -fill y",
+	"pack .f.t -in .f -side left -fill both -expand 1",
+	"pack .f -side top -fill both -expand 1",
+	"pack .e -side bottom -fill x",
+	"pack propagate . 0",
+	"update",
+};
+
+init(ctxt: ref Draw->Context, args: list of string)
+{
+	sys = load Sys Sys->PATH;
+	sys->pctl(Sys->NEWPGRP, nil);
+	stderr = sys->fildes(2);
+
+	draw = load Draw Draw->PATH;
+	if (draw == nil)
+		badmodule(Draw->PATH);
+
+	tk = load Tk Tk->PATH;
+	if (tk == nil)
+		badmodule(Tk->PATH);
+
+	tkclient = load Tkclient Tkclient->PATH;
+	if (tkclient == nil)
+		badmodule(Tkclient->PATH);
+
+
+	if (len args < 2) {
+		sys->fprint(stderr, "usage: chat [servicedir] room\n");
+		raise "fail:init";
+	}
+	args = tl args;
+
+	servicedir := "/n/remote/services";
+	if(len args == 2)
+		(servicedir, args) = (hd args, tl args);
+	room := hd args;
+
+	tkclient->init();
+	(win, winctl) := tkclient->toplevel(ctxt, nil, sys->sprint("Chat %s", room), Tkclient->Appl);
+
+	cmd := chan of string;
+	tk->namechan(win, cmd, "cmd");
+	tkcmds(win, tksetup);
+	tkcmd(win, ". configure -height 300");
+	fittoscreen(win);
+	tkclient->onscreen(win, nil);
+	tkclient->startinput(win, "kbd"::"ptr"::nil);
+
+	msgs := chan of string;
+	conn := chan of (string, ref Sys->FD);
+	spawn connect(servicedir, room, msgs, conn);
+	msgsfd: ref Sys->FD;
+
+	for (;;) alt {
+	(e, fd) := <-conn =>
+		if (msgsfd == nil) {
+			if (e == nil) {
+				output(win, "*** connected");
+				msgsfd = fd;
+			} else
+				output(win, "*** " + e);
+		} else {
+			output(win, "*** disconnected");
+			msgsfd = nil;
+		}
+
+	txt := <-msgs =>
+		output(win, txt);
+
+	<- cmd =>
+		msg := tkcmd(win, ".e get");
+		if (msgsfd != nil && msg != nil) {
+			tkcmd(win, ".f.t see end");
+			tkcmd(win, ".e delete 0 end");
+			tkcmd(win, "update");
+			d := array of byte msg;
+			sys->write(msgsfd, d, len d);
+		}
+
+	s := <-win.ctxt.kbd =>
+		tk->keyboard(win, s);
+	s := <-win.ctxt.ptr =>
+		tk->pointer(win, *s);
+	s := <-win.ctxt.ctl or
+	s = <-win.wreq or
+	s = <-winctl =>
+		tkclient->wmctl(win, s);
+	}
+}
+
+err(s: string)
+{
+	sys->fprint(stderr, "chat: %s\n", s);
+	raise "fail:err";
+}
+
+badmodule(path: string)
+{
+	err(sys->sprint("can't load module %s: %r", path));
+}
+
+tkcmds(t: ref Tk->Toplevel, cmds: array of string)
+{
+	for (i := 0; i < len cmds; i++)
+		tkcmd(t, cmds[i]);
+}
+
+tkcmd(t: ref Tk->Toplevel, cmd: string): string
+{
+	s := tk->cmd(t, cmd);
+	if (s != nil && s[0] == '!')
+		sys->fprint(stderr, "chat: tk error: %s [%s]\n", s, cmd);
+	return s;
+}
+
+connect(dir, name: string, msgs: chan of string, conn: chan of (string, ref Sys->FD))
+{
+	(ctlfd, srvdir, emsg) := opensvc(dir, "chat", name);
+	if(ctlfd == nil) {
+		conn <-= (emsg, nil);
+		return;
+	}
+	srvpath := srvdir+"/msgs";
+	msgsfd := sys->open(srvpath, Sys->ORDWR);
+	if(msgsfd == nil) {
+		conn <-= (sys->sprint("internal error: can't open %s: %r", srvpath), nil);
+		return;
+	}
+	conn <-= (nil, msgsfd);
+	buf := array[Sys->ATOMICIO] of byte;
+	while((n := sys->read(msgsfd, buf, len buf)) > 0)
+		msgs <-= string buf[0:n];
+	conn <-= (nil, nil);
+}
+
+opensvc(dir: string, svc: string, name: string): (ref Sys->FD, string, string)
+{
+	ctlfd := sys->open(dir+"/ctl", Sys->ORDWR);
+	if(ctlfd == nil)
+		return (nil, nil, sys->sprint("can't open %s/ctl: %r", dir));
+	if(sys->fprint(ctlfd, "%s %s", svc, name) <= 0)
+		return (nil, nil, sys->sprint("can't access %s service %s: %r", svc, name));
+	buf := array [32] of byte;
+	sys->seek(ctlfd, big 0, Sys->SEEKSTART);
+	n := sys->read(ctlfd, buf, len buf);
+	if (n <= 0)
+		return (nil, nil, sys->sprint("%s/ctl: protocol error: %r", dir));
+	return (ctlfd, dir+"/"+string buf[0:n], nil);
+}
+
+firstmsg := 1;
+output(win: ref Tk->Toplevel, txt: string)
+{
+	if (firstmsg)
+		firstmsg = 0;
+	else
+		txt = "\n" + txt;
+	yview := tkcmd(win, ".f.t yview");
+	(nil, toks) := sys->tokenize(yview, " ");
+	toks = tl toks;
+
+	tkcmd(win, ".f.t insert end '" + txt);
+	if (hd toks == "1")
+		tkcmd(win, ".f.t see end");
+	tkcmd(win, "update");
+}
+
+KEYBOARDH: con 90;
+
+fittoscreen(win: ref Tk->Toplevel)
+{
+	Point, Rect: import draw;
+	if (win.image == nil || win.image.screen == nil)
+		return;
+	r := win.image.screen.image.r;
+	scrsize := Point((r.max.x - r.min.x), (r.max.y - r.min.y)- KEYBOARDH);
+	bd := int tkcmd(win, ". cget -bd");
+	winsize := Point(int tkcmd(win, ". cget -actwidth") + bd * 2, int tkcmd(win, ". cget -actheight") + bd * 2);
+	if (winsize.x > scrsize.x)
+		tkcmd(win, ". configure -width " + string (scrsize.x - bd * 2));
+	if (winsize.y > scrsize.y)
+		tkcmd(win, ". configure -height " + string (scrsize.y - bd * 2));
