Include helpers._alignPixel only once (#6735)

Author: benmccann

docs/getting-started/v3-migration.md

@@ -91,6 +91,10 @@ Chart.js is no longer providing the `Chart.bundle.js` and `Chart.bundle.min.js`.
 * `TimeScale.tickFormatFunction` was renamed to `TimeScale._tickFormatFunction`
 * `TimeScale.getPixelForOffset` was renamed to `TimeScale._getPixelForOffset`
 
+#### Renamed private APIs
+
+* `helpers._alignPixel` was renamed to `helpers.canvas._alignPixel`
+
 ### Changed
 
 #### Scales

src/core/core.helpers.js

@@ -152,20 +152,6 @@ module.exports = function() {
 		return Math.sqrt(Math.pow(pt2.x - pt1.x, 2) + Math.pow(pt2.y - pt1.y, 2));
 	};
 
-	/**
-	 * Returns the aligned pixel value to avoid anti-aliasing blur
-	 * @param {Chart} chart - The chart instance.
-	 * @param {number} pixel - A pixel value.
-	 * @param {number} width - The width of the element.
-	 * @returns {number} The aligned pixel value.
-	 * @private
-	 */
-	helpers._alignPixel = function(chart, pixel, width) {
-		var devicePixelRatio = chart.currentDevicePixelRatio;
-		var halfWidth = width / 2;
-		return Math.round((pixel - halfWidth) * devicePixelRatio) / devicePixelRatio + halfWidth;
-	};
-
 	helpers.splineCurve = function(firstPoint, middlePoint, afterPoint, t) {
 		// Props to Rob Spencer at scaled innovation for his post on splining between points
 		// http://scaledinnovation.com/analytics/splines/aboutSplines.html

src/core/core.scale.js

@@ -5,6 +5,7 @@ const Element = require('./core.element');
 const helpers = require('../helpers/index');
 const Ticks = require('./core.ticks');
 
+const alignPixel = helpers.canvas._alignPixel;
 const isArray = helpers.isArray;
 const isFinite = helpers.isFinite;
 const isNullOrUndef = helpers.isNullOrUndef;
@@ -998,7 +999,6 @@ class Scale extends Element {
 		};
 		var axisWidth = gridLines.drawBorder ? resolve([gridLines.lineWidth, 0], context, 0) : 0;
 		var axisHalfWidth = axisWidth / 2;
-		var alignPixel = helpers._alignPixel;
 		var alignBorderValue = function(pixel) {
 			return alignPixel(chart, pixel, axisWidth);
 		};
@@ -1159,7 +1159,6 @@ class Scale extends Element {
 
 		var ctx = me.ctx;
 		var chart = me.chart;
-		var alignPixel = helpers._alignPixel;
 		var context = {
 			scale: me,
 			tick: me.ticks[0],

src/helpers/helpers.canvas.js

@@ -1,16 +1,30 @@
 'use strict';
 
-var PI = Math.PI;
-var RAD_PER_DEG = PI / 180;
-var DOUBLE_PI = PI * 2;
-var HALF_PI = PI / 2;
-var QUARTER_PI = PI / 4;
-var TWO_THIRDS_PI = PI * 2 / 3;
+const PI = Math.PI;
+const RAD_PER_DEG = PI / 180;
+const DOUBLE_PI = PI * 2;
+const HALF_PI = PI / 2;
+const QUARTER_PI = PI / 4;
+const TWO_THIRDS_PI = PI * 2 / 3;
 
 /**
  * @namespace Chart.helpers.canvas
  */
-var exports = {
+module.exports = {
+	/**
+	 * Returns the aligned pixel value to avoid anti-aliasing blur
+	 * @param {Chart} chart - The chart instance.
+	 * @param {number} pixel - A pixel value.
+	 * @param {number} width - The width of the element.
+	 * @returns {number} The aligned pixel value.
+	 * @private
+	 */
+	_alignPixel: function(chart, pixel, width) {
+		const devicePixelRatio = chart.currentDevicePixelRatio;
+		const halfWidth = width / 2;
+		return Math.round((pixel - halfWidth) * devicePixelRatio) / devicePixelRatio + halfWidth;
+	},
+
 	/**
 	 * Clears the entire canvas associated to the given `chart`.
 	 * @param {Chart} chart - The chart for which to clear the canvas.
@@ -229,5 +243,3 @@ var exports = {
 			target.y);
 	}
 };
-
-module.exports = exports;