core.scale.js

"use strict";

module.exports = function(Chart) {

	var helpers = Chart.helpers;

	Chart.defaults.scale = {
		display: true,
		position: "left",

		// grid line settings
		gridLines: {
			display: true,
			color: "rgba(0, 0, 0, 0.1)",
			lineWidth: 1,
			drawBorder: true,
			drawOnChartArea: true,
			drawTicks: true,
			tickMarkLength: 10,
			zeroLineWidth: 1,
			zeroLineColor: "rgba(0,0,0,0.25)",
			offsetGridLines: false
		},

		// scale label
		scaleLabel: {
			// actual label
			labelString: '',

			// display property
			display: false
		},

		// label settings
		ticks: {
			beginAtZero: false,
			minRotation: 0,
			maxRotation: 50,
			mirror: false,
			padding: 10,
			reverse: false,
			display: true,
			autoSkip: true,
			autoSkipPadding: 0,
			labelOffset: 0,
			callback: function(value) {
				return '' + value;
			}
		}
	};

	Chart.Scale = Chart.Element.extend({

		// These methods are ordered by lifecyle. Utilities then follow.
		// Any function defined here is inherited by all scale types.
		// Any function can be extended by the scale type

		beforeUpdate: function() {
			helpers.callCallback(this.options.beforeUpdate, [this]);
		},
		update: function(maxWidth, maxHeight, margins) {

			// Update Lifecycle - Probably don't want to ever extend or overwrite this function ;)
			this.beforeUpdate();

			// Absorb the master measurements
			this.maxWidth = maxWidth;
			this.maxHeight = maxHeight;
			this.margins = helpers.extend({
				left: 0,
				right: 0,
				top: 0,
				bottom: 0
			}, margins);

			// Dimensions
			this.beforeSetDimensions();
			this.setDimensions();
			this.afterSetDimensions();

			// Data min/max
			this.beforeDataLimits();
			this.determineDataLimits();
			this.afterDataLimits();

			// Ticks
			this.beforeBuildTicks();
			this.buildTicks();
			this.afterBuildTicks();

			this.beforeTickToLabelConversion();
			this.convertTicksToLabels();
			this.afterTickToLabelConversion();

			// Tick Rotation
			this.beforeCalculateTickRotation();
			this.calculateTickRotation();
			this.afterCalculateTickRotation();
			// Fit
			this.beforeFit();
			this.fit();
			this.afterFit();
			//
			this.afterUpdate();

			return this.minSize;

		},
		afterUpdate: function() {
			helpers.callCallback(this.options.afterUpdate, [this]);
		},

		//

		beforeSetDimensions: function() {
			helpers.callCallback(this.options.beforeSetDimensions, [this]);
		},
		setDimensions: function() {
			// Set the unconstrained dimension before label rotation
			if (this.isHorizontal()) {
				// Reset position before calculating rotation
				this.width = this.maxWidth;
				this.left = 0;
				this.right = this.width;
			} else {
				this.height = this.maxHeight;

				// Reset position before calculating rotation
				this.top = 0;
				this.bottom = this.height;
			}

			// Reset padding
			this.paddingLeft = 0;
			this.paddingTop = 0;
			this.paddingRight = 0;
			this.paddingBottom = 0;
		},
		afterSetDimensions: function() {
			helpers.callCallback(this.options.afterSetDimensions, [this]);
		},

		// Data limits
		beforeDataLimits: function() {
			helpers.callCallback(this.options.beforeDataLimits, [this]);
		},
		determineDataLimits: helpers.noop,
		afterDataLimits: function() {
			helpers.callCallback(this.options.afterDataLimits, [this]);
		},

		//
		beforeBuildTicks: function() {
			helpers.callCallback(this.options.beforeBuildTicks, [this]);
		},
		buildTicks: helpers.noop,
		afterBuildTicks: function() {
			helpers.callCallback(this.options.afterBuildTicks, [this]);
		},

		beforeTickToLabelConversion: function() {
			helpers.callCallback(this.options.beforeTickToLabelConversion, [this]);
		},
		convertTicksToLabels: function() {
			// Convert ticks to strings
			this.ticks = this.ticks.map(function(numericalTick, index, ticks) {
					if (this.options.ticks.userCallback) {
						return this.options.ticks.userCallback(numericalTick, index, ticks);
					}
					return this.options.ticks.callback(numericalTick, index, ticks);
				},
				this);
		},
		afterTickToLabelConversion: function() {
			helpers.callCallback(this.options.afterTickToLabelConversion, [this]);
		},