+	actr: Rect;
+	actr.min = Point(int tkcmd(win, ". cget -actx"), int tkcmd(win, ". cget -acty"));
+	actr.max = actr.min.add((int tkcmd(win, ". cget -actwidth") + bd*2,
+				int tkcmd(win, ". cget -actheight") + bd*2));
+	(dx, dy) := (actr.dx(), actr.dy());
+	if (actr.max.x > r.max.x)
+		(actr.min.x, actr.max.x) = (r.min.x - dx, r.max.x - dx);
+	if (actr.max.y > r.max.y)
+		(actr.min.y, actr.max.y) = (r.min.y - dy, r.max.y - dy);
+	if (actr.min.x < r.min.x)
+		(actr.min.x, actr.max.x) = (r.min.x, r.min.x + dx);
+	if (actr.min.y < r.min.y)
+		(actr.min.y, actr.max.y) = (r.min.y, r.min.y + dy);
+	tkcmd(win, ". configure -x " + string actr.min.x + " -y " + string actr.min.y);
+}
diff --git a/appl/collab/clients/poll.b b/appl/collab/clients/poll.b
new file mode 100644
index 00000000..ffb79c73
--- /dev/null
+++ b/appl/collab/clients/poll.b
@@ -0,0 +1,282 @@
+implement Poll;
+
+include "sys.m";
+	sys: Sys;
+
+include "draw.m";
+
+include "tk.m";
+	tk: Tk;
+
+include "tkclient.m";
+	tkclient: Tkclient;
+
+include "dialog.m";
+	dialog: Dialog;
+
+include "arg.m";
+
+Poll: module
+{
+	init:	fn(nil: ref Draw->Context, nil: list of string);
+};
+
+Maxanswer: con 4;
+
+contents := array[] of {
+	"frame .f",
+	"frame .a",
+	"radiobutton .a.a1 -state disabled -variable answer -value A -text {A} -command {send entry A}",
+	"radiobutton .a.a2 -state disabled -variable answer -value B -text {B} -command {send entry B}",
+	"radiobutton .a.a3 -state disabled -variable answer -value C -text {C} -command {send entry C}",
+	"radiobutton .a.a4 -state disabled -variable answer -value D -text {D} -command {send entry D}",
+	"pack .a.a1 -side top -fill x -expand 1",
+	"pack .a.a2 -side top -fill x -expand 1",
+	"pack .a.a3 -side top -fill x -expand 1",
+	"pack .a.a4 -side top -fill x -expand 1",
+	"pack .a -side top -fill both -expand 1",
+	"pack .f -side top -fill both",
+};
+
+dbcontents := array[] of {
+	"text .f.t -state disabled -wrap word -yscrollcommand {.f.sb set} -height 4h",
+	"scrollbar .f.sb -orient vertical -command {.f.t yview}",
+	"pack .f.sb -side left -fill y",
+	"pack .f.t -side left -fill both -expand 1",
+};
+
+usage()
+{
+	sys->fprint(sys->fildes(2), "usage: poll [-d] [servicedir] pollname\n");
+	raise "fail:usage";
+}
+
+init(ctxt: ref Draw->Context, args: list of string)
+{
+	sys = load Sys Sys->PATH;
+	tk = load Tk Tk->PATH;
+	tkclient = load Tkclient Tkclient->PATH;
+	dialog = load Dialog Dialog->PATH;
+
+	arg := load Arg Arg->PATH;
+	if(arg == nil){
+		sys->fprint(sys->fildes(2), "poll: can't load %s: %r\n", Arg->PATH);
+		raise "fail:load";
+	}
+	arg->init(args);
+	debug := 0;
+	while((ch := arg->opt()) != 0)
+		case ch {
+		'd' =>
+			debug = 1;
+		* =>
+			usage();
+		}
+	args = arg->argv();
+	arg = nil;
+	if(len args < 1)
+		usage();
+	sys->pctl(Sys->NEWPGRP, nil);
+
+	servicedir := "/n/remote/services";
+	if(len args == 2)
+		(servicedir, args) = (hd args, tl args);
+	pollname := hd args;
+
+	(cfd, dir, emsg) := opensvc(servicedir, "mpx", pollname);
+	if(cfd == nil){
+		sys->fprint(sys->fildes(2), "poll: can't access poll %s: %s\n", pollname, emsg);
+		raise "fail:error";
+	}
+	fd := sys->open(dir+"/leaf", Sys->ORDWR);
+	if(fd == nil){
+		sys->fprint(sys->fildes(2), "poll: can't open %s/leaf: %r\n", dir);
+		raise "fail:open";
+	}
+
+	tkclient->init();
+	dialog->init();
+	(frame, wmctl) := tkclient->toplevel(ctxt, nil, sys->sprint("Poll %s", pollname), Tkclient->Appl);
+	entry := chan of string;
+	tk->namechan(frame, entry, "entry");
+	tkcmds(frame, contents);
+	if(debug)
+		tkcmds(frame, dbcontents);
+	tkcmd(frame, "pack propagate . 0");
+	fittoscreen(frame);
+	tk->cmd(frame, "update");
+	tkclient->onscreen(frame, nil);
+	tkclient->startinput(frame, "kbd"::"ptr"::nil);
+
+	in := chan of string;
+	spawn reader(fd, in);
+	first := 1;
+	lastval := -1;
+	qno := -1;
+	for(;;)
+		alt{
+		s := <-frame.ctxt.kbd =>
+			tk->keyboard(frame, s);
+		s := <-frame.ctxt.ptr =>
+			tk->pointer(frame, *s);
+		s := <-frame.ctxt.ctl or
+		s = <-frame.wreq or
+		s = <-wmctl =>
+			tkclient->wmctl(frame, s);
+
+		msg := <-entry =>
+			if(fd == nil){
+				dialog->prompt(ctxt, frame.image, "error -fg red", "Error", "Lost connection to polling station", 0, "Dismiss"::nil);
+				break;
+			}
+			n := msg[0]-'A';
+			lastval = n;
+			selectonly(frame, n, Maxanswer, "disabled");
+			if(qno >= 0) {
+				# send our answer to the polling station
+				if(sys->fprint(fd, "%d %s", qno, msg) < 0){
+					sys->fprint(sys->fildes(2), "poll: write error: %r\n");
+					fd = nil;
+				}
+				qno = -1;	# only one go at it
+			}
+
+		s := <-in =>
+			if(s != nil){
+				if(debug){
