Fixed #6420, When multiple axes, show only one snapping crosshair at …

…the same time.

js/parts/Pointer.js

@@ -371,20 +371,18 @@ H.Pointer.prototype = {
 				}
 			});
 		}
-		
-		// Draw crosshairs (#4927, #5269 #5066, #5658)
+
+		// Issues related to crosshair #4927, #5269 #5066, #5658
 		each(chart.axes, function drawAxisCrosshair(axis) {
-			// Snap is true. For each hover point, loop over the axes and draw a
-			// crosshair if that point belongs to the axis.
-			// @todo Consider only one crosshair per axis.
-			if (pick(axis.crosshair.snap, true)) {
-				each(points, function (p) {
-					if (p.series[axis.coll] === axis) {
-						axis.drawCrosshair(e, p);
-					}
-				});
-			} else {
+			var snap = pick(axis.crosshair.snap, true);
+			if (!snap) {
 				axis.drawCrosshair(e);
+			// axis has snapping crosshairs, and hover point is belonging to axis
+			} else if (hoverPoint && hoverPoint.series[axis.coll] === axis) {
+				axis.drawCrosshair(e, hoverPoint);
+			// axis has snapping crosshairs, but hover point is not belonging to axis
+			} else {
+				axis.hideCrosshair();
 			}
 		});
 	},

samples/unit-tests/axis/crosshairs/demo.js

@@ -63,4 +63,50 @@ QUnit.test('snap', function (assert) {
     // );
 
     // TODO Test positioning of crosshairs.
-});
+});
+
+QUnit.test('Show only one snapping crosshair at the same time. #6420', function (assert) {
+    var chart = Highcharts.chart('container', {
+            xAxis: [{
+                crosshair: true
+            }, {
+                opposite: true,
+                crosshair: true
+            }],
+            series: [{
+                name: 'Installation',
+                data: [1, 2, 3],
+                xAxis: 0
+            }, {
+                name: 'Manufacturing',
+                data: [1, 2, 3].reverse(),
+                xAxis: 1
+            }]
+        }),
+        series1 = chart.series[0],
+        series2 = chart.series[1];
+
+    series1.points[0].onMouseOver();
+    assert.strictEqual(
+        series1.xAxis.cross.attr('visibility'),
+        'visible',
+        'Hover Series 1: crosshair on xAxis of Series 1 is visible'
+    );
+    assert.strictEqual(
+        !!series2.xAxis.cross,
+        false,
+        'Hover Series 1: crosshair on xAxis of Series 2 does not exist'
+    );
+
+    series2.points[2].onMouseOver();
+    assert.strictEqual(
+        series1.xAxis.cross.attr('visibility'),
+        'hidden',
+        'Hover Series 2: crosshair on xAxis of Series 1 is hidden'
+    );
+    assert.strictEqual(
+        series2.xAxis.cross.attr('visibility'),
+        'visible',
+        'Hover Series 2: crosshair on xAxis of Series 2 is visible'
+    );
+});