This
[http://www.engcorp.com/acf/terminal%20emulator]
page has a few general remarks on the role of terminal emulators.
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Ian Bell's "8052 Development for [Linux] Users"
[http://www.8052.com/users/redtommo/] and 
[Melissa Schrumpf]'s post 
[http://groups-beta.google.com/group/comp.lang.tcl/browse_thread/thread/766404abca996fdc]
on automation of 
miscellaneous devices both illustrate how experienced
developers think about terminal emulation.
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[[Describe rxvt and the one Don distributes with [Expect].]]

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I've seen the expect example, and it works amazingly well. What I would like to know is whether or not it's possible to get the same effect with pure [tcl/tk]. The acid test would be to run [vi] within a [tk]-based emulator without  using the expect extension.

[RJM] Hm. Don't know exactly what you mean. But for the sake of this pages' title an example of an extremely simple terminal emulator follows here. You can adapt/extend it for your own purpose.
 set serial [open com1 r+]
 fconfigure $serial -mode "9600,n,8,1" -blocking 0 -buffering none -translation binary
 fileevent $serial readable {.t insert end [read $serial]}
 pack [text .t]
 bind .t <KeyPress> {puts -nonewline $serial %A; break}
The ''break'' prevents local echo of typed characters on the text widget.

''Exactly what I mean: I want to [exec] vi and have its input and output managed through a tk [widget]. It has nothing to do with a serial communications port.''
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[DL] I think the answer to the original question may have different answers depending on whether you're on a [UNIX]-based platform (which would include [MacOS]) or a [Windows] platform.  On UNIX, you need [pseudotty]s, something vanilla Tcl just doesn't provide support for - except with the Expect [extension].  On Windows, there is no unified mechanism for interacting with other programs.  The simple script above merely opens a connection to a serial port.  If your idea of a terminal emulator is to interact with a serial port, then yes you can get by with a pure Tcl script.


The [Expect] terminal emulator is pretty full-featured.  It supports/understands:
   * scrollbars
   * both termcap and terminfo
   * meta-key (so things like zsh, emacs, etc work)
   * selections
   * standout mode, function keys, etc, etc, etc.

Plus, it supports screen-scraping.

If you want to understand it in detail, the [BOOK Exploring Expect] has a code walk-through of the terminal emulator.


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See also [A simple serial terminal]



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[Category Glossary]