+					t := s;
+					if(!first)
+						t = "\n"+t;
+					first = 0;
+					tk->cmd(frame, ".f.t insert end '" + t);
+					tk->cmd(frame, ".f.t see end");
+					tk->cmd(frame, "update");
+				}
+				(nf, flds) := sys->tokenize(s, " ");
+				if(nf > 1 && hd flds == "error:"){
+					dialog->prompt(ctxt, frame.image, "error -fg red", "Error", sys->sprint("polling station reports: %s", s), 0, "Dismiss"::nil);
+					break;
+				}
+				if(nf < 4)
+					break;
+				# seq clientid op name data
+				op, name: string;
+				flds = tl flds;	# ignore seq
+				flds = tl flds;	# ignore clientid
+				(op, flds) = (hd flds, tl flds);
+				(name, flds) = (hd flds, tl flds);
+				case op {
+				"M" =>
+					# poll qno nanswer opt
+					# stop qno
+					selectonly(frame, -1, Maxanswer, "disabled");
+					if(len flds < 2)
+						break;
+					(op, flds) = (hd flds, tl flds);
+					(s, flds) = (hd flds, tl flds);
+					case op {
+					"poll" =>
+						qno = int s;
+						(s, flds) = (hd flds, tl flds);
+						n := int s;
+						if(n > Maxanswer)
+							n = Maxanswer;
+						if(n < 2)
+							n = 2;
+						selectonly(frame, -1, n, "normal");
+						lastval = -1;
+					"stop" =>
+						selectonly(frame, lastval, Maxanswer, "disabled");
+					}
+				"L" =>
+					dialog->prompt(ctxt, frame.image, "error -fg red", "Notice", sys->sprint("Poller (%s) has gone", name), 0, "Exit"::nil);
+					tkclient->wmctl(frame, "exit");
+				}
+			}else{
+				dialog->prompt(ctxt, frame.image, "error -fg red", "Notice", "Polling station closed", 0, "Exit"::nil);
+				tkclient->wmctl(frame, "exit");
+			}
+		}
+}
+
+selectonly(t: ref Tk->Toplevel, n: int, top: int, state: string)
+{
+	for(i := 0; i < top; i++){
+		path := sys->sprint(".a.a%d", i+1);
+		if(i != n)
+			tkcmd(t, path+" deselect");
+		else
+			tkcmd(t, path+" select");
+		tkcmd(t, path+" configure -state "+state);
+	}
+	tk->cmd(t, "update");
+}
+
+reader(fd: ref Sys->FD, c: chan of string)
+{
+	buf := array[Sys->ATOMICIO] of byte;
+	while((n := sys->read(fd, buf, len buf)) > 0)
+		c <-= string buf[0:n];
+	if(n < 0)
+		c <-= sys->sprint("error: %r");
+	c <-= nil;
+}
+
+opensvc(dir: string, svc: string, name: string): (ref Sys->FD, string, string)
+{
+	ctlfd := sys->open(dir+"/ctl", Sys->ORDWR);
+	if(ctlfd == nil)
+		return (nil, nil, sys->sprint("can't open %s/ctl: %r", dir));
+	if(sys->fprint(ctlfd, "%s %s", svc, name) <= 0)
+		return (nil, nil, sys->sprint("can't access %s service %s: %r", svc, name));
+	buf := array [32] of byte;
+	sys->seek(ctlfd, big 0, Sys->SEEKSTART);
+	n := sys->read(ctlfd, buf, len buf);
+	if (n <= 0)
+		return (nil, nil, sys->sprint("%s/ctl: protocol error: %r", dir));
+	return (ctlfd, dir+"/"+string buf[0:n], nil);
+}
+
+tkcmds(t: ref Tk->Toplevel, cmds: array of string)
+{
+	for (i := 0; i < len cmds; i++)
+		tkcmd(t, cmds[i]);
+}
+
+tkcmd(t: ref Tk->Toplevel, cmd: string): string
+{
+	s := tk->cmd(t, cmd);
+	if (s != nil && s[0] == '!')
+		sys->fprint(sys->fildes(2), "poll: tk error: %s [%s]\n", s, cmd);
+	return s;
+}
+
+fittoscreen(win: ref Tk->Toplevel)
+{
+	draw := load Draw Draw->PATH;
+	Point, Rect: import draw;
+	if (win.image == nil || win.image.screen == nil)
+		return;
+	r := win.image.screen.image.r;
+	scrsize := Point((r.max.x - r.min.x), (r.max.y - r.min.y));
+	bd := int tkcmd(win, ". cget -bd");
+	winsize := Point(int tkcmd(win, ". cget -actwidth") + bd * 2, int tkcmd(win, ". cget -actheight") + bd * 2);
+	if (winsize.x > scrsize.x)
+		tkcmd(win, ". configure -width " + string (scrsize.x - bd * 2));
+	if (winsize.y > scrsize.y)
+		tkcmd(win, ". configure -height " + string (scrsize.y - bd * 2));
+	actr: Rect;
+	actr.min = Point(int tkcmd(win, ". cget -actx"), int tkcmd(win, ". cget -acty"));
+	actr.max = actr.min.add((int tkcmd(win, ". cget -actwidth") + bd*2,
+				int tkcmd(win, ". cget -actheight") + bd*2));
+	(dx, dy) := (actr.dx(), actr.dy());
+	if (actr.max.x > r.max.x)
+		(actr.min.x, actr.max.x) = (r.min.x - dx, r.max.x - dx);
+	if (actr.max.y > r.max.y)
+		(actr.min.y, actr.max.y) = (r.min.y - dy, r.max.y - dy);
+	if (actr.min.x < r.min.x)
+		(actr.min.x, actr.max.x) = (r.min.x, r.min.x + dx);
+	if (actr.min.y < r.min.y)
+		(actr.min.y, actr.max.y) = (r.min.y, r.min.y + dy);
+	tkcmd(win, ". configure -x " + string actr.min.x + " -y " + string actr.min.y);
+}
diff --git a/appl/collab/clients/poller.b b/appl/collab/clients/poller.b
new file mode 100644
index 00000000..90365606
--- /dev/null
+++ b/appl/collab/clients/poller.b
@@ -0,0 +1,330 @@
+implement Poller;
+
+include "sys.m";
+	sys: Sys;
+
+include "draw.m";
+	draw: Draw;
+	Rect, Point: import draw;
+
+include "tk.m";