		//

		beforeCalculateTickRotation: function() {
			helpers.callCallback(this.options.beforeCalculateTickRotation, [this]);
		},
		calculateTickRotation: function() {
			var context = this.ctx;
			var globalDefaults = Chart.defaults.global;
			var optionTicks = this.options.ticks;

			//Get the width of each grid by calculating the difference
			//between x offsets between 0 and 1.
			var tickFontSize = helpers.getValueOrDefault(optionTicks.fontSize, globalDefaults.defaultFontSize);
			var tickFontStyle = helpers.getValueOrDefault(optionTicks.fontStyle, globalDefaults.defaultFontStyle);
			var tickFontFamily = helpers.getValueOrDefault(optionTicks.fontFamily, globalDefaults.defaultFontFamily);
			var tickLabelFont = helpers.fontString(tickFontSize, tickFontStyle, tickFontFamily);
			context.font = tickLabelFont;

			var firstWidth = context.measureText(this.ticks[0]).width;
			var lastWidth = context.measureText(this.ticks[this.ticks.length - 1]).width;
			var firstRotated;

			this.labelRotation = optionTicks.minRotation || 0;
			this.paddingRight = 0;
			this.paddingLeft = 0;

			if (this.options.display) {
				if (this.isHorizontal()) {
					this.paddingRight = lastWidth / 2 + 3;
					this.paddingLeft = firstWidth / 2 + 3;

					if (!this.longestTextCache) {
						this.longestTextCache = {};
					}
					var originalLabelWidth = helpers.longestText(context, tickLabelFont, this.ticks, this.longestTextCache);
					var labelWidth = originalLabelWidth;
					var cosRotation;
					var sinRotation;

					// Allow 3 pixels x2 padding either side for label readability
					// only the index matters for a dataset scale, but we want a consistent interface between scales
					var tickWidth = this.getPixelForTick(1) - this.getPixelForTick(0) - 6;

					//Max label rotation can be set or default to 90 - also act as a loop counter
					while (labelWidth > tickWidth && this.labelRotation < optionTicks.maxRotation) {
						cosRotation = Math.cos(helpers.toRadians(this.labelRotation));
						sinRotation = Math.sin(helpers.toRadians(this.labelRotation));

						firstRotated = cosRotation * firstWidth;

						// We're right aligning the text now.
						if (firstRotated + tickFontSize / 2 > this.yLabelWidth) {
							this.paddingLeft = firstRotated + tickFontSize / 2;
						}

						this.paddingRight = tickFontSize / 2;

						if (sinRotation * originalLabelWidth > this.maxHeight) {
							// go back one step
							this.labelRotation--;
							break;
						}

						this.labelRotation++;
						labelWidth = cosRotation * originalLabelWidth;
					}
				}
			}

			if (this.margins) {
				this.paddingLeft = Math.max(this.paddingLeft - this.margins.left, 0);
				this.paddingRight = Math.max(this.paddingRight - this.margins.right, 0);
			}
		},
		afterCalculateTickRotation: function() {
			helpers.callCallback(this.options.afterCalculateTickRotation, [this]);
		},

		//

		beforeFit: function() {
			helpers.callCallback(this.options.beforeFit, [this]);
		},
		fit: function() {
			// Reset
			var minSize = this.minSize = {
				width: 0,
				height: 0
			};

			var opts = this.options;
			var globalDefaults = Chart.defaults.global;
			var tickOpts = opts.ticks;
			var scaleLabelOpts = opts.scaleLabel;
			var display = opts.display;
			var isHorizontal = this.isHorizontal();

			var tickFontSize = helpers.getValueOrDefault(tickOpts.fontSize, globalDefaults.defaultFontSize);
			var tickFontStyle = helpers.getValueOrDefault(tickOpts.fontStyle, globalDefaults.defaultFontStyle);
			var tickFontFamily = helpers.getValueOrDefault(tickOpts.fontFamily, globalDefaults.defaultFontFamily);
			var tickLabelFont = helpers.fontString(tickFontSize, tickFontStyle, tickFontFamily);

			var scaleLabelFontSize = helpers.getValueOrDefault(scaleLabelOpts.fontSize, globalDefaults.defaultFontSize);
			var scaleLabelFontStyle = helpers.getValueOrDefault(scaleLabelOpts.fontStyle, globalDefaults.defaultFontStyle);
			var scaleLabelFontFamily = helpers.getValueOrDefault(scaleLabelOpts.fontFamily, globalDefaults.defaultFontFamily);
			var scaleLabelFont = helpers.fontString(scaleLabelFontSize, scaleLabelFontStyle, scaleLabelFontFamily);

			var tickMarkLength = opts.gridLines.tickMarkLength;

