add unifiedhovertemplate

Author: archmoj

src/components/fx/hover.js

@@ -1211,10 +1211,22 @@ function createHoverText(hoverData, opts) {
         // mock legend
         var hoverlabel = fullLayout.hoverlabel;
         var font = hoverlabel.font;
+
+        var unifiedhovertemplate = (
+            (hovermode === 'y unified') ?
+                groupedHoverData[0]?.xa :
+                groupedHoverData[0]?.ya
+            ).unifiedhovertemplate;
+
+        var mainText = Lib.hovertemplateString(unifiedhovertemplate, {}, fullLayout._d3locale, {
+            x: hovermode === 'y unified' ? t0 : undefined,
+            y: hovermode === 'x unified' ? t0 : undefined,
+        });
+
         var mockLayoutIn = {
             showlegend: true,
             legend: {
-                title: {text: t0, font: font},
+                title: {text: mainText, font: font},
                 font: font,
                 bgcolor: hoverlabel.bgcolor,
                 bordercolor: hoverlabel.bordercolor,

src/plots/cartesian/axis_defaults.js

@@ -100,7 +100,10 @@ module.exports = function handleAxisDefaults(containerIn, containerOut, coerce,
 
     handleCategoryOrderDefaults(containerIn, containerOut, coerce, options);
 
-    if(axType !== 'category' && !options.noHover) coerce('hoverformat');
+    if(!options.noHover) {
+        if(axType !== 'category') coerce('hoverformat');
+        coerce('unifiedhovertemplate');
+    }
 
     var dfltColor = coerce('color');
     // if axis.color was provided, use it for fonts too; otherwise,

src/plots/cartesian/layout_attributes.js

@@ -5,6 +5,7 @@ var colorAttrs = require('../../components/color/attributes');
 var dash = require('../../components/drawing/attributes').dash;
 var extendFlat = require('../../lib/extend').extendFlat;
 var templatedArray = require('../../plot_api/plot_template').templatedArray;
+var hovertemplateAttrs = require('../../plots/template_attributes').hovertemplateAttrs;
 var descriptionWithDates = require('../../plots/cartesian/axis_format_attributes').descriptionWithDates;
 
 var ONEDAY = require('../../constants/numerical').ONEDAY;
@@ -974,6 +975,9 @@ module.exports = {
         editType: 'none',
         description: descriptionWithDates('hover text')
     },
+    unifiedhovertemplate: hovertemplateAttrs({
+        noSupportOther: true
+    }),
     // lines and grids
     showline: {
         valType: 'boolean',

src/plots/template_attributes.js

@@ -71,7 +71,9 @@ exports.hovertemplateAttrs = function(opts, extra) {
         description: [
             'Template string used for rendering the information that appear on hover box.',
             'Note that this will override `hoverinfo`.',
-            templateFormatStringDescription({supportOther: true}),
+            templateFormatStringDescription({
+                supportOther: opts.noSupportOther ? false : true
+            }),
             'The variables available in `hovertemplate` are the ones emitted as event data described at this link https://plotly.com/javascript/plotlyjs-events/#event-data.',
             'Additionally, every attributes that can be specified per-point (the ones that are `arrayOk: true`) are available.',
             descPart,