+	tk: Tk;
+
+include "tkclient.m";
+	tkclient: Tkclient;
+
+include "dialog.m";
+	dialog: Dialog;
+
+include "arg.m";
+
+Poller: module
+{
+	init:	fn(nil: ref Draw->Context, nil: list of string);
+};
+
+Maxanswer: con 4;	# Tk below isn't parametrised, but could be
+
+contents := array[] of {
+	"frame .f",
+	"frame .f.n",
+	"label .f.l -anchor nw -text {Number of answers: }",
+	"radiobutton .f.n.a2 -text {2} -variable nanswer -value 2",
+	"radiobutton .f.n.a3 -text {3} -variable nanswer -value 3",
+	"radiobutton .f.n.a4 -text {4} -variable nanswer -value 4",
+	"pack .f.n.a2 .f.n.a3 .f.n.a4 -side left",
+
+	"frame .f.b",
+	"button .f.b.start -text {Start} -command {send cmd start}",
+	"button .f.b.stop -text {Stop} -state disabled -command {send cmd stop}",
+	"pack .f.b.start .f.b.stop -side left",
+
+	"canvas .f.c -height 230 -width 200",
+
+	"pack .f.l -side top -fill x",
+	"pack .f.n -side top -fill x",
+	"pack .f.b -side top -fill x -expand 1",
+	"pack .f.c -side top -pady 2",
+	"pack .f -side top -fill both -expand 1",
+};
+
+dbcontents := array[] of {
+	"text .f.t -state disabled -wrap word -height 4h -yscrollcommand {.f.sb set}",	# message log
+	"scrollbar .f.sb -orient vertical -command {.f.t yview}",
+	"pack .f.sb -side left -fill y",
+	"pack .f.t -side left -fill both",
+};
+
+Bar: adt {
+	frame:	ref Tk->Toplevel;
+	canvas:	string;
+	border:	string;
+	inside:	string;
+	label:	string;
+	r:	Rect;
+	v:	real;
+
+	draw:	fn(nil: self ref Bar);
+};
+
+usage()
+{
+	sys->fprint(sys->fildes(2), "usage: poller [-d] [servicedir] pollname\n");
+	raise "fail:usage";
+}
+
+init(ctxt: ref Draw->Context, args: list of string)
+{
+	sys = load Sys Sys->PATH;
+	draw = load Draw Draw->PATH;
+	tk = load Tk Tk->PATH;
+	tkclient = load Tkclient Tkclient->PATH;
+	dialog = load Dialog Dialog->PATH;
+
+	arg := load Arg Arg->PATH;
+	if(arg == nil){
+		sys->fprint(sys->fildes(2), "poller: can't load %s: %r\n", Arg->PATH);
+		raise "fail:load";
+	}
+	arg->init(args);
+	debug := 0;
+	while((ch := arg->opt()) != 0)
+		case ch {
+		'd' =>
+			debug = 1;
+		* =>
+			usage();
+		}
+	args = arg->argv();
+	arg = nil;
+	if(len args < 1)
+		usage();
+	sys->pctl(Sys->NEWPGRP, nil);
+
+	servicedir := "/n/remote/services";
+	if(len args == 2)
+		(servicedir, args) = (hd args, tl args);
+	pollname := hd args;
+
+	(cfd, dir, emsg) := opensvc(servicedir, "mpx", pollname);
+	if(cfd == nil){
+		sys->fprint(sys->fildes(2), "poller: can't access polling station %s: %s\n", pollname, emsg);
+		raise "fail:error";
+	}
+	fd := sys->open(dir+"/root", Sys->ORDWR);
+	if(fd == nil){
+		sys->fprint(sys->fildes(2), "poller: can't open %s/root: %r\n", dir);
+		raise "fail:open";
+	}
+
+	tkclient->init();
+	dialog->init();
+	(frame, wmctl) := tkclient->toplevel(ctxt, nil, sys->sprint("Poller: %s", pollname), Tkclient->Appl);
+	cmd := chan of string;
+	tk->namechan(frame, cmd, "cmd");
+	tkcmds(frame, contents);
+	if(debug)
+		tkcmds(frame, dbcontents);
+	tkcmd(frame, "pack propagate . 0");
+	fittoscreen(frame);
+	tk->cmd(frame, "update");
+	tkclient->onscreen(frame, nil);
+	tkclient->startinput(frame, "kbd"::"ptr"::nil);
+
+	bars := mkbars(frame, ".f.c", Maxanswer);
+	count: array of int;
+
+	in := chan of string;
+	spawn reader(fd, in);
+	first := 1;
+	qno := 0;
+	nanswer := 0;
+	opt := 0;
+	total := 0;
+	for(;;)
+		alt{
+		s := <-frame.ctxt.kbd =>
+			tk->keyboard(frame, s);
+		s := <-frame.ctxt.ptr =>
+			tk->pointer(frame, *s);
+		s := <-frame.ctxt.ctl or
+		s = <-frame.wreq or
+		s = <-wmctl =>
+			tkclient->wmctl(frame, s);
+
+		c := <-cmd =>
+			if(fd == nil){
+				dialog->prompt(ctxt, frame.image, "error -fg red", "Error", "Lost connection to polling station", 0, "Dismiss"::nil);
+				break;
+			}
+			case c {
+			"start" =>
+				s := tkcmd(frame, "variable nanswer");
+				if(s == nil || s[0] == '!'){
+					dialog->prompt(ctxt, frame.image, "error -fg red", "Error", "Please select number of answers", 0, "Ok"::nil);
+					break;
+				}
+				nanswer = int s;
+				count = array[Maxanswer] of {* => 0};
+				total = 0;
+				qno++;
+				#opt = (int tkcmd(frame, "variable none") << 1) | int tkcmd(frame, "variable all");
+				tkcmd(frame, ".f.b.start configure -state disabled");
+				tkcmd(frame, ".f.b.stop configure -state normal");
+				if(sys->fprint(fd, "poll %d %d %d", qno, nanswer, opt) <= 0)
+					sys->fprint(sys->fildes(2), "poller: write error: %r\n");
+			"stop" =>
+				tkcmd(frame, ".f.b.stop configure -state disabled");
+				tkcmd(frame, "update");
+				if(sys->fprint(fd, "stop %d", qno) <= 0)
+					sys->fprint(sys->fildes(2), "poller: write error: %r\n");
+				# stop ...
