plot().dimensions() returns the chart's dimensions

docs/features/plots.md

@@ -317,3 +317,7 @@ const legend = plot.legend("color"); // render a color legend
 ```
 
 Renders a standalone legend for the scale with the specified *name* (such as *x* or *color*) on the given *plot*, where *plot* is a rendered plot element returned by [plot](#plot), returning a SVG or HTML figure element. This element can then be inserted into the page as described in the [getting started guide](../getting-started.md). If the associated *plot* has no scale with the given *name*, returns undefined. Legends are currently only supported for *color*, *opacity*, and *symbol* scales.
+
+## *plot*.dimensions() {#plot_dimensions}
+
+Returns the dimensions of the chart, an object with the properties marginTop, marginRight, marginBottom, marginLeft, width and height set to their actual values.

src/plot.d.ts

@@ -421,6 +421,18 @@ export interface Plot {
    */
   legend(name: ScaleName, options?: LegendOptions): SVGSVGElement | HTMLElement | undefined;
 
+  /**
+   * Returns the dimensions of the chart.
+   */
+  dimensions(): {
+    marginTop: number;
+    marginRight: number;
+    marginBottom: number;
+    marginLeft: number;
+    width: number;
+    height: number;
+  };
+
   /** For interactive plots, the current value. */
   value?: any;
 }

src/plot.js

@@ -336,6 +336,7 @@ export function plot(options = {}) {
 
   figure.scale = exposeScales(scales.scales);
   figure.legend = exposeLegends(scaleDescriptors, context, options);
+  figure.dimensions = () => ({...dimensions});
 
   const w = consumeWarnings();
   if (w > 0) {

test/plot-test.ts

@@ -6,3 +6,27 @@ it("plot({aspectRatio}) rejects unsupported scale types", () => {
   assert.throws(() => Plot.dot([]).plot({aspectRatio: true, x: {type: "symlog"}}), /^Error: unsupported x scale for aspectRatio: symlog$/); // prettier-ignore
   assert.throws(() => Plot.dot([]).plot({aspectRatio: true, y: {type: "symlog"}}), /^Error: unsupported y scale for aspectRatio: symlog$/); // prettier-ignore
 });
+
+it("plot({}).dimensions() returns the expected values", () => {
+  assert.deepStrictEqual(Plot.dot([]).plot().dimensions(), {
+    marginTop: 20,
+    marginRight: 20,
+    marginBottom: 30,
+    marginLeft: 40,
+    width: 640,
+    height: 400
+  });
+  assert.deepStrictEqual(
+    Plot.dot(["short"], {x: (d, i) => 1 + i, y: (d) => d})
+      .plot()
+      .dimensions(),
+    {
+      marginTop: 20,
+      marginRight: 20,
+      marginBottom: 30,
+      marginLeft: 40,
+      width: 640,
+      height: 80
+    }
+  );
+});