From cb54f30c970672488a239a2d371d55dfe3fb8864 Mon Sep 17 00:00:00 2001
From: Evert Timberg <evert.timberg+github@gmail.com>
Date: Sat, 30 Apr 2016 08:39:18 -0400
Subject: [PATCH] Implement getValueForPixel for category scale

---
 src/scales/scale.category.js | 21 +++++++++++++++++++++
 test/scale.category.tests.js | 11 +++++++++++
 2 files changed, 32 insertions(+)

diff --git a/src/scales/scale.category.js b/src/scales/scale.category.js
index 5b096fef1..6cde7200f 100644
--- a/src/scales/scale.category.js
+++ b/src/scales/scale.category.js
@@ -69,6 +69,27 @@ module.exports = function(Chart) {
 		},
 		getPixelForTick: function(index, includeOffset) {
 			return this.getPixelForValue(this.ticks[index], index + this.minIndex, null, includeOffset);
+		},
+		getValueForPixel: function(pixel)
+		{
+			var value
+;			var offsetAmt = Math.max((this.ticks.length - ((this.options.gridLines.offsetGridLines) ? 0 : 1)), 1);
+			var horz = this.isHorizontal();
+			var innerDimension = horz ? this.width - (this.paddingLeft + this.paddingRight) : this.height - (this.paddingTop + this.paddingBottom);
+			var valueDimension = innerDimension / offsetAmt;
+
+			if (this.options.gridLines.offsetGridLines) {
+				pixel -= (valueDimension / 2);
+			}
+			pixel -= horz ? this.paddingLeft : this.paddingTop;
+
+			if (pixel <= 0) {
+				value = 0;
+			} else {
+				value = Math.round(pixel / valueDimension);
+			}
+
+			return value;
 		}
 	});
 
diff --git a/test/scale.category.tests.js b/test/scale.category.tests.js
index 3303448b6..c26a875c2 100644
--- a/test/scale.category.tests.js
+++ b/test/scale.category.tests.js
@@ -146,17 +146,23 @@ describe('Category scale tests', function() {
 
 		expect(scale.getPixelForValue(0, 0, 0, false)).toBe(33);
 		expect(scale.getPixelForValue(0, 0, 0, true)).toBe(85);
+		expect(scale.getValueForPixel(33)).toBe(0);
+		expect(scale.getValueForPixel(85)).toBe(0);
 
 		expect(scale.getPixelForValue(0, 4, 0, false)).toBe(452);
 		expect(scale.getPixelForValue(0, 4, 0, true)).toBe(505);
+		expect(scale.getValueForPixel(452)).toBe(4);
+		expect(scale.getValueForPixel(505)).toBe(4);
 
 		config.gridLines.offsetGridLines = false;
 
 		expect(scale.getPixelForValue(0, 0, 0, false)).toBe(33);
 		expect(scale.getPixelForValue(0, 0, 0, true)).toBe(33);
+		expect(scale.getValueForPixel(33)).toBe(0);
 
 		expect(scale.getPixelForValue(0, 4, 0, false)).toBe(557);
 		expect(scale.getPixelForValue(0, 4, 0, true)).toBe(557);
+		expect(scale.getValueForPixel(557)).toBe(4);
 	});
 
 	it ('Should get the correct pixel for a value when horizontal and zoomed', function() {
@@ -268,17 +274,22 @@ describe('Category scale tests', function() {
 
 		expect(scale.getPixelForValue(0, 0, 0, false)).toBe(11);
 		expect(scale.getPixelForValue(0, 0, 0, true)).toBe(30);
+		expect(scale.getValueForPixel(11)).toBe(0);
+		expect(scale.getValueForPixel(30)).toBe(0);
 
 		expect(scale.getPixelForValue(0, 4, 0, false)).toBe(161);
 		expect(scale.getPixelForValue(0, 4, 0, true)).toBe(180);
+		expect(scale.getValueForPixel(161)).toBe(4);
 
 		config.gridLines.offsetGridLines = false;
 
 		expect(scale.getPixelForValue(0, 0, 0, false)).toBe(11);
 		expect(scale.getPixelForValue(0, 0, 0, true)).toBe(11);
+		expect(scale.getValueForPixel(11)).toBe(0);
 
 		expect(scale.getPixelForValue(0, 4, 0, false)).toBe(199);
 		expect(scale.getPixelForValue(0, 4, 0, true)).toBe(199);
+		expect(scale.getValueForPixel(199)).toBe(4);
 	});
 
 	it ('should get the correct pixel for a value when vertical and zoomed', function() {
-- 
2.47.3