feat: allow custom tooltip formatting

build/vega-lite-schema.json

@@ -7765,6 +7765,10 @@
           "$ref": "#/definitions/TitleConfig",
           "description": "Title configuration, which determines default properties for all [titles](https://vega.github.io/vega-lite/docs/title.html). For a full list of title configuration options, please see the [corresponding section of the title documentation](https://vega.github.io/vega-lite/docs/title.html#config)."
         },
+        "tooltipFormat": {
+          "$ref": "#/definitions/FormatConfig",
+          "description": "Define [custom format configuration](https://vega.github.io/vega-lite/docs/config.html#format) for tooltips. If unspecified, default format config will be applied."
+        },
         "trail": {
           "$ref": "#/definitions/LineConfig",
           "description": "Trail-Specific Config"
@@ -10851,6 +10855,36 @@
         "number"
       ]
     },
+    "FormatConfig": {
+      "additionalProperties": false,
+      "properties": {
+        "normalizedNumberFormat": {
+          "description": "If normalizedNumberFormatType is not specified, D3 number format for axis labels, text marks, and tooltips of normalized stacked fields (fields with `stack: \"normalize\"`). For example `\"s\"` for SI units. Use [D3's number format pattern](https://github.com/d3/d3-format#locale_format).\n\nIf `config.normalizedNumberFormatType` is specified and `config.customFormatTypes` is `true`, this value will be passed as `format` alongside `datum.value` to the `config.numberFormatType` function. __Default value:__ `%`",
+          "type": "string"
+        },
+        "normalizedNumberFormatType": {
+          "description": "[Custom format type](https://vega.github.io/vega-lite/docs/config.html#custom-format-type) for `config.normalizedNumberFormat`.\n\n__Default value:__ `undefined` -- This is equilvalent to call D3-format, which is exposed as [`format` in Vega-Expression](https://vega.github.io/vega/docs/expressions/#format). __Note:__ You must also set `customFormatTypes` to `true` to use this feature.",
+          "type": "string"
+        },
+        "numberFormat": {
+          "description": "If numberFormatType is not specified, D3 number format for guide labels, text marks, and tooltips of non-normalized fields (fields *without* `stack: \"normalize\"`). For example `\"s\"` for SI units. Use [D3's number format pattern](https://github.com/d3/d3-format#locale_format).\n\nIf `config.numberFormatType` is specified and `config.customFormatTypes` is `true`, this value will be passed as `format` alongside `datum.value` to the `config.numberFormatType` function.",
+          "type": "string"
+        },
+        "numberFormatType": {
+          "description": "[Custom format type](https://vega.github.io/vega-lite/docs/config.html#custom-format-type) for `config.numberFormat`.\n\n__Default value:__ `undefined` -- This is equilvalent to call D3-format, which is exposed as [`format` in Vega-Expression](https://vega.github.io/vega/docs/expressions/#format). __Note:__ You must also set `customFormatTypes` to `true` to use this feature.",
+          "type": "string"
+        },
+        "timeFormat": {
+          "description": "Default time format for raw time values (without time units) in text marks, legend labels and header labels.\n\n__Default value:__ `\"%b %d, %Y\"` __Note:__ Axes automatically determine the format for each label automatically so this config does not affect axes.",
+          "type": "string"
+        },
+        "timeFormatType": {
+          "description": "[Custom format type](https://vega.github.io/vega-lite/docs/config.html#custom-format-type) for `config.timeFormat`.\n\n__Default value:__ `undefined` -- This is equilvalent to call D3-time-format, which is exposed as [`timeFormat` in Vega-Expression](https://vega.github.io/vega/docs/expressions/#timeFormat). __Note:__ You must also set `customFormatTypes` to `true` and there must *not* be a `timeUnit` defined to use this feature.",
+          "type": "string"
+        }
+      },
+      "type": "object"
+    },
     "Generator": {
       "anyOf": [
         {

