Ecosyste.ms: Awesome

An open API service indexing awesome lists of open source software.

Awesome Lists | Featured Topics | Projects

https://github.com/propensive/yossarian

The insanity of terminal emulation
https://github.com/propensive/yossarian

ansi-escapes console console-emulator headless pty scala terminal-emulation terminal-emulator tty

Last synced: 25 days ago
JSON representation

The insanity of terminal emulation

Awesome Lists containing this project

README 

        
[GitHub Workflow](https://github.com/propensive/yossarian/actions)

[](https://discord.gg/7b6mpF6Qcf)




# Yossarian



__The insanity of terminal emulation__



_Yossarian_ is a headless terminal emulator. It receives input, as a stream of

bytes, and interprets it to maintain the state of a terminal, of some size. In

particular, most standard any many common escape sequences will be interpreted

to modify the terminal's content (including colors and styles), cursor

position, and hyperlinks.



## Features



- interprets ANSI control sequences, notably CSI and SGR codes

- terminals of any dimensions can be emulated

- the graphic rendition of each character cell is tracked independently

- hyperlinks are also tracked for each cell

- take snapshots of the terminal



## Availability Plan



Yossarian has not yet been published. The medium-term plan is to build Yossarian

with [Fury](https://github.com/propensive/fury) and to publish it as a source build on

[Vent](https://github.com/propensive/vent). This will enable ordinary users to write and build

software which depends on Yossarian.



Subsequently, Yossarian will also be made available as a binary in the Maven

Central repository. This will enable users of other build tools to use it.



For the overeager, curious and impatient, see [building](#building).



## Getting Started



All terms and types are defined in the `yossarian` package:

```scala

import yossarian.*

```



### Create a new Pseudo-Terminal



An instance of `Pty`, representing a pseudo-terminal (PTY), is the main

entry-point to Yossarian's features. We can create one by specifying its width

and height:

```scala

val pty = Pty(80, 24)

```



This represents a screen size of 80×24 characters, white-on-black text, with a

cursor in the top-left corner, and no interesting text styles.



### Updating PTY state



Input may be provided to the `Pty` instance by supplying it as a `Text` value

to the `consume` method. For example,

```scala

val pty2 = pty.consume(t"Hello world\n")

```



This will construct a new `Pty` with the words `Hello world` on its virtual

screen, and move the cursor to the start of the next line. This is an immutable

operation, so the original state of `pty` will be unchanged.



### Accessing PTY state



Changing the state of the PTY is not useful unless we can inspect its state! We

can access much of that state through `pty.buffer`, and instance of

`ScreenBuffer`.



A `ScreenBuffer` represents a rectangular region of characters in the

pseudo-terminal, which may not be the entire terminal window, and provides the

following methods:

 - `width` and `height`, to get the buffer's dimensions

 - `char(x, y)`, to get the character at a particular position

 - `style(x, y)`, to get the `Style` instance for a position

 - `link(x, y)`, to get the link text applied to the position

 - `line`, to get a new `ScreenBuffer` of the entire screen as a single line

 - `render`, to get the textual content of the screen

 - `styles`, to get an array of the `Style`s for each character in the buffer

 - `find(text)`, to get a smaller `ScreenBuffer` whose content matches the

   search text



A `Style` value provides information on the visual style of a single character

in a `ScreenBuffer`. It includes the properties, `bold`, `italic`, `blink`

(blinking text), `faint`, `conceal` (invisible text), `strike`

(strike-through), `underline`, `reverse` (inverted colors), `foreground`

(color) and `background` (color).



#### Interactivity



A pseudoterminal sometimes needs to _produce_ output to communicate with the

process controlling it. For example, if the PTY receives the escape codes to

query its size, it needs to respond through some channel.



The `stream` method of `Pty` will provide a stream of `Text` output from the

pseudo-terminal, which the controlling process and read and interpret

accordingly.