+				tkcmd(frame, ".f.b.start configure -state normal");
+			}
+			tk->cmd(frame, "update");
+
+		s := <-in =>
+			if(s != nil){
+				if(debug){
+					t := s;
+					if(!first)
+						t = "\n"+t;
+					first = 0;
+					tkcmd(frame, ".f.t insert end '" + t);
+					tkcmd(frame, ".f.t see end");
+					tkcmd(frame, "update");
+				}
+				r := getresult(s, qno);
+				if(r < 0)
+					break;
+				if(r >= 0 && r < len count){
+					count[r]++;
+					total++;
+					for(i:=0; i < len count; i++){
+						bars[i].v = real count[i]/real total;
+						bars[i].draw();
+					}
+					tk->cmd(frame, "update");
+				}
+				#sys->print("%d %d\n", qno, r);
+			}else
+				fd = nil;
+		}
+}
+
+mkbars(t: ref Tk->Toplevel, canvas: string, nbars: int): array of ref Bar
+{
+	x := 0;
+	a := array[nbars] of ref Bar;
+	for(i := 0; i < nbars; i++){
+		b := ref Bar(t, canvas, nil, nil, nil, Rect((x,2),(x+20,202)), 0.0);
+		b.border = tkcmd(t, sys->sprint("%s create rectangle %d %d %d %d",
+			canvas, b.r.min.x,b.r.min.y,b.r.max.x,b.r.max.y));
+		r := b.r.inset(1);
+		b.inside = tkcmd(t, sys->sprint("%s create rectangle %d %d %d %d -fill red",
+			canvas, r.max.x, r.max.y,r.max.x,r.max.y));
+		b.label = tkcmd(t, sys->sprint("%s create text %d %d -justify center -anchor n -text '0%%",
+			canvas, (r.min.x+r.max.x)/2, r.max.y+4));
+		a[i] = b;
+		x += 50;
+	}
+	tk->cmd(t, "update");
+	return a;
+}
+
+Bar.draw(b: self ref Bar)
+{
+	r := b.r.inset(2);
+	y := r.max.y - int (b.v * real r.dy());
+	tkcmd(b.frame, sys->sprint("%s coords %s %d %d %d %d",
+		b.canvas, b.inside, r.min.x, y, r.max.x, r.max.y));
+	tkcmd(b.frame, sys->sprint("%s itemconfigure %s -text '%.0f%%",
+		b.canvas, b.label, b.v*100.0));
+}
+
+getresult(msg: string, qno: int): int
+{
+	(nf, flds) := sys->tokenize(msg, " ");
+	if(nf < 5 || hd flds == "error:")
+		return -1;	# not of interest
+	op := hd tl tl flds;
+	flds = tl tl tl flds;
+	if(op != "m")
+		return -1; # not a message from leaf
+	if(len flds < 3)
+		return -1;	# bad format
+	flds = tl flds;	# ignore user name
+	if(int hd flds != qno)
+		return -1;	# not current question
+	result := hd tl flds;
+	if(result[0] >= 'A' && result[0] <= 'D')
+		return result[0]-'A';
+	return -1;
+}
+	
+reader(fd: ref Sys->FD, c: chan of string)
+{
+	buf := array[Sys->ATOMICIO] of byte;
+	while((n := sys->read(fd, buf, len buf)) > 0)
+		c <-= string buf[0:n];
+	if(n < 0)
+		c <-= sys->sprint("error: %r");
+	c <-= nil;
+}
+
+opensvc(dir: string, svc: string, name: string): (ref Sys->FD, string, string)
+{
+	ctlfd := sys->open(dir+"/ctl", Sys->ORDWR);
+	if(ctlfd == nil)
+		return (nil, nil, sys->sprint("can't open %s/ctl: %r", dir));
+	if(sys->fprint(ctlfd, "%s %s", svc, name) <= 0)
+		return (nil, nil, sys->sprint("can't access %s service %s: %r", svc, name));
+	buf := array [32] of byte;
+	sys->seek(ctlfd, big 0, Sys->SEEKSTART);
+	n := sys->read(ctlfd, buf, len buf);
+	if (n <= 0)
+		return (nil, nil, sys->sprint("%s/ctl: protocol error: %r", dir));
+	return (ctlfd, dir+"/"+string buf[0:n], nil);
+}
+
+tkcmds(t: ref Tk->Toplevel, cmds: array of string)
+{
+	for (i := 0; i < len cmds; i++)
+		tkcmd(t, cmds[i]);
+}
+
+tkcmd(t: ref Tk->Toplevel, cmd: string): string
+{
+	s := tk->cmd(t, cmd);
+	if (s != nil && s[0] == '!')
+		sys->fprint(sys->fildes(2), "poller: tk error: %s [%s]\n", s, cmd);
+	return s;
+}
+
+fittoscreen(win: ref Tk->Toplevel)
+{
+	if (win.image == nil || win.image.screen == nil)
+		return;
+	r := win.image.screen.image.r;
+	scrsize := Point((r.max.x - r.min.x), (r.max.y - r.min.y));
+	bd := int tkcmd(win, ". cget -bd");
+	winsize := Point(int tkcmd(win, ". cget -actwidth") + bd * 2, int tkcmd(win, ". cget -actheight") + bd * 2);
+	if (winsize.x > scrsize.x)
+		tkcmd(win, ". configure -width " + string (scrsize.x - bd * 2));
+	if (winsize.y > scrsize.y)
+		tkcmd(win, ". configure -height " + string (scrsize.y - bd * 2));
+	actr: Rect;
+	actr.min = Point(int tkcmd(win, ". cget -actx"), int tkcmd(win, ". cget -acty"));
+	actr.max = actr.min.add((int tkcmd(win, ". cget -actwidth") + bd*2,
+				int tkcmd(win, ". cget -actheight") + bd*2));
+	(dx, dy) := (actr.dx(), actr.dy());
+	if (actr.max.x > r.max.x)
+		(actr.min.x, actr.max.x) = (r.min.x - dx, r.max.x - dx);
+	if (actr.max.y > r.max.y)
+		(actr.min.y, actr.max.y) = (r.min.y - dy, r.max.y - dy);
+	if (actr.min.x < r.min.x)
+		(actr.min.x, actr.max.x) = (r.min.x, r.min.x + dx);
+	if (actr.min.y < r.min.y)
+		(actr.min.y, actr.max.y) = (r.min.y, r.min.y + dy);
+	tkcmd(win, ". configure -x " + string actr.min.x + " -y " + string actr.min.y);
+}
diff --git a/appl/collab/clients/whiteboard.b b/appl/collab/clients/whiteboard.b
new file mode 100644
index 00000000..e05e1b45
--- /dev/null
+++ b/appl/collab/clients/whiteboard.b
@@ -0,0 +1,586 @@
+implement Whiteboard;
+
+include "sys.m";
+	sys: Sys;
+
+include "draw.m";
+	draw: Draw;
+	Screen, Display, Image, Rect, Point, Font: import draw;
