zoom: first pass

src/mark.js

@@ -1,3 +1,4 @@
+import {select} from "d3";
 import {channelDomain, createChannels, valueObject} from "./channel.js";
 import {defined} from "./defined.js";
 import {maybeFacetAnchor} from "./facet.js";
@@ -128,6 +129,24 @@ export class Mark {
     if (context.projection) this.project(channels, values, context);
     return values;
   }
+  // On zoom, a mark can do more interesting things than just applying a
+  // transform; for instance, an axis mark might want to adapt its ticks, and a
+  // dot mark might adjust its radius. By default, though, we just zoom the
+  // zoomable SVG elements (ie everything but clipPath?).
+  zoom(node, transform) {
+    let z = select(node).selectAll(".zoomable");
+    if (z.size() === 0) {
+      z = select(node).append("g").classed("zoomable", true);
+      select(node)
+        .selectChildren("circle,g:not(.zoomable),image,line,path,rect,text")
+        .attr("vector-effect", "non-scaling-stroke")
+        .each(function () {
+          z.append(() => this);
+        });
+    }
+    z.attr("transform", transform);
+    return node;
+  }
 }
 
 export function marks(...marks) {

src/marks/axis.js

@@ -1,4 +1,4 @@
-import {extent, format, timeFormat, utcFormat} from "d3";
+import {extent, format, scaleIdentity, timeFormat, utcFormat} from "d3";
 import {formatDefault} from "../format.js";
 import {marks} from "../mark.js";
 import {radians} from "../math.js";
@@ -129,32 +129,35 @@ function axisKy(
         })
       : null,
     !isNoneish(fill) && label !== null
-      ? text(
-          [],
-          labelOptions({fill, fillOpacity, ...options}, function (data, facets, channels, scales, dimensions) {
-            const scale = scales[k];
-            const {marginTop, marginRight, marginBottom, marginLeft} = (k === "y" && dimensions.inset) || dimensions;
-            const cla = labelAnchor ?? (scale.bandwidth ? "center" : "top");
-            const clo = labelOffset ?? (anchor === "right" ? marginRight : marginLeft) - 3;
-            if (cla === "center") {
-              this.textAnchor = undefined; // middle
-              this.lineAnchor = anchor === "right" ? "bottom" : "top";
-              this.frameAnchor = anchor;
-              this.rotate = -90;
-            } else {
-              this.textAnchor = anchor === "right" ? "end" : "start";
-              this.lineAnchor = cla;
-              this.frameAnchor = `${cla}-${anchor}`;
-              this.rotate = 0;
-            }
-            this.dy = cla === "top" ? 3 - marginTop : cla === "bottom" ? marginBottom - 3 : 0;
-            this.dx = anchor === "right" ? clo : -clo;
-            this.ariaLabel = `${k}-axis label`;
-            return {
-              facets: [[0]],
-              channels: {text: {value: [formatAxisLabel(k, scale, {anchor, label, labelAnchor: cla, labelArrow})]}}
-            };
-          })
+      ? Object.assign(
+          text(
+            [],
+            labelOptions({fill, fillOpacity, ...options}, function (data, facets, channels, scales, dimensions) {
+              const scale = scales[k];
+              const {marginTop, marginRight, marginBottom, marginLeft} = (k === "y" && dimensions.inset) || dimensions;
+              const cla = labelAnchor ?? (scale.bandwidth ? "center" : "top");
+              const clo = labelOffset ?? (anchor === "right" ? marginRight : marginLeft) - 3;
+              if (cla === "center") {
+                this.textAnchor = undefined; // middle
+                this.lineAnchor = anchor === "right" ? "bottom" : "top";
+                this.frameAnchor = anchor;
+                this.rotate = -90;
+              } else {
+                this.textAnchor = anchor === "right" ? "end" : "start";
+                this.lineAnchor = cla;
+                this.frameAnchor = `${cla}-${anchor}`;
+                this.rotate = 0;
+              }
+              this.dy = cla === "top" ? 3 - marginTop : cla === "bottom" ? marginBottom - 3 : 0;
+              this.dx = anchor === "right" ? clo : -clo;
+              this.ariaLabel = `${k}-axis label`;
+              return {
+                facets: [[0]],
+                channels: {text: {value: [formatAxisLabel(k, scale, {anchor, label, labelAnchor: cla, labelArrow})]}}
+              };
+            })
+          ),
+          {zoom: null}
         )
       : null
   );
@@ -230,29 +233,32 @@ function axisKx(
         })
       : null,
     !isNoneish(fill) && label !== null
-      ? text(
-          [],
-          labelOptions({fill, fillOpacity, ...options}, function (data, facets, channels, scales, dimensions) {
-            const scale = scales[k];
-            const {marginTop, marginRight, marginBottom, marginLeft} = (k === "x" && dimensions.inset) || dimensions;
-            const cla = labelAnchor ?? (scale.bandwidth ? "center" : "right");
-            const clo = labelOffset ?? (anchor === "top" ? marginTop : marginBottom) - 3;
-            if (cla === "center") {
-              this.frameAnchor = anchor;
-              this.textAnchor = undefined; // middle
-            } else {
-              this.frameAnchor = `${anchor}-${cla}`;
-              this.textAnchor = cla === "right" ? "end" : "start";
-            }
-            this.lineAnchor = anchor;
-            this.dy = anchor === "top" ? -clo : clo;
-            this.dx = cla === "right" ? marginRight - 3 : cla === "left" ? 3 - marginLeft : 0;
-            this.ariaLabel = `${k}-axis label`;
-            return {
-              facets: [[0]],
-              channels: {text: {value: [formatAxisLabel(k, scale, {anchor, label, labelAnchor: cla, labelArrow})]}}
-            };
-          })
+      ? Object.assign(
+          text(
+            [],
+            labelOptions({fill, fillOpacity, ...options}, function (data, facets, channels, scales, dimensions) {
+              const scale = scales[k];
+              const {marginTop, marginRight, marginBottom, marginLeft} = (k === "x" && dimensions.inset) || dimensions;
+              const cla = labelAnchor ?? (scale.bandwidth ? "center" : "right");
+              const clo = labelOffset ?? (anchor === "top" ? marginTop : marginBottom) - 3;
+              if (cla === "center") {
+                this.frameAnchor = anchor;
+                this.textAnchor = undefined; // middle
+              } else {
+                this.frameAnchor = `${anchor}-${cla}`;
+                this.textAnchor = cla === "right" ? "end" : "start";
+              }
+              this.lineAnchor = anchor;
+              this.dy = anchor === "top" ? -clo : clo;
+              this.dx = cla === "right" ? marginRight - 3 : cla === "left" ? 3 - marginLeft : 0;
+              this.ariaLabel = `${k}-axis label`;
+              return {
+                facets: [[0]],
+                channels: {text: {value: [formatAxisLabel(k, scale, {anchor, label, labelAnchor: cla, labelArrow})]}}
+              };
+            })
+          ),
+          {zoom: null}
         )
       : null
   );
@@ -507,8 +513,10 @@ function labelOptions(
 
