index-y interaction mode + convert horizontal bar defaults to new mode

docs/general/interactions/modes.md

@@ -41,7 +41,7 @@ Finds the first item that intersects the point and returns it. Behaves like 'nea
 See `'index'` mode
 
 ## index
-Finds item at the same index. If the `intersect` setting is true, the first intersecting item is used to determine the index in the data. If `intersect` false the nearest item is used to determine the index. 
+Finds item at the same index. If the `intersect` setting is true, the first intersecting item is used to determine the index in the data. If `intersect` false the nearest item, in the x direction, is used to determine the index. 
 
 ```javascript
 var chart = new Chart(ctx, {
@@ -55,6 +55,21 @@ var chart = new Chart(ctx, {
 })
 ```
 
+## index-y
+Finds the item at the same index along the Y axis. If the `intersect` setting is true, the first intersecting item is used to determine the index in the data. If `intersect` false the nearest item, in the y direction, is used to determine the index. 
+
+```javascript
+var chart = new Chart(ctx, {
+    type: 'line',
+    data: data,
+    options: {
+        tooltips: {
+            mode: 'index-y'
+        }
+    }
+})
+```
+
 ## x-axis (deprecated)
 Behaves like `'index'` mode with `intersect = false`.
 

src/controllers/controller.bar.js

@@ -314,7 +314,7 @@ module.exports = function(Chart) {
 	// it extends bar (like pie extends doughnut)
 	Chart.defaults.horizontalBar = {
 		hover: {
-			mode: 'label'
+			mode: 'index-y'
 		},
 
 		scales: {
@@ -361,7 +361,8 @@ module.exports = function(Chart) {
 					var datasetLabel = data.datasets[tooltipItem.datasetIndex].label || '';
 					return datasetLabel + ': ' + tooltipItem.xLabel;
 				}
-			}
+			},
+			mode: 'index-y'
 		}
 	};
 

src/core/core.interaction.js

@@ -98,32 +98,37 @@ module.exports = function(Chart) {
 		return nearestItems;
 	}
 
-	function indexMode(chart, e, options) {
-		var position = getRelativePosition(e, chart);
-		var distanceMetric = function(pt1, pt2) {
-			return Math.abs(pt1.x - pt2.x);
-		};
-		var items = options.intersect ? getIntersectItems(chart, position) : getNearestItems(chart, position, false, distanceMetric);
-		var elements = [];
-
-		if (!items.length) {
-			return [];
-		}
+	function buildIndexMode(distanceMetric) {
+		return function(chart, e, options) {
+			var position = getRelativePosition(e, chart);
+			var items = options.intersect ? getIntersectItems(chart, position) : getNearestItems(chart, position, false, distanceMetric);
+			var elements = [];
+
+			if (!items.length) {
+				return [];
+			}
 
-		chart.data.datasets.forEach(function(dataset, datasetIndex) {
-			if (chart.isDatasetVisible(datasetIndex)) {
-				var meta = chart.getDatasetMeta(datasetIndex),
-					element = meta.data[items[0]._index];
+			chart.data.datasets.forEach(function(dataset, datasetIndex) {
+				if (chart.isDatasetVisible(datasetIndex)) {
+					var meta = chart.getDatasetMeta(datasetIndex),
+						element = meta.data[items[0]._index];
 
-				// don't count items that are skipped (null data)
-				if (element && !element._view.skip) {
-					elements.push(element);
+					// don't count items that are skipped (null data)
+					if (element && !element._view.skip) {
+						elements.push(element);
+					}
 				}
-			}
-		});
+			});
 
-		return elements;
+			return elements;
+		};
 	}
+	var indexMode = buildIndexMode(function(pt1, pt2) {
+		return Math.abs(pt1.x - pt2.x);
+	});
+	var indexYMode = buildIndexMode(function(pt1, pt2) {
+		return Math.abs(pt1.y - pt2.y);
+	});
 
 	/**
 	 * @interface IInteractionOptions
@@ -175,6 +180,19 @@ module.exports = function(Chart) {
 			 */
 			index: indexMode,
 
+			/**
+			 * Returns items at the same label along the Y axis
+			 * If the options.intersect parameter is true, we only return items if we intersect something
+			 * If the options.intersect mode is false, we find the nearest item and return the items at the same index as that item
+			 * @function Chart.Interaction.modes.index-y
+			 * @since v2.7.0
+			 * @param chart {chart} the chart we are returning items from
+			 * @param e {Event} the event we are find things at
+			 * @param options {IInteractionOptions} options to use during interaction
+			 * @return {Chart.Element[]} Array of elements that are under the point. If none are found, an empty array is returned
+			 */
+			'index-y': indexYMode,
+
 			/**
 			 * Returns items in the same dataset. If the options.intersect parameter is true, we only return items if we intersect something
 			 * If the options.intersect is false, we find the nearest item and return the items in that dataset