+
+include "tk.m";
+	tk: Tk;
+
+include "tkclient.m";
+	tkclient: Tkclient;
+
+Whiteboard: module {
+	init: fn(ctxt: ref Draw->Context, args: list of string);
+};
+
+ERASEWIDTH: con 6;
+
+
+stderr: ref Sys->FD;
+srvfd: ref Sys->FD;
+disp: ref Display;
+font: ref Draw->Font;
+drawctxt: ref Draw->Context;
+
+tksetup := array[] of {
+	"frame .f -bd 2",
+	"frame .c -bg white -width 234 -height 279",
+	"menu .penmenu",
+	".penmenu add command -command {send cmd pen 0} -bitmap @/icons/whiteboard/0.bit",
+	".penmenu add command -command {send cmd pen 1} -bitmap @/icons/whiteboard/1.bit",
+	".penmenu add command -command {send cmd pen 2} -bitmap @/icons/whiteboard/2.bit",
+	".penmenu add command -command {send cmd pen erase} -bitmap @/icons/whiteboard/erase.bit",
+	"menubutton .pen -menu .penmenu -bitmap @/icons/whiteboard/1.bit",
+	"button .colour -bg black -activebackground black -command {send cmd getcolour}",
+	"pack .c -in .f",
+	"pack .f -side top -anchor center",
+	"pack .pen -side left",
+	"pack .colour -side left -fill both -expand 1",
+	"update",
+};
+
+tkconnected := array[] of {
+	"bind .c <Button-1> {send cmd down %x %y}",
+	"bind .c <ButtonRelease-1> {send cmd up %x %y}",
+	"update",
+};
+
+init(ctxt: ref Draw->Context, args: list of string)
+{
+	sys = load Sys Sys->PATH;
+	sys->pctl(Sys->NEWPGRP, nil);
+	stderr = sys->fildes(2);
+
+	draw = load Draw Draw->PATH;
+	tk = load Tk Tk->PATH;
+
+	tkclient = load Tkclient Tkclient->PATH;
+	if (tkclient == nil)
+		badmod(Tkclient->PATH);
+
+	if (len args < 2) {
+		sys->fprint(stderr, "Usage: whiteboard [servicedir] id\n");
+		raise "fail:init";
+	}
+
+	args = tl args;
+	servicedir := "/n/remote/services";
+	if(len args == 2)
+		(servicedir, args) = (hd args, tl args);
+	wbid := hd args;
+
+	disp = ctxt.display;
+	if (disp == nil) {
+		sys->fprint(stderr, "bad Draw->Context\n");
+		raise "fail:init";
+	}
+	drawctxt = ctxt;
+
+	tkclient->init();
+	(win, winctl) := tkclient->toplevel(ctxt, nil, "Whiteboard", 0);
+	font = Font.open(disp, tkcmd(win, ". cget -font"));
+	if(font == nil)
+		font = Font.open(disp, "*default*");
+	cmd := chan of string;
+	tk->namechan(win, cmd, "cmd");
+	tkcmds(win, tksetup);
+	tkclient->onscreen(win, nil);
+	tkclient->startinput(win, "kbd" :: "ptr" :: nil);
+	cimage := makeimage(win);
+
+	sc := chan of array of (Point, Point);
+	cc := chan of (string, ref Image, ref Sys->FD, ref Sys->FD);
+	connected := 0;
+	sfd: ref Sys->FD;
+	ctlfd: ref Sys->FD;	# must keep this open to keep service active
+
+	showtext(cimage, "connecting...");
+	spawn connect(servicedir, wbid, cc);
+
+	err: string;
+	strokeimg: ref Image;
+Connect:
+	for (;;) alt {
+	(err, strokeimg, sfd, ctlfd) = <-cc =>
+		if (err == nil)
+			break Connect;
+		else
+			showtext(cimage, "Error: " + err);
+
+	s := <-winctl or
+	s = <-win.wreq or
+	s = <-win.ctxt.ctl =>
+		oldimg := win.image;
+		err = tkclient->wmctl(win, s);
+		if(s[0] == '!' && err == nil && win.image != oldimg){
+			cimage = makeimage(win);
+			showtext(cimage, "connecting...");
+		}
+	p := <-win.ctxt.ptr =>
+		tk->pointer(win, *p);
+	c := <-win.ctxt.kbd =>
+		tk->keyboard(win, c);
+	}
+
+	tkcmd(win, ".c configure -width " + string strokeimg.r.dx());
+	tkcmd(win, ".c configure -height " + string strokeimg.r.dy());
+	tkcmds(win, tkconnected);
+	tkcmd(win, "update");
+	cimage.draw(cimage.r, strokeimg, nil, strokeimg.r.min);
+
+	strokesin := chan of (int, int, array of Point);
+	strokesout := chan of (int, int, Point, Point);
+	spawn reader(sfd, strokesin);
+	spawn writer(sfd, strokesout);
+
+	pendown := 0;
+	p0, p1: Point;
+
+	getcolour := 0;
+	white := disp.white;
+	whitepen := disp.newimage(Rect(Point(0,0), Point(1,1)), Draw->CMAP8, 1, Draw->White);
+	pencolour := Draw->Black;
+	penwidth := 1;
+	erase := 0;
+	drawpen := disp.newimage(Rect(Point(0,0), Point(1,1)), Draw->CMAP8, 1, pencolour);
+
+	for (;;) alt {
+	s := <-winctl or
+	s = <-win.ctxt.ctl or
+	s = <-win.wreq =>
+		oldimg := win.image;
+		err = tkclient->wmctl(win, s);
+		if(s[0] == '!' && err == nil && win.image != oldimg){
+			cimage = makeimage(win);
+			cimage.draw(cimage.r, strokeimg, nil, strokeimg.r.min);
+		}
+	p := <-win.ctxt.ptr =>
+		tk->pointer(win, *p);
+	c := <-win.ctxt.kbd =>
+		tk->keyboard(win, c);
+	(colour, width, strokes) := <-strokesin =>
+		if (strokes == nil)
+			tkclient->settitle(win, "Whiteboard (Disconnected)");
+		else {
+			pen := disp.newimage(Rect(Point(0,0), Point(1,1)), Draw->CMAP8, 1, colour);
+			drawstrokes(cimage, cimage.r.min, pen, width, strokes);
+			drawstrokes(strokeimg, strokeimg.r.min, pen, width, strokes);
+		}
+
+	c := <-cmd =>
+		(nil, toks) := sys->tokenize(c, " ");
+		case hd toks {
+		"down" =>
+			toks = tl toks;
+			x := int hd toks;
+			y := int hd tl toks;
+			if (!pendown) {
+				pendown = 1;
+				p0 = Point(x, y);
+				continue;
+			}
+			p1 = Point(x, y);
