in js/reveal.js [4433:4492]
Playback.prototype.render = function() {
var progress = this.playing ? this.progress : 0,
radius = ( this.diameter / 2 ) - this.thickness,
x = this.diameter / 2,
y = this.diameter / 2,
iconSize = 14;
// Ease towards 1
this.progressOffset += ( 1 - this.progressOffset ) * 0.1;
var endAngle = ( - Math.PI / 2 ) + ( progress * ( Math.PI * 2 ) );
var 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 + 2, 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 = '#666';
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 - 2, iconSize );
this.context.fillRect( iconSize / 2 + 2, 0, iconSize / 2 - 2, iconSize );
}
else {
this.context.beginPath();
this.context.translate( 2, 0 );
this.context.moveTo( 0, 0 );
this.context.lineTo( iconSize - 2, iconSize / 2 );
this.context.lineTo( 0, iconSize );
this.context.fillStyle = '#fff';
this.context.fill();
}
this.context.restore();
};