
 ZVT - Zed's Virtual Terminal
 Copyright (C) Michael Zucchi, 1998
 
Notes
-----

This is a quick read-me to cover this work-in-progress release
of 'zterm' - "yet another virtual terminal" program.

My original goal was to write a small-as-possible, fast and
efficient X term type program, which would also provide equivalent
functionality (if not semantically identical).  Some of the
extra features may bloat this a little, and X itself bloats
it a lot (especially at run-time :(  but it should still
come in pretty light-weight (currently the stripped binary
is under 40K!  It also seems to benchmark with extrememly low
CPU times on large amounts of scrolling/screen output).

One thing I've tried to do was detach the 'vt' terminal emulation
code from the rendering code.  Something similar to Curses.
But I've used a rotating linked list 'buffer' to emulate
scrolling and other functions, so it actually runs
very fast.  It reads as much data as the terminal client
wants to send, processes it all in the off screen buffer, and
then renders this onto the screen.  It also uses some of the
characteristics of the off-screen buffer to try to optimize
the on-screen update as well (using scrolling where possible
for example).  It has also been completely written from
scratch, so does not have any hang-overs from old code
(although no doubt it has its own plethora of bugs).

Sometimes it seems to over-generate X traffic (by trying to optimize
line updates to small segments), but on the whole it seems to work
pretty well.

On top of the base terminal emulation, it has the usual select/paste,
font setting, and so on.

The base vt emulation library has been used to implement
a new gtk widget 'ZvtTerm'.  Refer to zterm.c for a simple
example of using this widget.

Installation
------------

Since this is now part of the Gnome CVS tree, refer to
the gnome-libs building instructions.

A simple test client 'zterm' which is not installed by
default is compiled in this directory.

Command line arguments
----------------------

There are currently some rudimentary command-line arguments
to zterm which can be used to control its behavior.

 -e command [ args ... ]

Execute command 'command', passing it the remainder of the command
line (i.e. the -e command must be the last one on the command line).
This behaves identical to the Xterm -e command.

 -s <number>

Set the scrollback lines to <number>.  This is the number of lines
stored in the scrollback buffer.

Current Features
----------------

 Xterm emulation.  Should use the Xterm or Xterm_colour termcap for
the zvtterm widget.  However, not all X term stuff is in there (like
setting the title, for example), and not all the vt100 stuff is there
either (like reporting terminal type).  I've crashed it dumping a huge
binary file to it, but most of the core vt100 escape sequences are
implemented.  (all the curses programs I have seem to work as
expected - emacs/vi/mc).

 Mouse blanking.  The Amiga has a neat little commodity (hmm, perhaps
a Gnome window manager or Panel could include something like
commodities? ...) which would blank the mouse when a key was pressed,
and un-blank it when the mouse was moved.  Anyway, zvt does this
too because I think its neat.

 Blinking cursor.  Yeah kinda wanky, but it is nice to have.

 Selection and pasting.  These work as expected.  The selection
works almost, but not quite like the Xterm selection algorithm.
Actually it tries to be a little smarter - tabs should be able
to be selected/pasted too.  Still a few bugs with selection end-points
and the rendering of selections.  The widget doesn't follow the
pointer for one.

 Scroll-back buffer.  Again, works as you'd expect.  Currently
no optimization is done on the re-rendering of a scroll-back
'scroll', but it works OK on fast machines.  The zterm example
program doesn't set one up, but the widget keeps track of
scrolled lines.

 Jump scroll.  After I saw gemvt in action I immediately thought
"this needs jump scroll", but I didn't see how it could be done
with the code as it stood (being based on the Linux VC code it
was designed to work directly on the display medium).  So I began
to experiment with a vt emulator based on optimized off-screen
buffer -> on-screen display update - and this is what I came up with.
Anyway, the result is a very fast, very responsive terminal that
will still generate an accurate screen and scroll-back buffer.

Licensing
---------

 zterm, and the zvtterm widget is Free Software, and has been
released under the GNU LGPL.  

 Refer to the file "COPYING" accompanying this file.

Known Bugs
----------

 Refer to the file "BUGS" accompanying this file.
 Also see the file "TODO" for other information.

Contacting the Author
---------------------

I can be reached at: zucchi@zedzone.mmc.com.au

Bug reports/ideas welcome.

Since I work full time (system designer/developer/systems administrator),
and my gf gets annoyed when I spend so much time doing
this kinda stuff, updates may take a while :)

Zed was my 'coding handle' on the Amiga, hence the name 'zterm', and
'zvtterm widget'.