+			if (p1.x == p0.x && p1.y == p0.y)
+				continue;
+			pen := drawpen;
+			colour := pencolour;
+			width := penwidth;
+			if (erase) {
+				pen = whitepen;
+				colour = Draw->White;
+				width = ERASEWIDTH;
+			}
+			drawstroke(cimage, cimage.r.min, p0, p1, pen, width);
+			drawstroke(strokeimg, strokeimg.r.min, p0, p1, pen, width);
+			strokesout <-= (colour, width, p0, p1);
+			p0 = p1;
+		"up" =>
+			pendown = 0;
+
+		"getcolour" =>
+			pendown = 0;
+			if (!getcolour)
+				spawn colourmenu(cmd);
+		"colour" =>
+			pendown = 0;
+			getcolour = 0;
+			toks = tl toks;
+			if (toks == nil)
+				# colourmenu was dismissed
+				continue;
+			erase = 0;
+			tkcmd(win, ".pen configure -bitmap @/icons/whiteboard/" + string penwidth + ".bit");
+			tkcmd(win, "update");
+			pencolour = int hd toks;
+			toks = tl toks;
+			tkcolour := hd toks;
+			drawpen = disp.newimage(Rect(Point(0,0), Point(1,1)), Draw->CMAP8, 1, pencolour);
+			tkcmd(win, ".colour configure -bg " + tkcolour + " -activebackground " + tkcolour);
+			tkcmd(win, "update");
+
+		"pen" =>
+			pendown = 0;
+			p := hd tl toks;
+			i := "";
+			if (p == "erase") {
+				erase = 1;
+				i = "erase.bit";
+			} else {
+				erase = 0;
+				penwidth = int p;
+				i = p + ".bit";
+			}
+			tkcmd(win, ".pen configure -bitmap @/icons/whiteboard/" + i);
+			tkcmd(win, "update");
+		}
+
+	}
+}
+
+makeimage(win: ref Tk->Toplevel): ref Draw->Image
+{
+	if(win.image == nil)
+		return nil;
+	scr := Screen.allocate(win.image, win.image.display.white, 0);
+	w := scr.newwindow(tk->rect(win, ".c", Tk->Local), Draw->Refnone, Draw->Nofill);
+	return w;
+}
+
+showtext(img: ref Image, s: string)
+{
+	r := img.r;
+	r.max.y = img.r.min.y + font.height;
+	img.draw(r, disp.white, nil, (0, 0));
+	img.text(r.min, disp.black, (0, 0), font, s);
+}
+
+penmenu(t: ref Tk->Toplevel, p: Point)
+{
+	topy := int tkcmd(t, ".penmenu yposition 0");
+	boty := int tkcmd(t, ".penmenu yposition end");
+	dy := boty - topy;
+	p.y -= dy;
+	tkcmd(t, ".penmenu post " + string p.x + " " + string p.y);
+}
+
+colourcmds := array[] of {
+	"label .l -height 10",
+	"frame .c -height 224 -width 224",
+	"pack .l -fill x -expand 1",
+	"pack .c -side bottom -fill both -expand 1",
+	"pack propagate . 0",
+	"bind .c <Button-1> {send cmd push %x %y}",
+	"bind .c <ButtonRelease-1> {send cmd release}",
+};
+
+lastcolour := "255";
+lasttkcolour := "#000000";
+
+colourmenu(c: chan of string)
+{
+	(t, winctl) := tkclient->toplevel(drawctxt, nil, "Whiteboard", Tkclient->OK);
+	cmd := chan of string;
+	tk->namechan(t, cmd, "cmd");
+	tkcmds(t, colourcmds);
+	tkcmd(t, ".l configure -bg " + lasttkcolour);
+	tkcmd(t, "update");
+	tkclient->onscreen(t, "onscreen");
+	tkclient->startinput(t, "kbd" :: "ptr" :: nil);
+
+	drawcolours(t.image, tk->rect(t, ".c", Tk->Local));
+
+	for(;;) alt {
+	p := <-t.ctxt.ptr =>
+		tk->pointer(t, *p);
+	s := <-t.ctxt.kbd =>
+		tk->keyboard(t, s);
+	s := <-winctl or
+	s = <-t.ctxt.ctl or
+	s = <-t.wreq =>
+		case s{
+		"ok" =>
+			c <-= "colour " + lastcolour + " " + lasttkcolour;
+			return;
+		"exit" =>
+			c <-= "colour";
+			return;
+		* =>
+			oldimage := t.image;
+			e := tkclient->wmctl(t, s);
+			if(s[0] == '!' && e == nil && oldimage != t.image)
+				drawcolours(t.image, tk->rect(t, ".c", Tk->Local));
+		}
+
+	press := <-cmd =>
+		(n, word) := sys->tokenize(press, " ");
+		case hd word {
+		"push" =>
+			(lastcolour, lasttkcolour) = color(int hd tl word, int hd tl tl word, tk->rect(t, ".c", 0).size());
+			tkcmd(t, ".l configure -bg " + lasttkcolour);
+		}
+	}
+}
+
+drawcolours(img: ref Image, cr: Rect)
+{
+	# use writepixels because it's much faster than allocating all those colors.
+	tmp := disp.newimage(((0,0),(cr.dx(),cr.dy()/16+1)), Draw->CMAP8, 0, 0);
+	if(tmp == nil)
+		return;
+	buf := array[tmp.r.dx()*tmp.r.dy()] of byte;
+	dx := cr.dx();
+	dy := cr.dy();
+	for(y:=0; y<16; y++){
+		for(i:=tmp.r.dx()-1; i>=0; --i)
+			buf[i] = byte (16*y+(16*i)/dx);
+		for(k:=tmp.r.dy()-1; k>=1; --k)
+			buf[dx*k:] = buf[0:dx];
+		tmp.writepixels(tmp.r, buf);
+		r: Rect;
+		r.min.x = cr.min.x;
+		r.max.x = cr.max.x;
+		r.min.y = cr.min.y+(dy*y)/16;
+		r.max.y = cr.min.y+(dy*(y+1))/16;
+		img.draw(r, tmp, nil, tmp.r.min);
+	}
+}
+
+color(x, y: int, size: Point): (string, string)
+{
+	x = (16*x)/size.x;
+	y = (16*y)/size.y;
+	col := 16*y+x;
+	(r, g, b) := disp.cmap2rgb(col);
+	tks := sys->sprint("#%.2x%.2x%.2x", r, g, b);
+	return (string disp.cmap2rgba(col), tks);
+}
+
+opensvc(dir: string, svc: string, name: string): (ref Sys->FD, string, string)
+{
+	ctlfd := sys->open(dir+"/ctl", Sys->ORDWR);
+	if(ctlfd == nil)
+		return (nil, nil, sys->sprint("can't open %s/ctl: %r", dir));
+	if(sys->fprint(ctlfd, "%s %s", svc, name) <= 0)
+		return (nil, nil, sys->sprint("can't access %s service %s: %r", svc, name));
+	buf := array [32] of byte;
+	sys->seek(ctlfd, big 0, Sys->SEEKSTART);
