crt-terminal

CRT terminal

Simple retro styled React-hooks-based terminal shell.

Demo page.

Features

1. Smooth printing
2. Command history
3. Loader
4. Ability lock command input
5. Typescript and React
6. Hooks-based with event queues under the hood
7. Zero additional dependencies

Installation and basic usage

The best way to use crt-terminal is to install it from npm and include it into your app.

yarn add crt-terminal

npm install crt-terminal

Then you need to import Terminal, useEventQueue (or implement your own EventQueue) and line/words helpers (or corresponding enum with IDs).

Important! For better experience Terminal should be wrapped into a fixed size container.

import React from 'react';
import { Terminal, useEventQueue, textLine, textWord, commandWord } from 'crt-terminal';

const bannerText = `
Hello world!

And not only world
`;

export default function App() {
  const eventQueue = useEventQueue();
  const { print } = eventQueue.handlers;

  return (
    <div style={{ width: '1000px', height: '600px' }}>
      <Terminal
        queue={eventQueue}
        banner={[textLine({ words: [textWord({ characters: bannerText })] })]}
        onCommand={(command) =>
          print([
            textLine({
              words: [
                textWord({ characters: 'You entered command: ' }),
                commandWord({ characters: command, prompt: '>' }),
              ],
            }),
          ])
        }
      />
    </div>
  );
}

Advanced usage and API reference

Required Props

1. queue: QueueInterface - object returned by useEventQueue, contains state and api fields;
2. (command: string) => void - function to be called every time new command is submitted;

Optional props

1. prompt?: string - prompt symbol before command input; default: >\xa0;

2. cursorSymbol?: string - cursor symbol inside command input; default: \xa0;

3. maxHistoryCommands?: number - max number of commands to be memorized in commands history; default: 10;

4. banner?: PrintableItem - message to be printed after Terminal is mounted; default: undefined.

5. loader?: Partial<LoaderConfig> - loader config, consist of:

   • slides: string[] - array of consecutive loader states; default: ['.', '..', '...'];
   • loaderSpeed: number - interval between state changes; default: 1000;

6. printer?: Partial<PrinterConfig> - printer config, consist of:

   • printerSpeed: number - interval between state changes; default: 20;
   • charactersPerTick: number - characters to print on each tick; default: 5;
   • onPrintStatusChange?: (nextPrintState: boolean) => void - callback which reports printer status (printing / not printing);

7. effects? enabling or disabling following effects:

   • scanner?: boolean - scanner line; default: true;
   • pixels?: boolean - "pixels" effect; default: true;
   • screenEffects?: boolean - screen shaking; default: true;
   • textEffects?: boolean - text glow, pulsing; default: true;

Event Queue

Event Queue is the main part of public interface through which component communicates with outer world. useEventQueue exports event creators in handlers field of returned object, namely:

1. print: (payload: PrintableItem) => void - prints a message on terminal "screen". Important! Print is async operation, so your next message will be printed as soon as the previous ones are done printing;
2. clear: () => void - clears terminal "screen" with respect to printing queue;
3. focus: () => void - focuses terminal input;
4. lock: (payload: boolean) => void - locks/unlocks terminal input preventing any user attempt to enter a command;
5. loading: (payload: boolean) => void - starts/ends loader. Important! Loading start locks input automatically, if it is not locked yet. Loading end unlocks input automatically, if it was locked by loader.

You can use these handlers everywhere to fully control behavior of your terminal.

If you don't like event creators, you can use enqueue function from api field of the object returned by useEventQueue. In this case you also need to import enums PrinterEvents and TerminalEvents. Important! To avoid possible bugs, you should pass a newly created object every time enqueue method is called.

Sentence, Sentence Helpers

As one can notice print handler prints a PrintableItem. PrintableItem or sentence is an array of Lines. Line is essentially a new div on the screen, each line has field words containing array of Words. There are two types of lines:

1. TextLine (larger x-padding, no y-padding)
2. CommandLine (smaller x-padding, has y-padding).

Important! Each Lines and Words have common optional fields:

1. data-crt-terminal - can be defined for customization, better search, etc.
2. className
3. id

Word is essentially a new span inside a line. Word can be multilined. Each word has characters filed containing content of a word. There are following types of words:

1. AnchorWord - <a> element with optional href and onClick fields
2. TextWord - <span> element
3. ButtonWord - <button> element with optional onClick field
4. CommandWord - <span> element with required prompt field

There are two ways of creating Lines and Words:

1. Using helper functions textWord, buttonWord, commandWord, anchorWord, commandLine, textLine
2. Using object literals, in this cases you need to import WordTypes, LineTypes enums

Styling

Every element inside terminal has special fixed style, to which you can safely refer to. You can also add your own className for lines and words.

Command history

Command history saves entered commands, but no more then maxHistoryCommands. You can get previous/next saved command by pressing Arrow Up / Arrow Down

Repo

It is a turborepo-based monorepo set up for testing and developing. Library itself is inside packages/crt-terminal, demo app is inside apps/web; to start locally just yarn dev in root folder.

License

MIT Licensed. Copyright (c) Dmitriy Lipin 2022.