Add className option for marks

docs/features/marks.md

@@ -482,6 +482,7 @@ All marks support the following style options:
 * **dx** - horizontal offset (in pixels; defaults to 0)
 * **dy** - vertical offset (in pixels; defaults to 0)
 * **target** - link target (e.g., “_blank” for a new window); for use with the **href** channel
+* **className** - the [class attribute](https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/class), if any (defaults to null) <VersionBadge pr="1098" />
 * **ariaDescription** - a textual description of the mark’s contents
 * **ariaHidden** - if true, hide this content from the accessibility tree
 * **pointerEvents** - the [pointer events](https://developer.mozilla.org/en-US/docs/Web/CSS/pointer-events) (*e.g.*, *none*)

src/mark.d.ts

@@ -239,6 +239,13 @@ export interface MarkOptions {
    */
   marginLeft?: number;
 
+  /**
+   * The [class attribute][1]; a constant string.
+   *
+   * [1]: https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/class
+   */
+  className?: string;
+
   /**
    * The [aria-description][1]; a constant textual description.
    *

src/mark.js

@@ -4,7 +4,7 @@ import {maybeFacetAnchor} from "./facet.js";
 import {maybeClip, maybeNamed, maybeValue} from "./options.js";
 import {arrayify, isDomainSort, isObject, isOptions, keyword, range, singleton} from "./options.js";
 import {project} from "./projection.js";
-import {styles} from "./style.js";
+import {maybeClassName, styles} from "./style.js";
 import {basic, initializer} from "./transforms/basic.js";
 
 export class Mark {
@@ -22,6 +22,7 @@ export class Mark {
       marginRight = margin,
       marginBottom = margin,
       marginLeft = margin,
+      className,
       clip = defaults?.clip,
       channels: extraChannels,
       tip,
@@ -71,6 +72,7 @@ export class Mark {
     this.marginLeft = +marginLeft;
     this.clip = maybeClip(clip);
     this.tip = maybeTip(tip);
+    this.className = className ? maybeClassName(className) : null;
     // Super-faceting currently disallow position channels; in the future, we
     // could allow position to be specified in fx and fy in addition to (or
     // instead of) x and y.

src/style.js

@@ -348,6 +348,7 @@ function applyClip(selection, mark, dimensions, context) {
 // Note: may mutate selection.node!
 export function applyIndirectStyles(selection, mark, dimensions, context) {
   applyClip(selection, mark, dimensions, context);
+  applyAttr(selection, "class", mark.className);
   applyAttr(selection, "fill", mark.fill);
   applyAttr(selection, "fill-opacity", mark.fillOpacity);
   applyAttr(selection, "stroke", mark.stroke);

test/plots/class-name.ts

@@ -0,0 +1,20 @@
+import * as Plot from "@observablehq/plot";
+import * as d3 from "d3";
+
+export async function classNameOnMarks() {
+  const sales = await d3.csv("data/fruit-sales.csv", d3.autoType);
+  return Plot.plot({
+    marginLeft: 50,
+    y: {
+      label: null,
+      reverse: true
+    },
+    marks: [
+      Plot.barX(
+        sales,
+        Plot.groupY({x: "sum"}, {x: "units", y: "fruit", sort: {y: "x", reverse: true}, className: "fruitbars"})
+      ),
+      Plot.ruleX([0])
+    ]
+  });
+}

test/plots/index.ts

@@ -51,6 +51,7 @@ export * from "./cars-mpg.js";
 export * from "./cars-parcoords.js";
 export * from "./channel-domain.js";
 export * from "./clamp.js";
+export * from "./class-name.js";
 export * from "./collapsed-histogram.js";
 export * from "./color-piecewise.js";
 export * from "./country-centroids.js";