+	n := sys->read(ctlfd, buf, len buf);
+	if (n <= 0)
+		return (nil, nil, sys->sprint("%s/ctl: protocol error: %r", dir));
+	return (ctlfd, dir+"/"+string buf[0:n], nil);
+}
+
+connect(dir, name: string, res: chan of (string, ref Image, ref Sys->FD, ref Sys->FD))
+{
+	(ctlfd, srvdir, emsg) := opensvc(dir, "whiteboard", name);
+	if(ctlfd == nil) {
+		res <-= (emsg, nil, nil, nil);
+		return;
+	}
+
+	bitpath := srvdir + "/wb.bit";
+	strokepath := srvdir + "/strokes";
+
+	sfd := sys->open(strokepath, Sys->ORDWR);
+	if (sfd == nil) {
+		err := sys->sprint("cannot open whiteboard data: %r");
+		res <-= (err, nil, nil, nil);
+		srvfd = nil;
+		return;
+	}
+
+	bfd := sys->open(bitpath, Sys->OREAD);
+	if (bfd == nil) {
+		err := sys->sprint("cannot open whiteboard image: %r");
+		res <-= (err, nil, nil, nil);
+		srvfd = nil;
+		return;
+	}
+
+	img := disp.readimage(bfd);
+	if (img == nil) {
+		err := sys->sprint("cannot read whiteboard image: %r");
+		res <-= (err, nil, nil, nil);
+		srvfd = nil;
+		return;
+	}
+sys->print("read image ok\n");
+
+	# make sure image is depth 8 (because of image.line() bug)
+	if (img.depth != 8) {
+sys->print("depth is %d, not 8\n", img.depth);
+		nimg := disp.newimage(img.r, Draw->CMAP8, 0, 0);
+		if (nimg == nil) {
+			res <-= ("cannot allocate local image", nil, nil, nil);
+			srvfd = nil;
+			return;
+		}
+		nimg.draw(nimg.r, img, nil, img.r.min);
+		img = nimg;
+	}
+
+	res <-= (nil, img, sfd, ctlfd);
+}
+
+reader(fd: ref Sys->FD, sc: chan of (int, int, array of Point))
+{
+	buf := array [Sys->ATOMICIO] of byte;
+
+	for (;;) {
+		n := sys->read(fd, buf, len buf);
+		if (n <= 0) {
+			sc <-= (0, 0, nil);
+			return;
+		}
+		s := string buf[0:n];
+		(npts, toks) := sys->tokenize(s, " ");
+		if (npts & 1)
+			# something wrong
+			npts--;
+		if (npts < 6)
+			# ignore
+			continue;
+
+		colour, width: int;
+		(colour, toks) = (int hd toks, tl toks);
+		(width, toks) = (int hd toks, tl toks);
+		pts := array [(npts - 2)/ 2] of Point;
+		for (i := 0; toks != nil; i++) {
+			x, y: int;
+			(x, toks) = (int hd toks, tl toks);
+			(y, toks) = (int hd toks, tl toks);
+			pts[i] = Point(x, y);
+		}
+		sc <-= (colour, width, pts);
+		pts = nil;
+	}
+}
+
+Wmsg: adt {
+	data: array of byte;
+	datalen: int;
+	next: cyclic ref Wmsg;
+};
+
+writer(fd: ref Sys->FD, sc: chan of (int, int, Point, Point))
+{
+	lastcol := -1;
+	lastw := -1;
+	lastpt := Point(-1, -1);
+	curmsg: ref Wmsg;
+	nextmsg: ref Wmsg;
+
+	eofc := chan of int;
+	wc := chan of ref Wmsg;
+	wseof := 0;
+	spawn wslave(fd, wc, eofc);
+
+	for (;;) {
+		colour := -1;
+		width := 0;
+		p0, p1: Point;
+
+		if (curmsg == nil || wseof)
+			(colour, width, p0, p1) = <-sc;
+		else alt {
+		wseof = <-eofc =>
+			;
+
+		(colour, width, p0, p1) = <-sc =>
+			;
+
+		wc <-= curmsg =>
+			curmsg = curmsg.next;
+			continue;
+		}
+
+		newseq := 0;
+		if (curmsg == nil) {
+			curmsg = ref Wmsg(array [Sys->ATOMICIO] of byte, 0, nil);
+			nextmsg = curmsg;
+			newseq = 1;
+		}
+
+		if (colour != lastcol || width != lastw || p0.x != lastpt.x || p0.y != lastpt.y)
+			newseq = 1;
+
+		d: array of byte = nil;
+		if (!newseq) {
+			d = sys->aprint(" %d %d", p1.x, p1.y);
+			if (nextmsg.datalen + len d >= Sys->ATOMICIO) {
+				nextmsg.next = ref Wmsg(array [Sys->ATOMICIO] of byte, 0, nil);
+				nextmsg = nextmsg.next;
+				newseq = 1;
+			}
+		}
+		if (newseq) {
+			d = sys->aprint(" %d %d %d %d %d %d", colour, width, p0.x, p0.y, p1.x, p1.y);
+			if (nextmsg.datalen != 0) {
+				nextmsg.next = ref Wmsg(array [Sys->ATOMICIO] of byte, 0, nil);
+				nextmsg = nextmsg.next;
+			}
+		}
+		nextmsg.data[nextmsg.datalen:] = d;
+		nextmsg.datalen += len d;
+		lastcol = colour;
+		lastw = width;
+		lastpt = p1;
+	}
+}
+
+wslave(fd: ref Sys->FD, wc: chan of ref Wmsg, eof: chan of int)
+{
+	for (;;) {
+		wm := <-wc;
+		n := sys->write(fd, wm.data, wm.datalen);
+		if (n != wm.datalen)
+			break;
+	}
+	eof <-= 1;
+}
+
+drawstroke(img: ref Image, offset, p0, p1: Point, pen: ref Image, width: int)
+{
+	p0 = p0.add(offset);
+	p1 = p1.add(offset);
+	img.line(p0, p1, Draw->Endsquare, Draw->Endsquare, width, pen, p0);
+}
+
+drawstrokes(img: ref Image, offset: Point, pen: ref Image, width: int, pts: array of Point)
+{
+	if (len pts < 2)
+		return;
+	p0, p1: Point;
+	p0 = pts[0].add(offset);
+	for (i := 1; i < len pts; i++) {
+		p1 = pts[i].add(offset);
+		img.line(p0, p1, Draw->Endsquare, Draw->Endsquare, width, pen, p0);
+		p0 = p1;
+	}
+}
+
+badmod(mod: string)
+{
+	sys->fprint(stderr, "cannot load %s: %r\n", mod);
+	raise "fail:bad module";
+}
+
+tkcmd(t: ref Tk->Toplevel, cmd: string): string
+{
+	s := tk->cmd(t, cmd);
+	if (s != nil && s[0] == '!') {
+		sys->fprint(stderr, "%s\n", cmd);
+		sys->fprint(stderr, "tk error: %s\n", s);
+	}
+	return s;
+}
+
+tkcmds(t: ref Tk->Toplevel, cmds: array of string)
+{
+	for (i := 0; i < len cmds; i++)
+		tkcmd(t, cmds[i]);
+}