Add ticks.integerSteps option to linear scale. When true, and

`stepSize`, is not specified, the generated step size will be increased
to the nearest integer value.

docs/axes/cartesian/linear.md

@@ -9,6 +9,7 @@ The following options are provided by the linear scale. They are all located in
 | Name | Type | Default | Description
 | -----| ---- | --------| -----------
 | `beginAtZero` | `Boolean` | | if true, scale will include 0 if it is not already included.
+| `integerSteps` | `Boolean` | | if true and `stepSize` is not specified, the step size will be increased to the next integer value.
 | `min` | `Number` | | User defined minimum number for the scale, overrides minimum value from data. [more...](#axis-range-settings)
 | `max` | `Number` | | User defined maximum number for the scale, overrides maximum value from data. [more...](#axis-range-settings)
 | `maxTicksLimit` | `Number` | `11` | Maximum number of ticks and gridlines to show.

docs/axes/radial/linear.md

@@ -24,6 +24,7 @@ The following options are provided by the linear scale. They are all located in
 | `backdropPaddingX` | `Number` | `2` | Horizontal padding of label backdrop.
 | `backdropPaddingY` | `Number` | `2` | Vertical padding of label backdrop.
 | `beginAtZero` | `Boolean` | `false` | if true, scale will include 0 if it is not already included.
+| `integerSteps` | `Boolean` | | if true and `stepSize` is not specified, the step size will be increased to the next integer value.
 | `min` | `Number` | | User defined minimum number for the scale, overrides minimum value from data. [more...](#axis-range-settings)
 | `max` | `Number` | | User defined maximum number for the scale, overrides maximum value from data. [more...](#axis-range-settings)
 | `maxTicksLimit` | `Number` | `11` | Maximum number of ticks and gridlines to show.

src/core/core.ticks.js

@@ -39,6 +39,12 @@ module.exports = {
 		 * @type Number
 		 * @optional
 		 */
+		/**
+		 * If true and tick spacing is auto generated, the spacing will be an integer.
+		 * @name INumericTickGenerationOptions#integerSteps
+		 * @type Boolean
+		 * @optional
+		 */
 
 		/**
 		 * Generate a set of linear ticks
@@ -59,6 +65,11 @@ module.exports = {
 			} else {
 				var niceRange = helpers.niceNum(dataRange.max - dataRange.min, false);
 				spacing = helpers.niceNum(niceRange / (generationOptions.maxTicks - 1), true);
+
+				if (generationOptions.integerSteps && spacing !== Math.round(spacing)) {
+					// If forcing integer steps, and our step is not an integer, scale up
+					spacing = Math.ceil(spacing);
+				}
 			}
 			var niceMin = Math.floor(dataRange.min / spacing) * spacing;
 			var niceMax = Math.ceil(dataRange.max / spacing) * spacing;

src/scales/scale.linearbase.js

@@ -100,6 +100,7 @@ module.exports = function(Chart) {
 				maxTicks: maxTicks,
 				min: tickOpts.min,
 				max: tickOpts.max,
+				integerSteps: tickOpts.integerSteps,
 				stepSize: helpers.valueOrDefault(tickOpts.fixedStepSize, tickOpts.stepSize)
 			};
 			var ticks = me.ticks = Ticks.generators.linear(numericGeneratorOptions, me);

test/specs/scale.linear.tests.js

@@ -548,6 +548,34 @@ describe('Linear Scale', function() {
 		expect(chart.scales.yScale0.ticks).toEqual(['11', '9', '7', '5', '3', '1']);
 	});
 
+	it('Should create integer steps if integerSteps is true', function() {
+		var chart = window.acquireChart({
+			type: 'bar',
+			data: {
+				datasets: [{
+					yAxisID: 'yScale0',
+					data: [0, 1, 2, 1, 0, 1]
+				}],
+				labels: ['a', 'b', 'c', 'd', 'e', 'f']
+			},
+			options: {
+				scales: {
+					yAxes: [{
+						id: 'yScale0',
+						type: 'linear',
+						ticks: {
+							integerSteps: true
+						}
+					}]
+				}
+			}
+		});
+
+		expect(chart.scales.yScale0).not.toEqual(undefined); // must construct
+		expect(chart.scales.yScale0.min).toBe(0);
+		expect(chart.scales.yScale0.max).toBe(2);
+		expect(chart.scales.yScale0.ticks).toEqual(['2', '1', '0']);
+	});
 
 	it('should forcibly include 0 in the range if the beginAtZero option is used', function() {
 		var chart = window.acquireChart({