			// Width
			if (isHorizontal) {
				// subtract the margins to line up with the chartArea if we are a full width scale
				minSize.width = this.isFullWidth() ? this.maxWidth - this.margins.left - this.margins.right : this.maxWidth;
			} else {
				minSize.width = display ? tickMarkLength : 0;
			}

			// height
			if (isHorizontal) {
				minSize.height = display ? tickMarkLength : 0;
			} else {
				minSize.height = this.maxHeight; // fill all the height
			}

			// Are we showing a title for the scale?
			if (scaleLabelOpts.display && display) {
				if (isHorizontal) {
					minSize.height += (scaleLabelFontSize * 1.5);
				} else {
					minSize.width += (scaleLabelFontSize * 1.5);
				}
			}

			if (tickOpts.display && display) {
				// Don't bother fitting the ticks if we are not showing them
				if (!this.longestTextCache) {
					this.longestTextCache = {};
				}

				var largestTextWidth = helpers.longestText(this.ctx, tickLabelFont, this.ticks, this.longestTextCache);

				if (isHorizontal) {
					// A horizontal axis is more constrained by the height.
					this.longestLabelWidth = largestTextWidth;

					// TODO - improve this calculation
					var labelHeight = (Math.sin(helpers.toRadians(this.labelRotation)) * this.longestLabelWidth) + 1.5 * tickFontSize;

					minSize.height = Math.min(this.maxHeight, minSize.height + labelHeight);
					this.ctx.font = tickLabelFont;

					var firstLabelWidth = this.ctx.measureText(this.ticks[0]).width;
					var lastLabelWidth = this.ctx.measureText(this.ticks[this.ticks.length - 1]).width;

					// Ensure that our ticks are always inside the canvas. When rotated, ticks are right aligned which means that the right padding is dominated
					// by the font height
					var cosRotation = Math.cos(helpers.toRadians(this.labelRotation));
					var sinRotation = Math.sin(helpers.toRadians(this.labelRotation));
					this.paddingLeft = this.labelRotation !== 0 ? (cosRotation * firstLabelWidth) + 3 : firstLabelWidth / 2 + 3; // add 3 px to move away from canvas edges
					this.paddingRight = this.labelRotation !== 0 ? (sinRotation * (tickFontSize / 2)) + 3 : lastLabelWidth / 2 + 3; // when rotated
				} else {
					// A vertical axis is more constrained by the width. Labels are the dominant factor here, so get that length first
					var maxLabelWidth = this.maxWidth - minSize.width;

					// Account for padding
					var mirror = tickOpts.mirror;
					if (!mirror) {
						largestTextWidth += this.options.ticks.padding;
					} else {
						// If mirrored text is on the inside so don't expand
						largestTextWidth = 0;
					}

					if (largestTextWidth < maxLabelWidth) {
						// We don't need all the room
						minSize.width += largestTextWidth;
					} else {
						// Expand to max size
						minSize.width = this.maxWidth;
					}

					this.paddingTop = tickFontSize / 2;
					this.paddingBottom = tickFontSize / 2;
				}
			}

			if (this.margins) {
				this.paddingLeft = Math.max(this.paddingLeft - this.margins.left, 0);
				this.paddingTop = Math.max(this.paddingTop - this.margins.top, 0);
				this.paddingRight = Math.max(this.paddingRight - this.margins.right, 0);
				this.paddingBottom = Math.max(this.paddingBottom - this.margins.bottom, 0);
			}

			this.width = minSize.width;
			this.height = minSize.height;

		},
		afterFit: function() {
			helpers.callCallback(this.options.afterFit, [this]);
		},

		// Shared Methods
		isHorizontal: function() {
			return this.options.position === "top" || this.options.position === "bottom";
		},
		isFullWidth: function() {
			return (this.options.fullWidth);
		},