examples/compiled/config_numberFormatType_tooltip.vg.json

@@ -0,0 +1,126 @@
+{
+  "$schema": "https://vega.github.io/schema/vega/v5.json",
+  "description": "Testing global number formatting config",
+  "background": "white",
+  "padding": 5,
+  "width": 150,
+  "height": 150,
+  "style": "cell",
+  "data": [
+    {
+      "name": "source_0",
+      "url": "data/cars.json",
+      "format": {"type": "json", "parse": {"Year": "date"}},
+      "transform": [
+        {
+          "type": "aggregate",
+          "groupby": ["Year"],
+          "ops": ["average"],
+          "fields": ["Miles_per_Gallon"],
+          "as": ["average_Miles_per_Gallon"]
+        },
+        {
+          "type": "filter",
+          "expr": "(isDate(datum[\"Year\"]) || (isValid(datum[\"Year\"]) && isFinite(+datum[\"Year\"]))) && isValid(datum[\"average_Miles_per_Gallon\"]) && isFinite(+datum[\"average_Miles_per_Gallon\"])"
+        }
+      ]
+    }
+  ],
+  "marks": [
+    {
+      "name": "marks",
+      "type": "rect",
+      "style": ["bar"],
+      "from": {"data": "source_0"},
+      "encode": {
+        "update": {
+          "tooltip": {
+            "signal": "{\"Year\": timeFormat(datum[\"Year\"], '%b %d, %Y'), \"Average of Miles_per_Gallon\": format(datum[\"average_Miles_per_Gallon\"], \".8f\")}"
+          },
+          "fill": {"value": "#4c78a8"},
+          "ariaRoleDescription": {"value": "bar"},
+          "description": {
+            "signal": "\"Year: \" + (timeFormat(datum[\"Year\"], '%b %d, %Y')) + \"; Average of Miles_per_Gallon: \" + (format(datum[\"average_Miles_per_Gallon\"], \".8f\"))"
+          },
+          "xc": {"scale": "x", "field": "Year"},
+          "width": {"value": 5},
+          "y": {"scale": "y", "field": "average_Miles_per_Gallon"},
+          "y2": {"scale": "y", "value": 0}
+        }
+      }
+    }
+  ],
+  "scales": [
+    {
+      "name": "x",
+      "type": "time",
+      "domain": {"data": "source_0", "field": "Year"},
+      "range": [0, {"signal": "width"}],
+      "padding": 5
+    },
+    {
+      "name": "y",
+      "type": "linear",
+      "domain": {"data": "source_0", "field": "average_Miles_per_Gallon"},
+      "range": [{"signal": "height"}, 0],
+      "nice": true,
+      "zero": true
+    }
+  ],
+  "axes": [
+    {
+      "scale": "x",
+      "orient": "bottom",
+      "gridScale": "y",
+      "grid": true,
+      "tickCount": {"signal": "ceil(width/40)"},
+      "domain": false,
+      "labels": false,
+      "aria": false,
+      "maxExtent": 0,
+      "minExtent": 0,
+      "ticks": false,
+      "zindex": 0
+    },
+    {
+      "scale": "y",
+      "orient": "left",
+      "gridScale": "x",
+      "grid": true,
+      "tickCount": {"signal": "ceil(height/40)"},
+      "tickMinStep": 1,
+      "domain": false,
+      "labels": false,
+      "aria": false,
+      "maxExtent": 0,
+      "minExtent": 0,
+      "ticks": false,
+      "zindex": 0
+    },
+    {
+      "scale": "x",
+      "orient": "bottom",
+      "grid": false,
+      "title": "Year",
+      "labelFlush": true,
+      "labelOverlap": true,
+      "tickCount": {"signal": "ceil(width/40)"},
+      "zindex": 0
+    },
+    {
+      "scale": "y",
+      "orient": "left",
+      "grid": false,
+      "title": "Average of Miles_per_Gallon",
+      "format": "d",
+      "labelOverlap": true,
+      "tickCount": {"signal": "ceil(height/40)"},
+      "tickMinStep": 1,
+      "zindex": 0
+    }
+  ],
+  "config": {
+    "tooltipFormat": {"numberFormat": ".8f"},
+    "customFormatTypes": true
+  }
+}

examples/specs/config_numberFormatType_tooltip.vl.json

@@ -0,0 +1,19 @@
+{
+  "$schema": "https://vega.github.io/schema/vega-lite/v5.json",
+  "description": "Testing global number formatting config",
+  "width": 150,
+  "height": 150,
+  "data": {"url": "data/cars.json"},
+  "mark": {"type": "bar", "tooltip": true},
+  "encoding": {
+    "x": {"field": "Year", "type": "temporal"},
+    "y": {"field": "Miles_per_Gallon", "type": "quantitative", "aggregate": "average"}
+  },
+  "config": {
+    "tooltipFormat": {
+      "numberFormat": ".8f"
+    },
+    "numberFormat": "d",
+    "customFormatTypes": true
+  }
+}

site/docs/config.md

@@ -44,13 +44,13 @@ The rest of this page outlines different types of config properties:
 
