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

docs/general/interactions/README.md

@@ -6,4 +6,5 @@ The hover configuration is passed into the `options.hover` namespace. The global
 | ---- | ---- | ------- | -----------
 | `mode` | `String` | `'nearest'` | Sets which elements appear in the tooltip. See [Interaction Modes](./modes.md#interaction-modes) for details.
 | `intersect` | `Boolean` | `true` | if true, the hover mode only applies when the mouse position intersects an item on the chart.
+| `axis` | `String` | `'x'` | Can be set to `'x'`, `'y'`, or `'xy'` to define which directions are used in calculating distances. Defaults to `'x'` for `index` mode and `'xy'` in `dataset` and `nearest` modes.
 | `animationDuration` | `Number` | `400` | Duration in milliseconds it takes to animate hover style changes.

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, {
 })
 ```
 
+To use index mode in a chart like the horizontal bar chart, where we search along the y direction, you can use the `axis` setting introduced in v2.7.0. By setting this value to `'y'` on the y direction is used.
+
+```javascript
+var chart = new Chart(ctx, {
+    type: 'horizontalBar',
+    data: data,
+    options: {
+        tooltips: {
+            mode: 'index',
+            axis: 'y'
+        }
+    }
+})
+```
+
 ## x-axis (deprecated)
 Behaves like `'index'` mode with `intersect = false`.
 

src/controllers/controller.bar.js

@@ -31,7 +31,8 @@ defaults._set('bar', {
 
 defaults._set('horizontalBar', {
 	hover: {
-		mode: 'label'
+		mode: 'index',
+		axis: 'y'
 	},
 
 	scales: {
@@ -82,7 +83,9 @@ defaults._set('horizontalBar', {
 				var datasetLabel = data.datasets[item.datasetIndex].label || '';
 				return datasetLabel + ': ' + item.xLabel;
 			}
-		}
+		},
+		mode: 'index',
+		axis: 'y'
 	}
 });
 

src/core/core.interaction.js

@@ -66,17 +66,13 @@ function getIntersectItems(chart, position) {
  * @param chart {Chart} the chart to look at elements from
  * @param position {Point} the point to be nearest to
  * @param intersect {Boolean} if true, only consider items that intersect the position
- * @param distanceMetric {Function} Optional function to provide the distance between
+ * @param distanceMetric {Function} function to provide the distance between points
  * @return {ChartElement[]} the nearest items
  */
 function getNearestItems(chart, position, intersect, distanceMetric) {
 	var minDistance = Number.POSITIVE_INFINITY;
 	var nearestItems = [];
 
-	if (!distanceMetric) {
-		distanceMetric = helpers.distanceBetweenPoints;
-	}
-
 	parseVisibleItems(chart, function(element) {
 		if (intersect && !element.inRange(position.x, position.y)) {
 			return;
@@ -97,11 +93,27 @@ function getNearestItems(chart, position, intersect, distanceMetric) {
 	return nearestItems;
 }
 
+/**
+ * Get a distance metric function for two points based on the
+ * axis mode setting
+ * @param {String} axis the axis mode. x|y|xy
+ */
+function getDistanceMetricForAxis(axis) {
+	var useX = axis.indexOf('x') !== -1;
+	var useY = axis.indexOf('y') !== -1;
+
+	return function(pt1, pt2) {
+		var deltaX = useX ? Math.abs(pt1.x - pt2.x) : 0;
+		var deltaY = useY ? Math.abs(pt1.y - pt2.y) : 0;
+		return Math.sqrt(Math.pow(deltaX, 2) + Math.pow(deltaY, 2));
+	};
+}
+
 function indexMode(chart, e, options) {
 	var position = getRelativePosition(e, chart);
-	var distanceMetric = function(pt1, pt2) {
-		return Math.abs(pt1.x - pt2.x);
-	};
+	// Default axis for index mode is 'x' to match old behaviour
+	options.axis = options.axis || 'x';
+	var distanceMetric = getDistanceMetricForAxis(options.axis);
 	var items = options.intersect ? getIntersectItems(chart, position) : getNearestItems(chart, position, false, distanceMetric);
 	var elements = [];
 
@@ -185,7 +197,9 @@ module.exports = {
 		 */
 		dataset: function(chart, e, options) {
 			var position = getRelativePosition(e, chart);
-			var items = options.intersect ? getIntersectItems(chart, position) : getNearestItems(chart, position, false);
+			options.axis = options.axis || 'xy';
+			var distanceMetric = getDistanceMetricForAxis(options.axis);
+			var items = options.intersect ? getIntersectItems(chart, position) : getNearestItems(chart, position, false, distanceMetric);
 
 			if (items.length > 0) {
 				items = chart.getDatasetMeta(items[0]._datasetIndex).data;
@@ -201,7 +215,7 @@ module.exports = {
 		 * @private
 		 */
 		'x-axis': function(chart, e) {
-			return indexMode(chart, e, true);
+			return indexMode(chart, e, {intersect: true});
 		},
 
 		/**
@@ -227,7 +241,9 @@ module.exports = {
 		 */
 		nearest: function(chart, e, options) {
 			var position = getRelativePosition(e, chart);
-			var nearestItems = getNearestItems(chart, position, options.intersect);
+			options.axis = options.axis || 'xy';
+			var distanceMetric = getDistanceMetricForAxis(options.axis);
+			var nearestItems = getNearestItems(chart, position, options.intersect, distanceMetric);
 
 			// We have multiple items at the same distance from the event. Now sort by smallest
 			if (nearestItems.length > 1) {