 function axisMark(mark, k, ariaLabel, data, options, initialize) {
   let channels;
+  let u;
 
   function axisInitializer(data, facets, _channels, scales, dimensions, context) {
+    u = arguments;
     const initializeFacets = data == null && (k === "fx" || k === "fy");
     const {[k]: scale} = scales;
     if (!scale) throw new Error(`missing scale: ${k}`);
@@ -564,6 +572,24 @@ function axisMark(mark, k, ariaLabel, data, options, initialize) {
     channels = {};
   }
   m.ariaLabel = ariaLabel;
+  m.zoom = function (g, transform) {
+    if (!(k === "x" || k === "y")) return g;
+    const [, , , {[k]: scale}, dimensions, context] = [...u];
+    if (scale.bandwidth) return g; // TODO ordinal scales?
+    const scale2 = transform[k === "x" ? "rescaleX" : "rescaleY"](scale ?? scaleIdentity());
+    const ticks = scale2.ticks();
+    g.replaceWith(
+      (g = m.render.call(
+        m,
+        ticks.map((d, i) => i),
+        {[k]: scale2},
+        {[k]: ticks.map(scale2), text: ticks},
+        dimensions,
+        context
+      ))
+    );
+    return g;
+  };
   return m;
 }
 

src/marks/dot.js

@@ -1,4 +1,4 @@
-import {pathRound as path, symbolCircle} from "d3";
+import {pathRound as path, select, symbolCircle} from "d3";
 import {create} from "../context.js";
 import {negative, positive} from "../defined.js";
 import {Mark} from "../mark.js";
@@ -128,6 +128,15 @@ export class Dot extends Mark {
       )
       .node();
   }
+  zoom(node, transform, values) {
+    const a = 1 / Math.sqrt(transform.k);
+    select(node)
+      .attr("transform", transform)
+      .selectAll("circle")
+      .attr("vector-effect", "non-scaling-stroke")
+      .attr("r", values.r ? (i) => a * values.r[i] : this.r * a);
+    return node;
+  }
 }
 
 export function dot(data, {x, y, ...options} = {}) {

src/plot.js

@@ -1,4 +1,4 @@
-import {creator, select} from "d3";
+import {creator, select, zoom as zoomer} from "d3";
 import {createChannel, inferChannelScale} from "./channel.js";
 import {createContext} from "./context.js";
 import {createDimensions} from "./dimensions.js";
@@ -20,7 +20,7 @@ import {initializer} from "./transforms/basic.js";
 import {consumeWarnings, warn} from "./warnings.js";
 
 export function plot(options = {}) {
-  const {facet, style, caption, ariaLabel, ariaDescription} = options;
+  const {facet, style, caption, ariaLabel, ariaDescription, zoom} = options;
 
   // className for inline styles
   const className = maybeClassName(options.className);
@@ -272,6 +272,7 @@ export function plot(options = {}) {
     .call(applyInlineStyles, style);
 
   // Render marks.
+  const nodesByMark = new Map();
   for (const mark of marks) {
     const {channels, values, facets: indexes} = stateByMark.get(mark);
 
@@ -285,6 +286,7 @@ export function plot(options = {}) {
       }
       const node = mark.render(index, scales, values, superdimensions, context);
       if (node == null) continue;
+      nodesByMark.set(mark, node);
       svg.appendChild(node);
     }
 
@@ -337,6 +339,25 @@ export function plot(options = {}) {
   figure.scale = exposeScales(scaleDescriptors);
   figure.legend = exposeLegends(scaleDescriptors, context, options);
 
+  if (zoom || true) {
+    select(svg).call(
+      zoomer().on("start zoom end", ({transform}) => {
+        // todo also opt-out when a scale is collapsed.
+        if (scales.y?.bandwidth || zoom === "x") {
+          transform.toString = () => `translate(${transform.x},${0})scale(${transform.k},1)`;
+          transform.rescaleY = (y) => y;
+        }
+        if (scales.x?.bandwidth || zoom === "y") {
+          transform.toString = () => `translate(${0},${transform.y})scale(1,${transform.k})`;
+          transform.rescaleX = (x) => x;
+        }
+        for (const [mark, node] of nodesByMark) {
+          if (mark.zoom != null) nodesByMark.set(mark, mark.zoom(node, transform, stateByMark.get(mark).values));
+        }
+      })
+    );
+  }
+
   const w = consumeWarnings();
   if (w > 0) {
     select(svg)