## Status



Yossarian is classified as __embryotic__. For reference, Soundness projects are

categorized into one of the following five stability levels:



- _embryonic_: for experimental or demonstrative purposes only, without any guarantees of longevity

- _fledgling_: of proven utility, seeking contributions, but liable to significant redesigns

- _maturescent_: major design decisions broady settled, seeking probatory adoption and refinement

- _dependable_: production-ready, subject to controlled ongoing maintenance and enhancement; tagged as version `1.0.0` or later

- _adamantine_: proven, reliable and production-ready, with no further breaking changes ever anticipated



Projects at any stability level, even _embryonic_ projects, can still be used,

as long as caution is taken to avoid a mismatch between the project's stability

level and the required stability and maintainability of your own project.



Yossarian is designed to be _small_. Its entire source code currently consists

of 441 lines of code.



## Building



Yossarian will ultimately be built by Fury, when it is published. In the

meantime, two possibilities are offered, however they are acknowledged to be

fragile, inadequately tested, and unsuitable for anything more than

experimentation. They are provided only for the necessity of providing _some_

answer to the question, "how can I try Yossarian?".



1. *Copy the sources into your own project*

   

   Read the `fury` file in the repository root to understand Yossarian's build

   structure, dependencies and source location; the file format should be short

   and quite intuitive. Copy the sources into a source directory in your own

   project, then repeat (recursively) for each of the dependencies.



   The sources are compiled against the latest nightly release of Scala 3.

   There should be no problem to compile the project together with all of its

   dependencies in a single compilation.



2. *Build with [Wrath](https://github.com/propensive/wrath/)*



   Wrath is a bootstrapping script for building Yossarian and other projects in

   the absence of a fully-featured build tool. It is designed to read the `fury`

   file in the project directory, and produce a collection of JAR files which can

   be added to a classpath, by compiling the project and all of its dependencies,

   including the Scala compiler itself.

   

   Download the latest version of

   [`wrath`](https://github.com/propensive/wrath/releases/latest), make it

   executable, and add it to your path, for example by copying it to

   `/usr/local/bin/`.



   Clone this repository inside an empty directory, so that the build can

   safely make clones of repositories it depends on as _peers_ of `yossarian`.

   Run `wrath -F` in the repository root. This will download and compile the

   latest version of Scala, as well as all of Yossarian's dependencies.



   If the build was successful, the compiled JAR files can be found in the

   `.wrath/dist` directory.



## Contributing



Contributors to Yossarian are welcome and encouraged. New contributors may like

to look for issues marked

[beginner](https://github.com/propensive/yossarian/labels/beginner).



We suggest that all contributors read the [Contributing

Guide](/contributing.md) to make the process of contributing to Yossarian

easier.



Please __do not__ contact project maintainers privately with questions unless

there is a good reason to keep them private. While it can be tempting to

repsond to such questions, private answers cannot be shared with a wider

audience, and it can result in duplication of effort.



## Author



Yossarian was designed and developed by Jon Pretty, and commercial support and

training on all aspects of Scala 3 is available from [Propensive

OÜ](https://propensive.com/).



## Name



_Yossarian_ was the protagonist in Joseph Heller's _Catch 22_, in which he desires to be declared _insane_ in order to be excused from flying combat missions. But in doing so, he must request an evaluation, which only a _sane_ person would do, and would thus be considered proof of sanity. This library makes it possible to evaluate the sanity of terminal output.



In general, Soundness project names are always chosen with some rationale,

however it is usually frivolous. Each name is chosen for more for its

_uniqueness_ and _intrigue_ than its concision or catchiness, and there is no

bias towards names with positive or "nice" meanings—since many of the libraries

perform some quite unpleasant tasks.



Names should be English words, though many are obscure or archaic, and it

should be noted how willingly English adopts foreign words. Names are generally

of Greek or Latin origin, and have often arrived in English via a romance

language.



## Logo



The logo shows an abstract depiction of some rows of content in a console.



## License



Yossarian is copyright © 2024 Jon Pretty & Propensive OÜ, and

is made available under the [Apache 2.0 License](/license.md).