A high-performance JavaScript danmaku engine. 高性能弹幕引擎库
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README.md

Danmaku

Build status Coverage Dependencies NPM version License File size jsDelivr

Browser compatibility

Danmaku is a JavaScript library to display flying comments on HTML5 video. It can also display comments to your container in real time without timeline or be used with HTML5 audio.

Demo

中文文档

Installation

You can install it by using npm or bower:

npm install danmaku
bower install danmaku

You can also use jsDelivr CDN or download danmaku.min.js directly.

Usage

Video mode

<video id="my-video" src="./example.mp4"></video>

<script src="./dist/danmaku.min.js"></script>
<script>
  var danmaku = new Danmaku();
  danmaku.init({
    video: document.getElementById('my-video'),
    comments: []
  });
</script>

Audio mode

<div id="my-container" style="width:640px;height:360px;"></div>
<audio id="my-audio" src="./example.mp3"></audio>

<script src="./dist/danmaku.min.js"></script>
<script>
  var danmaku = new Danmaku();
  danmaku.init({
    container: document.getElementById('my-container'),
    audio: document.getElementById('my-audio'),
    comments: []
  });
</script>

Live mode

To display comments in real time, you need to set up server and use something like Socket.IO. Danmaku is just receiving comments data and display them to container.

Here is a simple example using with Socket.IO and Node.js.

Server:

const app = require('http').createServer(handler);
const io = require('socket.io')(app);
app.listen(80);
function handler(req, res) {
  // your handler...
}
io.on('connection', socket => {
  socket.on('danmaku', comment => {
    socket.broadcast.emit('danmaku', comment);
  });
});

Client:

<div id="my-container" style="width:640px;height:360px;"></div>
<button id="send-button">Send</button>

<script src="./socket.io.js"></script>
<script src="./dist/danmaku.min.js"></script>
<script>
  var danmaku = new Danmaku();
  danmaku.init({
    container: document.getElementById('my-container')
  });
  var socket = io();
  socket.on('danmaku', function(comment) {
    danmaku.emit(comment)
  });
  var btn = document.getElementById('send-button');
  btn.addEventListener('click', function() {
    var comment = {
      text: 'bla bla',
      style: {
        fontSize: '20px',
        color: '#ffffff'
      },
    };
    danmaku.emit(comment);
    socket.emit('danmaku', comment);
  });
</script>

API

Initialization

var danmaku = new Danmaku();
danmaku.init({
  // The stage to display comments will be appended to container.
  container: document.getElementById('my-container'),

  // Danmaku will create a container automatically and append video to the
  // container if container isn't assigned.
  video: document.getElementById('my-video'),

  // You should always assign a container when using audio mode.
  audio: document.getElementById('my-audio'),

  // Array of comment, you can find its format in `danmaku.emit` API.
  comments: [],

  // You can use 'DOM' engine or 'canvas' engine to render comments.
  // Canvas engine may more efficient than DOM however it costs more memory.
  // 'DOM' by default, available in all mode.
  engine: 'canvas',

  // You can also set speed by using `danmaku.speed` API.
  speed: 144
});

Or just put options here:

var danmaku = new Danmaku({/* options */});

Emit a comment

danmaku.emit({
  text: 'example',

  // When using DOM engine, `text` can be parsed as HTML if `html` is `true`.
  // You should never pass in users' inputs directly to avoid XSS.
  // `false` by default.
  // DEPRECATED, use `render` instead.
  html: false,

  // 'rtl'(right to left) by default, available mode: 'ltr', 'rtl', 'top', 'bottom'.
  mode: 'rtl',

  // Specified in seconds, if not provided when using with media(video or audio),
  // it will be set to `media.currentTime`. Not required in live mode.
  time: 233.3,

  // When using DOM engine, Danmaku will create a <div> node for each comment,
  // these styles will be set to `node.style` directly, just write with CSS rules.
  style: {
    fontSize: '20px',
    color: '#ffffff',
    border: '1px solid #337ab7',
    textShadow: '-1px -1px #000, -1px 1px #000, 1px -1px #000, 1px 1px #000'
  },

  // When using canvas engine, following properties are available by default
  // as a CanvasRenderingContext2D object.
  canvasStyle: {
    // In Chrome, minimum font-size is 12px
    font: '10px sans-serif',
    textAlign: 'start',
    // Note that 'bottom' is the default
    textBaseline: 'bottom',
    direction: 'inherit',
    fillStyle: '#000',
    // If strokeStyle isn't assigned, there will be no stroke.
    strokeStyle: '#000',
    // It will be effect like strokeWidth.
    lineWidth: 1.0,
    shadowBlur: 0,
    shadowColor: '#000',
    shadowOffsetX: 0,
    shadowOffsetY: 0,
    filter: 'none',
    globalAlpha: 1.0
  },

  // A custom render to draw your comment.
  // when `render` exist, `text`, `html`, `style` and `canvasStyle` will be ignored.

  // When using DOM engine, you should return an HTMLElement.
  render: function() {
    var $div = document.createElement('div');
    var $img = document.createElement('img');
    $img.src = '/path/to/xxx.png';
    $div.appendChild($img);
    return $div;
  },
  // When using canvas engine, you should return an HTMLCanvasElement.
  render: function() {
    var canvas = document.createElement('canvas');
    canvas.width = 320;
    canvas.height = 180;
    var ctx = canvas.getContext('2d');
    ctx.beginPath();
    ctx.arc(75, 75, 50, 0, 2 * Math.PI);
    ctx.stroke();
    return canvas;
  }
});

More details about CanvasRenderingContext2D.

Tips:

  • With DOM engine, you may want to change line spacing by set line-height to each comment, a better way is set line-height to the container.
  • With canvas engine, line height is 1.2 by default, you can set it with canvasStyle.font.
  • canvasStyle.font uses the same syntax as the CSS font specifier. However you can only use px, %, em, rem units, I'm sure you don't need others.
  • There is a hitbox for each comment, which height is determined by its line height. When canvasStyle.textBaseline is top or hanging, the baseline is set to top of the hitbox; when it's middle, baseline is middle of the hitbox; otherwise baseline is bottom of the hitbox. So if you set canvasStyle.textBaseline to alphabetic or hanging, the comment's head or foot may out of the hitbox and be invisible.
  • canvasStyle.filter is supported in Chrome 52 and Firefox 49.

Resize

Do it when you resize container or video.

danmaku.resize();

Show

danmaku.show();

Hide

If you set display: none; to the container directly when using DOM engine, you should also do danmaku.hide() otherwise the typesetting will be broken when it's showed.

danmaku.hide();

Clear

Clear current stage.

danmaku.clear();

Speed

There is a property duration for all comments, which means how long will a comment be shown to the stage. duration is calculated by stage.width / danmaku.speed, and danmaku.speed is a standard for all comments, because the actually speed for each comment is then calculated by (comment.width + stage.width) / duration. The default value is 144.

danmaku.speed = 144;

Destroy

Destroy danmaku instance and release memory.

danmaku.destroy();