 A Vega-Lite `config` object can have the following top-level properties:
 
-{% include table.html props="autosize,background,countTitle,fieldTitle,font,lineBreak,padding" source="Config" %}
+{% include table.html props="autosize,background,countTitle,fieldTitle,font,lineBreak,padding,tooltipFormat" source="Config" %}
 
 {:#format}
 
 ## Format Configuration
 
-These config properties define the default number and time formats for text marks as well as axes, headers, and legends:
+These config properties define the default number and time formats for text marks as well as axes, headers, tooltip, and legends:
 
 {% include table.html props="numberFormat,numberFormatType,normalizedNumberFormat,normalizedNumberFormatType,timeFormat,timeFormatType,customFormatTypes" source="Config" %}
 
@@ -69,7 +69,7 @@ vega.expressionFunction('customFormatA', function(datum, params) {
 });
 ```
 
-2. Setting the `customFormatTypes` config to `true`.
+(2) Setting the `customFormatTypes` config to `true`.
 
 ```js
 {
@@ -78,7 +78,7 @@ vega.expressionFunction('customFormatA', function(datum, params) {
 }
 ```
 
-3. You can then use this custom format function with `format` and `formatType` properties in text encodings and guides (axis/legend/header).
+(3) You can then use this custom format function with `format` and `formatType` properties in text encodings and guides (axis/legend/header).
 
 ```js
 {
@@ -87,6 +87,12 @@ vega.expressionFunction('customFormatA', function(datum, params) {
 }
 ```
 
+### Customize Formatter for Tooltips only
+
+Since tooltips have more screen estate and less chance of collisions, sometimes it is desirable to have a truncated format in a visualization, with a longer format in the tooltip. For example, in the visualization below, we want the y-axis to have the format `d` so it does not have a decimal point, so as not to have incredibly long labels, but on the tooltip it has the longer `.8f`. To achieve this specificity, one can add a `tooltipFormat` prop to their config that conforms to the [FormatConfig](#format) type.
+
+<span class="vl-example" data-name="config_numberFormatType_tooltip"></span>
+
 {:#axis-config}
 
 ## Guide Configurations

src/compile/mark/encode/tooltip.ts

@@ -72,6 +72,7 @@ export function tooltipData(
   config: Config,
   {reactiveGeom}: {reactiveGeom?: boolean} = {}
 ) {
+  const formatConfig = {...config, ...config.tooltipFormat};
   const toSkip = {};
   const expr = reactiveGeom ? 'datum.datum' : 'datum';
   const tuples: {channel: Channel; key: string; value: string}[] = [];
@@ -86,7 +87,7 @@ export function tooltipData(
           type: (encoding[mainChannel] as TypedFieldDef<any>).type // for secondary field def, copy type from main channel
         };
 
-    const title = fieldDef.title || defaultTitle(fieldDef, config);
+    const title = fieldDef.title || defaultTitle(fieldDef, formatConfig);
     const key = array(title).join(', ');
 
     let value: string;
@@ -99,7 +100,7 @@ export function tooltipData(
         const startField = vgField(fieldDef, {expr});
         const endField = vgField(fieldDef2, {expr});
         const {format, formatType} = getFormatMixins(fieldDef);
-        value = binFormatExpression(startField, endField, format, formatType, config);
+        value = binFormatExpression(startField, endField, format, formatType, formatConfig);
         toSkip[channel2] = true;
       }
     }
@@ -116,12 +117,12 @@ export function tooltipData(
         format,
         formatType,
         expr,
-        config,
+        config: formatConfig,
         normalizeStack: true
       }).signal;
     }
 
-    value ??= textRef(fieldDef, config, expr).signal;
+    value ??= textRef(fieldDef, formatConfig, expr).signal;
 
     tuples.push({channel, key, value});
   }