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var CanvasRenderer = function(el, options) { |
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var cachedBackground; |
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var canvas = document.createElement('canvas'); |
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el.appendChild(canvas); |
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if (typeof(G_vmlCanvasManager) !== 'undefined') { |
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G_vmlCanvasManager.initElement(canvas); |
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} |
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var ctx = canvas.getContext('2d'); |
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canvas.width = canvas.height = options.size; |
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var scaleBy = 1; |
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if (window.devicePixelRatio > 1) { |
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scaleBy = window.devicePixelRatio; |
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canvas.style.width = canvas.style.height = [options.size, 'px'].join(''); |
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canvas.width = canvas.height = options.size * scaleBy; |
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ctx.scale(scaleBy, scaleBy); |
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} |
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ctx.translate(options.size / 2, options.size / 2); |
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ctx.rotate((-1 / 2 + options.rotate / 180) * Math.PI); |
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var radius = (options.size - options.lineWidth) / 2; |
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if (options.scaleColor && options.scaleLength) { |
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radius -= options.scaleLength + 2; |
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} |
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Date.now = Date.now || function() { |
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return +(new Date()); |
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}; |
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var drawCircle = function(color, lineWidth, percent) { |
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percent = Math.min(Math.max(-1, percent || 0), 1); |
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var isNegative = percent <= 0 ? true : false; |
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ctx.beginPath(); |
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ctx.arc(0, 0, radius, 0, Math.PI * 2 * percent, isNegative); |
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ctx.strokeStyle = color; |
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ctx.lineWidth = lineWidth; |
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ctx.stroke(); |
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}; |
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var drawScale = function() { |
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var offset; |
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var length; |
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ctx.lineWidth = 1; |
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ctx.fillStyle = options.scaleColor; |
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ctx.save(); |
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for (var i = 24; i > 0; --i) { |
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if (i % 6 === 0) { |
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length = options.scaleLength; |
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offset = 0; |
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} else { |
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length = options.scaleLength * 0.6; |
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offset = options.scaleLength - length; |
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} |
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ctx.fillRect(-options.size/2 + offset, 0, length, 1); |
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ctx.rotate(Math.PI / 12); |
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} |
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ctx.restore(); |
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}; |
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var reqAnimationFrame = (function() { |
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return window.requestAnimationFrame || |
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window.webkitRequestAnimationFrame || |
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window.mozRequestAnimationFrame || |
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function(callback) { |
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window.setTimeout(callback, 1000 / 60); |
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}; |
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}()); |
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var drawBackground = function() { |
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if(options.scaleColor) drawScale(); |
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if(options.trackColor) drawCircle(options.trackColor, options.trackWidth || options.lineWidth, 1); |
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}; |
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this.getCanvas = function() { |
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return canvas; |
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}; |
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this.getCtx = function() { |
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return ctx; |
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}; |
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this.clear = function() { |
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ctx.clearRect(options.size / -2, options.size / -2, options.size, options.size); |
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}; |
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this.draw = function(percent) { |
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if (!!options.scaleColor || !!options.trackColor) { |
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if (ctx.getImageData && ctx.putImageData) { |
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if (!cachedBackground) { |
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drawBackground(); |
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cachedBackground = ctx.getImageData(0, 0, options.size * scaleBy, options.size * scaleBy); |
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} else { |
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ctx.putImageData(cachedBackground, 0, 0); |
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} |
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} else { |
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this.clear(); |
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drawBackground(); |
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} |
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} else { |
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this.clear(); |
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} |
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ctx.lineCap = options.lineCap; |
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var color; |
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if (typeof(options.barColor) === 'function') { |
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color = options.barColor(percent); |
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} else { |
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color = options.barColor; |
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} |
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drawCircle(color, options.lineWidth, percent / 100); |
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}.bind(this); |
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this.animate = function(from, to) { |
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var startTime = Date.now(); |
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options.onStart(from, to); |
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var animation = function() { |
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var process = Math.min(Date.now() - startTime, options.animate.duration); |
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var currentValue = options.easing(this, process, from, to - from, options.animate.duration); |
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this.draw(currentValue); |
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options.onStep(from, to, currentValue); |
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if (process >= options.animate.duration) { |
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options.onStop(from, to); |
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} else { |
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reqAnimationFrame(animation); |
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} |
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}.bind(this); |
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reqAnimationFrame(animation); |
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}.bind(this); |
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}; |
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