Modern line-oriented terminal emulator without support for TUIs.
Mainstream terminal emulators (urxvt, xterm, alacritty, …) support a standard known as ANSI escape sequences. 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 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 is largely incompatible with fixed-size columns. For this reason, terminal emulator supporting the aforementioned escape sequences can never fully support Unicode [1].
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-keybindings) can be implemented directly in the
terminal emulator.
Silly, buggy, and incomplete prototype implementation.
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, …)
- Basic support for SGR escape sequences (colors, font modifiers, …)
This software has the following dependencies:
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.
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 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
The terminal appearance can be configured using Gtk's 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.
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) or network protocols tunneled over SSH connections (e.g. 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 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.
This work is heavily inspired by the Plan 9 terminal emulator, usage of
which is further described in the rio(1) man page.
This terminal emulator was also ported to Unix as part
of plan9port. An (unmaintained) reimplementation using
Ruby and the Tk GUI toolkit, named tt, is also available.
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/
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/.