From 2ddcb6d740c7e7c4a31db479918a8a0a47a0171e Mon Sep 17 00:00:00 2001
From: Aidan Fewster <fewstera@gmail.com>
Date: Tue, 4 Oct 2016 11:53:55 +0100
Subject: [PATCH] If tick options have min, max and stepSize use them to
 generate evenly spaced ticks

---
 src/core/core.ticks.js     | 11 ++++++++++-
 test/scale.linear.tests.js | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/src/core/core.ticks.js b/src/core/core.ticks.js
index f55b8d40e0a..78ec07c3b94 100644
--- a/src/core/core.ticks.js
+++ b/src/core/core.ticks.js
@@ -64,8 +64,17 @@ module.exports = function(Chart) {
 				}
 				var niceMin = Math.floor(dataRange.min / spacing) * spacing;
 				var niceMax = Math.ceil(dataRange.max / spacing) * spacing;
-				var numSpaces = (niceMax - niceMin) / spacing;
 
+				// If min, max and stepSize is set and they make an evenly spaced scale use it.
+				if (generationOptions.min && generationOptions.max && generationOptions.stepSize) {
+					var minMaxDeltaDivisableByStepSize = ((generationOptions.max - generationOptions.min) % generationOptions.stepSize) === 0;
+					if (minMaxDeltaDivisableByStepSize) {
+						niceMin = generationOptions.min;
+						niceMax = generationOptions.max;
+					}
+				}
+
+				var numSpaces = (niceMax - niceMin) / spacing;
 				// If very close to our rounded value, use it.
 				if (helpers.almostEquals(numSpaces, Math.round(numSpaces), spacing / 1000)) {
 					numSpaces = Math.round(numSpaces);
diff --git a/test/scale.linear.tests.js b/test/scale.linear.tests.js
index 3df77325848..4eb585a7b66 100644
--- a/test/scale.linear.tests.js
+++ b/test/scale.linear.tests.js
@@ -486,6 +486,38 @@ describe('Linear Scale', function() {
 		expect(chart.scales.yScale0.ticks[chart.scales.yScale0.ticks.length - 1]).toBe('-1010');
 	});
 
+	it('Should use min, max and stepSize to create fixed spaced ticks', function() {
+		var chart = window.acquireChart({
+			type: 'bar',
+			data: {
+				datasets: [{
+					yAxisID: 'yScale0',
+					data: [10, 3, 6, 8, 3, 1]
+				}],
+				labels: ['a', 'b', 'c', 'd', 'e', 'f']
+			},
+			options: {
+				scales: {
+					yAxes: [{
+						id: 'yScale0',
+						type: 'linear',
+						ticks: {
+							min: 1,
+							max: 11,
+							stepSize: 2
+						}
+					}]
+				}
+			}
+		});
+
+		expect(chart.scales.yScale0).not.toEqual(undefined); // must construct
+		expect(chart.scales.yScale0.min).toBe(1);
+		expect(chart.scales.yScale0.max).toBe(11);
+		expect(chart.scales.yScale0.ticks).toEqual(['11', '9', '7', '5', '3', '1']);
+	});
+
+
 	it('should forcibly include 0 in the range if the beginAtZero option is used', function() {
 		var chart = window.acquireChart({
 			type: 'bar',