From mboxrd@z Thu Jan  1 00:00:00 1970
To: 9fans@cse.psu.edu
Subject: Re: [9fans] Limbo Tk FAQ?
From: rog@vitanuova.com
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Date: Fri, 25 May 2001 13:10:55 +0100
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> Tcl with channels would do well, too :-)  (Oops, I hope I'm not
> speaking through my nose here, I've only given the code a brief
> glimpse, looking forward to look at it in more detail later).

i added a loadable module for the inferno shell to give shell access to
tk; this also includes channels (as they're an inextricable part of the
inferno tk interface).

some will turn up their noses, but i've found it quite nice for
knocking up simple graphical demo scripts written in shell script. part
of the reason is that the shell is multi-process, so channels sit quite
nicely with it.

	load tk
	wid := ${tk window 'Test window'}
	while {} {
		tk winctl $wid ${recv $wid}
	} &

the first line loads the tk module; the second creates a new tk window,
and returns an identifier for it, which is also the name of a channel
on which window events can be received. the third starts a background
process looping forever receiving from the channel and processing the
event that it got.

the only part not familiar from rc is the ${...} notation which yields
the result of a loadable-module-defined command (sort of like `{...}
but without the uncertainty of the usual stdout tokenization)

once you've defined a function to execute tk commands:

	fn x {
		tk $wid $*
	}

one can execute tk commands quite simply:

	x button .b -text {Hello world} -command {send cmd hello, world}
	x pack .b
	x update
	chan cmd
	tk namechan $wid cmd
	while {} {
		echo ${recv cmd}
	}

i guess this feels somewhat like tcl; it's certainly nice for hacking
up simple graphical interfaces to shell commands.