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