do not rotate single labels in 'closest'

... and if the corresponding trace is 'horizontal'

Author: etpinard

src/components/fx/hover.js

@@ -237,8 +237,8 @@ function _hover(gd, evt, subplot, noHoverEvent) {
         vLinePoint: null
     };
 
-    // does subplot have one (or more) horizontal traces,
-    // (to determine whether we rotate the labels or not)
+    // does subplot have one (or more) horizontal traces?
+    // This is used to determine whether we rotate the labels or not
     var hasOneHorizontalTrace = false;
 
     // Figure out what we're hovering on:
@@ -590,7 +590,7 @@ function _hover(gd, evt, subplot, noHoverEvent) {
 
     var rotateLabels = (
         (hovermode === 'y' && (searchData.length > 1 || hoverData.length > 1)) ||
-        (hovermode === 'closest' && hasOneHorizontalTrace)
+        (hovermode === 'closest' && hasOneHorizontalTrace && hoverData.length > 1)
     );
 
     var bgColor = Color.combine(

test/jasmine/tests/hover_label_test.js

@@ -2470,6 +2470,113 @@ describe('hover distance', function() {
     });
 });
 
+describe('hover label rotation:', function() {
+    var gd;
+
+    function _hover(gd, opts) {
+        Fx.hover(gd, opts);
+        Lib.clearThrottle();
+    }
+
+    describe('when a single pt is picked', function() {
+        afterAll(destroyGraphDiv);
+
+        beforeAll(function(done) {
+            gd = createGraphDiv();
+
+            Plotly.plot(gd, [{
+                type: 'bar',
+                orientation: 'h',
+                y: [0, 1, 2],
+                x: [1, 2, 1]
+            }, {
+                type: 'bar',
+                orientation: 'h',
+                y: [3, 4, 5],
+                x: [1, 2, 1]
+            }], {
+                hovermode: 'y'
+            })
+            .catch(failTest)
+            .then(done);
+        });
+
+        it('should rotate labels under *hovermode:y*', function() {
+            _hover(gd, { xval: 2, yval: 1 });
+            assertHoverLabelContent({
+                nums: '2',
+                name: 'trace 0',
+                axis: '1',
+                // N.B. could be changed to be made consistent with 'closest'
+                isRotated: true
+            });
+        });
+
+        it('should not rotate labels under *hovermode:closest*', function(done) {
+            Plotly.relayout(gd, 'hovermode', 'closest').then(function() {
+                _hover(gd, { xval: 1.9, yval: 1 });
+                assertHoverLabelContent({
+                    nums: '(2, 1)',
+                    name: 'trace 0',
+                    axis: '',
+                    isRotated: false
+                });
+            })
+            .catch(failTest)
+            .then(done);
+        });
+    });
+
+    describe('when mulitple pts are picked', function() {
+        afterAll(destroyGraphDiv);
+
+        beforeAll(function(done) {
+            gd = createGraphDiv();
+
+            Plotly.plot(gd, [{
+                type: 'bar',
+                orientation: 'h',
+                y: [0, 1, 2],
+                x: [1, 2, 1]
+            }, {
+                type: 'bar',
+                orientation: 'h',
+                y: [0, 1, 2],
+                x: [1, 2, 1]
+            }], {
+                hovermode: 'y'
+            })
+            .catch(failTest)
+            .then(done);
+        });
+
+        it('should rotate labels under *hovermode:y*', function() {
+            _hover(gd, { xval: 2, yval: 1 });
+            assertHoverLabelContent({
+                nums: ['2', '2'],
+                name: ['trace 0', 'trace 1'],
+                axis: '1',
+                isRotated: true
+            });
+        });
+
+        it('should not rotate labels under *hovermode:closest*', function(done) {
+            Plotly.relayout(gd, 'hovermode', 'closest').then(function() {
+                _hover(gd, { xval: 1.9, yval: 1 });
+                assertHoverLabelContent({
+                    nums: '(2, 1)',
+                    // N.B. only showing the 'top' trace
+                    name: 'trace 1',
+                    axis: '',
+                    isRotated: false
+                });
+            })
+            .catch(failTest)
+            .then(done);
+        });
+    });
+});
+
 describe('hovermode defaults to', function() {
     var gd;
 

test/jasmine/tests/violin_test.js

@@ -476,6 +476,19 @@ describe('Test violin hover:', function() {
         name: ['radishes', '', '', '', ''],
         hOrder: [4, 3, 0, 2, 1],
         isRotated: true
+    }, {
+        desc: 'hovering over single pt on horizontal violin should not rotate labels',
+        mock: require('@mocks/violin_old-faithful.json'),
+        patch: function(fig) {
+            fig.data[0].x = fig.data[0].y;
+            delete fig.data[0].y;
+            fig.layout = {hovermode: 'closest'};
+            return fig;
+        },
+        pos: [539, 293],
+        nums: '(96, Old Faithful)',
+        name: '',
+        isRotated: false
     }]
     .forEach(function(specs) {
         it('should generate correct hover labels ' + specs.desc, function(done) {