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/**
* UI component that lets the use control auto-slide
* playback via play/pause.
*/
export default class Playback {
/**
* @param {HTMLElement} container The component will append
* itself to this
* @param {function} progressCheck A method which will be
* called frequently to get the current playback progress on
* a range of 0-1
*/
constructor( container, progressCheck ) {
// Cosmetics
this.diameter = 100;
this.diameter2 = this.diameter/2;
this.thickness = 6;
// Flags if we are currently playing
this.playing = false;
// Current progress on a 0-1 range
this.progress = 0;
// Used to loop the animation smoothly
this.progressOffset = 1;
this.container = container;
this.progressCheck = progressCheck;
this.canvas = document.createElement( 'canvas' );
this.canvas.className = 'playback';
this.canvas.width = this.diameter;
this.canvas.height = this.diameter;
this.canvas.style.width = this.diameter2 + 'px';
this.canvas.style.height = this.diameter2 + 'px';
this.context = this.canvas.getContext( '2d' );
this.container.appendChild( this.canvas );
this.render();
}
setPlaying( value ) {
const wasPlaying = this.playing;
this.playing = value;
// Start repainting if we weren't already
if( !wasPlaying && this.playing ) {
this.animate();
}
else {
this.render();
}
}
animate() {
const progressBefore = this.progress;
this.progress = this.progressCheck();
// When we loop, offset the progress so that it eases
// smoothly rather than immediately resetting
if( progressBefore > 0.8 && this.progress < 0.2 ) {
this.progressOffset = this.progress;
}
this.render();
if( this.playing ) {
requestAnimationFrame( this.animate.bind( this ) );
}
}
/**
* Renders the current progress and playback state.
*/
render() {
let progress = this.playing ? this.progress : 0,
radius = ( this.diameter2 ) - this.thickness,
x = this.diameter2,
y = this.diameter2,
iconSize = 28;
// Ease towards 1
this.progressOffset += ( 1 - this.progressOffset ) * 0.1;
const endAngle = ( - Math.PI / 2 ) + ( progress * ( Math.PI * 2 ) );
const startAngle = ( - Math.PI / 2 ) + ( this.progressOffset * ( Math.PI * 2 ) );
this.context.save();
this.context.clearRect( 0, 0, this.diameter, this.diameter );
// Solid background color
this.context.beginPath();
this.context.arc( x, y, radius + 4, 0, Math.PI * 2, false );
this.context.fillStyle = 'rgba( 0, 0, 0, 0.4 )';
this.context.fill();
// Draw progress track
this.context.beginPath();
this.context.arc( x, y, radius, 0, Math.PI * 2, false );
this.context.lineWidth = this.thickness;
this.context.strokeStyle = 'rgba( 255, 255, 255, 0.2 )';
this.context.stroke();
if( this.playing ) {
// Draw progress on top of track
this.context.beginPath();
this.context.arc( x, y, radius, startAngle, endAngle, false );
this.context.lineWidth = this.thickness;
this.context.strokeStyle = '#fff';
this.context.stroke();
}
this.context.translate( x - ( iconSize / 2 ), y - ( iconSize / 2 ) );
// Draw play/pause icons
if( this.playing ) {
this.context.fillStyle = '#fff';
this.context.fillRect( 0, 0, iconSize / 2 - 4, iconSize );
this.context.fillRect( iconSize / 2 + 4, 0, iconSize / 2 - 4, iconSize );
}
else {
this.context.beginPath();
this.context.translate( 4, 0 );
this.context.moveTo( 0, 0 );
this.context.lineTo( iconSize - 4, iconSize / 2 );
this.context.lineTo( 0, iconSize );
this.context.fillStyle = '#fff';
this.context.fill();
}
this.context.restore();
}
on( type, listener ) {
this.canvas.addEventListener( type, listener, false );
}
off( type, listener ) {
this.canvas.removeEventListener( type, listener, false );
}
destroy() {
this.playing = false;
if( this.canvas.parentNode ) {
this.container.removeChild( this.canvas );
}
}
}
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