		// Get the correct value. NaN bad inputs, If the value type is object get the x or y based on whether we are horizontal or not
		getRightValue: function getRightValue(rawValue) {
			// Null and undefined values first
			if (rawValue === null || typeof(rawValue) === 'undefined') {
				return NaN;
			}
			// isNaN(object) returns true, so make sure NaN is checking for a number
			if (typeof(rawValue) === 'number' && isNaN(rawValue)) {
				return NaN;
			}
			// If it is in fact an object, dive in one more level
			if (typeof(rawValue) === "object") {
				if ((rawValue instanceof Date) || (rawValue.isValid)) {
					return rawValue;
				} else {
					return getRightValue(this.isHorizontal() ? rawValue.x : rawValue.y);
				}
			}

			// Value is good, return it
			return rawValue;
		},

		// Used to get the value to display in the tooltip for the data at the given index
		// function getLabelForIndex(index, datasetIndex)
		getLabelForIndex: helpers.noop,

		// Used to get data value locations.  Value can either be an index or a numerical value
		getPixelForValue: helpers.noop,

		// Used to get the data value from a given pixel. This is the inverse of getPixelForValue
		getValueForPixel: helpers.noop,

		// Used for tick location, should
		getPixelForTick: function(index, includeOffset) {
			if (this.isHorizontal()) {
				var innerWidth = this.width - (this.paddingLeft + this.paddingRight);
				var tickWidth = innerWidth / Math.max((this.ticks.length - ((this.options.gridLines.offsetGridLines) ? 0 : 1)), 1);
				var pixel = (tickWidth * index) + this.paddingLeft;

				if (includeOffset) {
					pixel += tickWidth / 2;
				}

				var finalVal = this.left + Math.round(pixel);
				finalVal += this.isFullWidth() ? this.margins.left : 0;
				return finalVal;
			} else {
				var innerHeight = this.height - (this.paddingTop + this.paddingBottom);
				return this.top + (index * (innerHeight / (this.ticks.length - 1)));
			}
		},

		// Utility for getting the pixel location of a percentage of scale
		getPixelForDecimal: function(decimal /*, includeOffset*/ ) {
			if (this.isHorizontal()) {
				var innerWidth = this.width - (this.paddingLeft + this.paddingRight);
				var valueOffset = (innerWidth * decimal) + this.paddingLeft;

				var finalVal = this.left + Math.round(valueOffset);
				finalVal += this.isFullWidth() ? this.margins.left : 0;
				return finalVal;
			} else {
				return this.top + (decimal * this.height);
			}
		},

		getBasePixel: function() {
			var me = this;
			var min = me.min;
			var max = me.max;

			return me.getPixelForValue(
				me.beginAtZero? 0:
				min < 0 && max < 0? max :
				min > 0 && max > 0? min :
				0);
		},

		// Actualy draw the scale on the canvas
		// @param {rectangle} chartArea : the area of the chart to draw full grid lines on
		draw: function(chartArea) {
			var options = this.options;
			if (!options.display) {
				return;
			}

			var context = this.ctx;
			var globalDefaults = Chart.defaults.global;
			var optionTicks = options.ticks;
			var gridLines = options.gridLines;
			var scaleLabel = options.scaleLabel;

			var setContextLineSettings;
			var isRotated = this.labelRotation !== 0;
			var skipRatio;
			var scaleLabelX;
			var scaleLabelY;
			var useAutoskipper = optionTicks.autoSkip;

			// figure out the maximum number of gridlines to show
			var maxTicks;
			if (optionTicks.maxTicksLimit) {
				maxTicks = optionTicks.maxTicksLimit;
			}

			var tickFontColor = helpers.getValueOrDefault(optionTicks.fontColor, globalDefaults.defaultFontColor);
			var tickFontSize = helpers.getValueOrDefault(optionTicks.fontSize, globalDefaults.defaultFontSize);
			var tickFontStyle = helpers.getValueOrDefault(optionTicks.fontStyle, globalDefaults.defaultFontStyle);
			var tickFontFamily = helpers.getValueOrDefault(optionTicks.fontFamily, globalDefaults.defaultFontFamily);
			var tickLabelFont = helpers.fontString(tickFontSize, tickFontStyle, tickFontFamily);
			var tl = gridLines.tickMarkLength;

			var scaleLabelFontColor = helpers.getValueOrDefault(scaleLabel.fontColor, globalDefaults.defaultFontColor);
			var scaleLabelFontSize = helpers.getValueOrDefault(scaleLabel.fontSize, globalDefaults.defaultFontSize);
			var scaleLabelFontStyle = helpers.getValueOrDefault(scaleLabel.fontStyle, globalDefaults.defaultFontStyle);
			var scaleLabelFontFamily = helpers.getValueOrDefault(scaleLabel.fontFamily, globalDefaults.defaultFontFamily);
			var scaleLabelFont = helpers.fontString(scaleLabelFontSize, scaleLabelFontStyle, scaleLabelFontFamily);

			var labelRotationRadians = helpers.toRadians(this.labelRotation);
			var cosRotation = Math.cos(labelRotationRadians);
			var sinRotation = Math.sin(labelRotationRadians);
			var longestRotatedLabel = this.longestLabelWidth * cosRotation;
			var rotatedLabelHeight = tickFontSize * sinRotation;

