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The Minitel emulator

The MiEdit project comes with a Minitel Emulator which can be used independantly provided that you can write some lines of code.

HTML code

The Minitel emulator does not create visible elements on your page, they must already exist or dynamically created (this option won't be discussed here).

The following code is needed to have a Minitel emulator with keyboard and cursor functionalities:

<x-minitel data-socket="ws://mntl.joher.com:2018/?echo"
           data-speed="0"
           data-color="true">
    <canvas data-minitel="screen"></canvas>
    <canvas data-minitel="cursor"></canvas>

    <import src="import/minitel-keyboard.html"></import>

    <audio data-minitel="beep">
        <source src="sound/minitel-bip.mp3" type="audio/mpeg"/>
        Too bad, your browser does not support HTML5 audio or mp3 format.
    </audio>      
</x-minitel>

The x-minitel tag

The x-minitel tag is a custom tag container for one Minitel emulator. You can have as many x-minitel tag as you want on a page.

The only mandatory element it must contain is a canvas with the data-minitel attribute set to screen. The emulator won’t complain if a keyboard or cursor are missing from the container.

The x-minitel tag supports these custom attributes:

  • data-socket, a web socket to which the emulator will connect. If it is missing, you will have to directly feed the emulator using its send method.
  • data-speed, the speed the emulator should use, it can be either 0, 1200, 4800 or 9600. 1200 is the standard Minitel speed, 4800 was used by administrators on local Minitel, 9600 was used by the photographic Minitels. 0 means the emulator will run as fast as your computer/browser/network will allow.
  • data-color, true to use colors, false to use grayscales.

The speed and color settings can be dynamically set later by program.

The canvas data-minitel="screen" tag

This is the only mandatory element and should be the first.

It will be used by the emulator to draw the image on.

The canvas data-minitel="cursor" tag

This is an optional element.

It will be used by the emulator to draw a blinking cursor on when the Videotex stream requires it.

It is the responsibility of the CSS stylesheet to place this canvas above the screen canvas to achieve the desired result. It should also ignore pointer events:

canvas[data-minitel="cursor"] {
    position: absolute;
    top: 0;
    left: 0;
    pointer-events: none;
}

The div data-minitel="keyboard" tag

This is an optional element.

It will be used by the emulator to display a virtual keyboard and handles key strokes.

A standard Minitel keyboard is available in import/minitel-keyboard.html.

You can write and style your own keyboard but each key must have the data-call and data-param set accordingly to the standard Minitel keyboard, otherwise the emulator won’t be able to receive key clicks.

The audio data-minitel="beep" tag

This is an optional element.

It will be used by the emulator to emit a beep sound when then Videotex stream requires it.

You can use any sound you like instead of the standard one.

Running the Minitel emulator

Required files

The following files are required in order for the emulator to work:

  • library/generichelper/generichelper.js, some unrelated functions to make programming easier.
  • library/import-html/import-html.js, handles any import tag (used in the example to import the keyboard HTML code).
  • library/autocallback/autocallback.js, associates data-call and data-param to their correspond handlers.
  • library/query-parameters/query-parameters.js, read parameters from the query string.
  • library/finite-stack/finite-stack.js, a finite stack that never overflows.
  • library/key-simulator/key-simulator.js, simulates the sound a keyboard key makes when used.
  • library/settings-suite/settings-suite.js, handles settings given through various ways (query parameters, data attribute, function argument or default value).
  • library/minitel/constant.js, every Minitel constants are here. And the automaton too.
  • library/minitel/protocol.js, the Videotex stream decoder.
  • library/minitel/elements.js, an helper class to retrieve elements of the Minitel emulator from the DOM.
  • library/minitel/text-grid.js, handles text grid dimensions.
  • library/minitel/char-size.js, handles character size in pixels.
  • library/minitel/font-sprite.js, load and draw sprite fonts.
  • library/minitel/page-cell.js, a Videotex cell in the video RAM.
  • library/minitel/vram.js, the video RAM.
  • library/minitel/vdu-cursor.js, the blinking cursor.
  • library/minitel/vdu.js, the visual display unit which controls video RAM and blinking cursor.
  • library/minitel/decoder.js, the "boss" which knows what to do with the Videotex stream.
  • library/minitel/keyboard.js, the keyboard.
  • library/minitel/minitel-emulator.js, the emulator itself which will connect every part to each other.
  • library/minitel/start-emulators.js, an helper function instanciating a Minitel.Emulator object for each x-minitel tag found in the DOM.

These files should be imported in this order.

They can be concatenated and minified in order to save bandwidth.

Start the emulator

The Minitel emulator is run by instanciating the Minitel.Emulator class.

The emulator comes with a startEmulators helper function.

Running every emulator present on a page is as simple as:

const emulators = Minitel.startEmulators()

This works well when settings are defined as x-minitel attributes.

If you want to specify settings other way, you will have to directly use the Minitel.Emulator class, which is not that difficult to do.

Specifying settings

Settings can be specified multiple ways. The priority order is the following:

  • query parameters,
  • function argument,
  • data-* attribute,
  • default value.

Classes

A Minitel emulator instance is mainly composed of the following classes:

Minitel emulator classes