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# saneterm
Modern line-oriented terminal emulator without support for TUIs.
## Motivation
Mainstream terminal emulators (urxvt, xterm, alacritty, …) support a
standard known as [ANSI escape sequences][wikipedia ansi]. This standard
defines several byte sequences to provide special control
functions for terminals emulators. This includes control of the cursor,
support for different colors, et cetera. They are often used to
implement TUIs, e.g. using the [ncurses][ncurses web] library.
Many of these escape sequences operate on rows and columns and therefore
require terminal emulators to be built around a character grid were
individual cells can be modified. Historically, this was very useful to
implement UIs on physical terminals like the VT100. Nowadays this
approach feels dated and causes a variety of problems. For instance, the
concept of grapheme cluster as used in [Unicode][unicode web] is largely
incompatible with fixed-size columns. For this reason, terminal
emulator supporting the aforementioned escape sequences can never fully
support Unicode [\[1\]][variable-width glyphs].
On the other hand, a terminal emulator not supporting ANSI escape
sequences can never support existing TUIs. However, the idea behind
`saneterm` is that terminals shouldn't be used to implement TUIs anyhow,
instead they should focus on line-based CLIs. By doing so, a variety of
features normally implemented in CLI programs themselves (like
[readline][readline web]-keybindings) can be implemented directly in the
terminal emulator.
## Status
Silly, buggy, and incomplete prototype implementation.
## Features
By focusing on line-based input in the terminal emulator a variety of
things can be simplified and improved. `saneterm` is presently just a
prototype and provides basic implementations of the following features:
* Full Unicode support
* Support for readline-like line editing keybindings
* Editing history support directly in the terminal emulator
* File name completions
* Pager-like text handling (scrolling, searching, …)
## Installation
This software has the following dependencies:
* [python3][python web]
* [PyGObject][PyGObject web] and [gtk+3.0][gtk web]
* [setuptools][setuptools web]
If these are installed run the following command to install `saneterm`:
$ python3 setup.py install --optimize=1
You can also run saneterm's tests (with limited coverage at the moment):
$ python3 tests.py
For development setups just run `python3 -msaneterm`.
## Usage
Since many modern day shells use ANSI escape sequences heavily for
providing editing features, your favorite shell might not directly work
with `saneterm`. Simple shells like [dash][dash web] are known to work
well though. You might also want to consider using a clean environment,
to do so run the following command to start `saneterm`:
$ saneterm -- env -i dash
## Configuration
The terminal appearance can be configured using [Gtk's CSS][gtk css]
feature. The `saneterm` window widget can be selected using the CSS
selector `#saneterm`.
For example, to change the color scheme and employed font. Add the
following to your `gtk.css` configuration file located at
`$XDG_CONFIG_HOME/gtk-3.0/gtk.css`:
#saneterm textview {
font-family: Terminus;
font-size: 16px;
}
#saneterm textview text {
background-color: #181818;
color: #d8d8d8;
/* change cursor color too */
caret-color: #d8d8d8;
}
Keybindings can be configured using the same mechanism, see `keys.py`
for the default keybindings.
## FAQ
**Q:** How do I edit text on remote machines over SSH if my terminal
emulator doesn't support visual editors?
**A:** This is an interesting problem since a lot of software
relies on TUIs to be used over PTYs and SSH on remote machines. This is
mostly also an inherit flaw of Unix as it hasn't been designed with
networking and GUIs in mind. Plan 9 solves this problem through 9P file
servers, but unfortunately it has not been widely adopted and we are
stuck with Unix. In the Unix world potential solutions include
CLI-based editors (e.g. [ed][wikipedia ed]) or network protocols
tunneled over SSH connections (e.g. [Emacs Tramp Mode][emacs tramp mode]).
**Q:** How do I use pagers (e.g. `less(1)`) without support for TUIs?
**A:** With `saneterm` pagers are not needed as paging functionality is
implemented in the terminal emulator itself. For this reason, `saneterm`
offers a scrollback buffer in which autoscrolling can be configured
using the Gtk context menu. Furthermore, word wrapping can also be
disabled using the same mechanism. A search feature is also implemented
and can be activated using ctrl+f.
**Q:** How do I paste the primary clipboard when clicking the middle
mouse button?
**A:** Configure [gtk-enable-primary-paste][gtk primary paste] in
`$XDG_CONFIG_HOME/gtk-3.0/settings.ini`. Since most terminal emulator do
it this way, this may become the default in future `saneterm` versions.
**Q:** Why is this written in Python and not X?
**A:** This software is presently just a silly prototype, Python is good
for prototyping. Furthermore, Python has decent, somewhat well-documented
bindings for Gtk.
## Related Work
This work is heavily inspired by the Plan 9 terminal emulator, usage of
which is further described in the [`rio(1)`][rio man page] man page.
This terminal emulator was also [ported to Unix][9term man page] as part
of [plan9port][plan9port web].
There are also a few projects which seem to share the problem statement
outlined in the Motivation but propose different solution. Most of
which include continued support for TUIs and therefore don't benefit
from other line-based editing features. Non-complete list:
* https://github.com/withoutboats/notty
* https://github.com/christianparpart/contour
* https://notcurses.com/
## License
This program is free software: you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation, either version 3 of the License, or (at your
option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
Public License for more details.
You should have received a copy of the GNU General Public License along
with this program. If not, see <http://www.gnu.org/licenses/>.
[ncurses web]: https://invisible-island.net/ncurses/
[wikipedia ansi]: https://en.wikipedia.org/wiki/ANSI_escape_code
[wikipedia zwj]: https://en.wikipedia.org/wiki/Zero-width_joiner
[unicode web]: https://www.unicode.org/
[readline web]: https://tiswww.case.edu/php/chet/readline/rltop.html
[python web]: https://www.python.org/
[PyGObject web]: https://pygobject.readthedocs.io/en/latest/
[gtk web]: https://gtk.org/
[setuptools web]: https://pypi.python.org/pypi/setuptools
[wikipedia ed]: https://en.wikipedia.org/wiki/Ed_(text_editor)
[emacs tramp mode]: https://www.emacswiki.org/emacs/TrampMode
[variable-width glyphs]: https://gitlab.freedesktop.org/terminal-wg/specifications/-/issues/21
[rio man page]: https://9p.io/magic/man2html/1/rio
[9term man page]: https://9fans.github.io/plan9port/man/man1/9term.html
[plan9port web]: https://9fans.github.io/plan9port/
[gtk css]: https://developer.gnome.org/gtk3/stable/chap-css-overview.html
[dash web]: http://gondor.apana.org.au/~herbert/dash/
[gtk primary paste]: https://developer.gnome.org/gtk3/stable/GtkSettings.html#GtkSettings--gtk-enable-primary-paste
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