			// Make sure we draw text in the correct color and font
			context.fillStyle = tickFontColor;

			if (this.isHorizontal()) {
				setContextLineSettings = true;
				var yTickStart = options.position === "bottom" ? this.top : this.bottom - tl;
				var yTickEnd = options.position === "bottom" ? this.top + tl : this.bottom;
				skipRatio = false;

                // Only calculate the skip ratio with the half width of longestRotateLabel if we got an actual rotation
                // See #2584
                if (isRotated) {
                    longestRotatedLabel /= 2;
                }

				if ((longestRotatedLabel + optionTicks.autoSkipPadding) * this.ticks.length > (this.width - (this.paddingLeft + this.paddingRight))) {
					skipRatio = 1 + Math.floor(((longestRotatedLabel + optionTicks.autoSkipPadding) * this.ticks.length) / (this.width - (this.paddingLeft + this.paddingRight)));
				}

				// if they defined a max number of optionTicks,
				// increase skipRatio until that number is met
				if (maxTicks && this.ticks.length > maxTicks) {
					while (!skipRatio || this.ticks.length / (skipRatio || 1) > maxTicks) {
						if (!skipRatio) {
							skipRatio = 1;
						}
						skipRatio += 1;
					}
				}

				if (!useAutoskipper) {
					skipRatio = false;
				}

				helpers.each(this.ticks, function (label, index) {
					// Blank optionTicks
					var isLastTick = this.ticks.length === index + 1;

					// Since we always show the last tick,we need may need to hide the last shown one before
					var shouldSkip = (skipRatio > 1 && index % skipRatio > 0) || (index % skipRatio === 0 && index + skipRatio >= this.ticks.length);
					if (shouldSkip && !isLastTick || (label === undefined || label === null)) {
						return;
					}
					var xLineValue = this.getPixelForTick(index); // xvalues for grid lines
					var xLabelValue = this.getPixelForTick(index, gridLines.offsetGridLines); // x values for optionTicks (need to consider offsetLabel option)

					if (gridLines.display) {
						if (index === (typeof this.zeroLineIndex !== 'undefined' ? this.zeroLineIndex : 0)) {
							// Draw the first index specially
							context.lineWidth = gridLines.zeroLineWidth;
							context.strokeStyle = gridLines.zeroLineColor;
							setContextLineSettings = true; // reset next time
						} else if (setContextLineSettings) {
							context.lineWidth = gridLines.lineWidth;
							context.strokeStyle = gridLines.color;
							setContextLineSettings = false;
						}

						xLineValue += helpers.aliasPixel(context.lineWidth);

						// Draw the label area
						context.beginPath();

						if (gridLines.drawTicks) {
							context.moveTo(xLineValue, yTickStart);
							context.lineTo(xLineValue, yTickEnd);
						}

						// Draw the chart area
						if (gridLines.drawOnChartArea) {
							context.moveTo(xLineValue, chartArea.top);
							context.lineTo(xLineValue, chartArea.bottom);
						}

						// Need to stroke in the loop because we are potentially changing line widths & colours
						context.stroke();
					}

					if (optionTicks.display) {
						context.save();
						context.translate(xLabelValue + optionTicks.labelOffset, (isRotated) ? this.top + 12 : options.position === "top" ? this.bottom - tl : this.top + tl);
						context.rotate(labelRotationRadians * -1);
						context.font = tickLabelFont;
						context.textAlign = (isRotated) ? "right" : "center";
						context.textBaseline = (isRotated) ? "middle" : options.position === "top" ? "bottom" : "top";
						context.fillText(label, 0, 0);
						context.restore();
					}
				}, this);

				if (scaleLabel.display) {
					// Draw the scale label
					context.textAlign = "center";
					context.textBaseline = 'middle';
					context.fillStyle = scaleLabelFontColor; // render in correct colour
					context.font = scaleLabelFont;

					scaleLabelX = this.left + ((this.right - this.left) / 2); // midpoint of the width
					scaleLabelY = options.position === 'bottom' ? this.bottom - (scaleLabelFontSize / 2) : this.top + (scaleLabelFontSize / 2);

					context.fillText(scaleLabel.labelString, scaleLabelX, scaleLabelY);
				}

			} else {
				setContextLineSettings = true;
				var xTickStart = options.position === "right" ? this.left : this.right - 5;
				var xTickEnd = options.position === "right" ? this.left + 5 : this.right;

				helpers.each(this.ticks, function (label, index) {
					// If the callback returned a null or undefined value, do not draw this line
					if (label === undefined || label === null) {
						return;
					}

					var yLineValue = this.getPixelForTick(index); // xvalues for grid lines

					if (gridLines.display) {
						if (index === (typeof this.zeroLineIndex !== 'undefined' ? this.zeroLineIndex : 0)) {
							// Draw the first index specially
							context.lineWidth = gridLines.zeroLineWidth;
							context.strokeStyle = gridLines.zeroLineColor;
							setContextLineSettings = true; // reset next time
						} else if (setContextLineSettings) {
							context.lineWidth = gridLines.lineWidth;
							context.strokeStyle = gridLines.color;
							setContextLineSettings = false;
						}

						yLineValue += helpers.aliasPixel(context.lineWidth);

						// Draw the label area
						context.beginPath();

						if (gridLines.drawTicks) {
							context.moveTo(xTickStart, yLineValue);
							context.lineTo(xTickEnd, yLineValue);
						}

						// Draw the chart area
						if (gridLines.drawOnChartArea) {
							context.moveTo(chartArea.left, yLineValue);
							context.lineTo(chartArea.right, yLineValue);
						}

						// Need to stroke in the loop because we are potentially changing line widths & colours
						context.stroke();
					}

					if (optionTicks.display) {
						var xLabelValue;
						var yLabelValue = this.getPixelForTick(index, gridLines.offsetGridLines); // x values for optionTicks (need to consider offsetLabel option)

						context.save();

						if (options.position === "left") {
							if (optionTicks.mirror) {
								xLabelValue = this.right + optionTicks.padding;
								context.textAlign = "left";
							} else {
								xLabelValue = this.right - optionTicks.padding;
								context.textAlign = "right";
							}
						} else {
							// right side
							if (optionTicks.mirror) {
								xLabelValue = this.left - optionTicks.padding;
								context.textAlign = "right";
							} else {
								xLabelValue = this.left + optionTicks.padding;
								context.textAlign = "left";
							}
						}

						context.translate(xLabelValue, yLabelValue + optionTicks.labelOffset);
						context.rotate(labelRotationRadians * -1);
						context.font = tickLabelFont;
						context.textBaseline = "middle";
						context.fillText(label, 0, 0);
						context.restore();
					}
				}, this);

				if (scaleLabel.display) {
					// Draw the scale label
					scaleLabelX = options.position === 'left' ? this.left + (scaleLabelFontSize / 2) : this.right - (scaleLabelFontSize / 2);
					scaleLabelY = this.top + ((this.bottom - this.top) / 2);
					var rotation = options.position === 'left' ? -0.5 * Math.PI : 0.5 * Math.PI;

					context.save();
					context.translate(scaleLabelX, scaleLabelY);
					context.rotate(rotation);
					context.textAlign = "center";
					context.fillStyle = scaleLabelFontColor; // render in correct colour
					context.font = scaleLabelFont;
					context.textBaseline = 'middle';
					context.fillText(scaleLabel.labelString, 0, 0);
					context.restore();
				}
			}

			if (gridLines.drawBorder) {
				// Draw the line at the edge of the axis
				context.lineWidth = gridLines.lineWidth;
				context.strokeStyle = gridLines.color;
				var x1 = this.left,
					x2 = this.right,
					y1 = this.top,
					y2 = this.bottom;

				var aliasPixel = helpers.aliasPixel(context.lineWidth);
				if (this.isHorizontal()) {
					y1 = y2 = options.position === 'top' ? this.bottom : this.top;
					y1 += aliasPixel;
					y2 += aliasPixel;
				} else {
					x1 = x2 = options.position === 'left' ? this.right : this.left;
					x1 += aliasPixel;
					x2 += aliasPixel;
				}

				context.beginPath();
				context.moveTo(x1, y1);
				context.lineTo(x2, y2);
				context.stroke();
			}
		}
	});
};