Export zoomRect and make it more configurable (#659)

* Implement zoomRect functions

Normal zooming supports customizing zoom behavior using zoomFunctions, but the drag-to-zoom functionality that's implemented by zoomRect bypasses zoomFunctions and calls updateRange correctly.

I have a custom scale implementation that relies on zoomFunctions, so trying to enable drag-to-zoom causes problems. (Specifically, I'm breaking up the axis into viewports so that I can stack multiple series within this chart - somewhat like this example. The scales for the individual portions of the chart shouldn't be directly zoomed, because their layout is managed by a separate, controlling scale, so their zoomFunctions are no-ops.)

Zooming by rectangle appears to be a distinctly different interface than zooming by percentage and focal point, so it seems reasonable to add a zoomRectFunctions to let scales customize that behavior and cover this use case.

* Expose zoomRect; remove incorrect TypeScript type definitions

To go with adding stronger zoomRect functionality, it makes sense to expose the `zoomRect` function directly.

The TypeScript type definitions said that standalone functions like `zoom` were exported, but these don't actually exist.  Fix that.

* Restore incorrectly deleted type definitions

And properly export zoomRect.

* Further update comments

* Restore type tests

* Fix type

docs/guide/developers.md

@@ -44,7 +44,7 @@ Returns whether the chart has been zoomed or panned - i.e. whether the initial s
 
 ## Custom Scales
 
-You can extend chartjs-plugin-zoom with support for [custom scales](https://www.chartjs.org/docs/latest/developers/axes.html) by using the zoom plugin's `zoomFunctions` and `panFunctions` members. These objects are indexed by scale types (scales' `id` members) and give optional handlers for zoom and pan functionality.
+You can extend chartjs-plugin-zoom with support for [custom scales](https://www.chartjs.org/docs/latest/developers/axes.html) by using the zoom plugin's `zoomFunctions`, `zoomRectFunctions`, and `panFunctions` members. These objects are indexed by scale types (scales' `id` members) and give optional handlers for zoom and pan functionality.
 
 ```js
 import {Scale} from 'chart.js';
@@ -57,17 +57,22 @@ MyScale.id = 'myScale';
 MyScale.defaults = defaultConfigObject;
 
 zoomPlugin.zoomFunctions.myScale = (scale, zoom, center, limits) => false;
+zoomPlugin.zoomRectFunctions.myScale = (scale, from, to, limits) => false;
 zoomPlugin.panFunctions.myScale = (scale, delta, limits) => false;
+// zoomRectFunctions can normally be omitted, since zooming by specific pixel
+// coordinates rarely needs special handling.
 ```
 
-The zoom and pan functions take the following arguments:
+The zoom, zoomRect, and pan functions take the following arguments:
 
 | Name | Type | For | Description
 | ---- | ---- | --- | ----------
 | `scale` | `Scale` | Zoom, Pan | The custom scale instance (usually derived from `Chart.Scale`)
 | `zoom` | `number` | Zoom | The zoom fraction; 1.0 is unzoomed, 0.5 means zoomed in to 50% of the original area, etc.
 | `center` | `{x, y}` | Zoom | Pixel coordinates of the center of the zoom operation. `{x: 0, y: 0}` is the upper left corner of the chart's canvas.
+| `from` | `number` | ZoomRect | Pixel coordinate of the start of the zoomRect operation.
+| `to` | `number` | ZoomRect | Pixel coordinate of the end of the zoomRect operation.
 | `delta` | `number` | Pan | Pixel amount to pan by
 | `limits` | [Limits](./options#limits) | Zoom, Pan | Zoom and pan limits (from chart options)
 
-For examples, see chartjs-plugin-zoom's [default zoomFunctions and panFunctions handling for standard Chart.js axes](https://github.com/chartjs/chartjs-plugin-zoom/blob/v1.0.1/src/scale.types.js#L128).
+For examples, see chartjs-plugin-zoom's [default zoomFunctions, zoomRectFunctions, and panFunctions handling for standard Chart.js axes](https://github.com/chartjs/chartjs-plugin-zoom/blob/v1.0.1/src/scale.types.js#L128).

src/core.js

@@ -1,5 +1,5 @@
 import {each, callback as call, sign, valueOrDefault} from 'chart.js/helpers';
-import {panFunctions, updateRange, zoomFunctions} from './scale.types';
+import {panFunctions, updateRange, zoomFunctions, zoomRectFunctions} from './scale.types';
 import {getState} from './state';
 import {directionEnabled, getEnabledScalesByPoint} from './utils';
 
@@ -43,6 +43,11 @@ function doZoom(scale, amount, center, limits) {
   call(fn, [scale, amount, center, limits]);
 }
 
+function doZoomRect(scale, amount, from, to, limits) {
+  const fn = zoomRectFunctions[scale.type] || zoomRectFunctions.default;
+  call(fn, [scale, amount, from, to, limits]);
+}
+
 function getCenter(chart) {
   const ca = chart.chartArea;
   return {
@@ -80,15 +85,6 @@ export function zoom(chart, amount, transition = 'none') {
   call(zoomOptions.onZoom, [{chart}]);
 }
 
-function getRange(scale, pixel0, pixel1) {
-  const v0 = scale.getValueForPixel(pixel0);
-  const v1 = scale.getValueForPixel(pixel1);
-  return {
-    min: Math.min(v0, v1),
-    max: Math.max(v0, v1)
-  };
-}
-
 export function zoomRect(chart, p0, p1, transition = 'none') {
   const state = getState(chart);
   const {options: {limits, zoom: zoomOptions}} = state;
@@ -100,9 +96,9 @@ export function zoomRect(chart, p0, p1, transition = 'none') {
 
   each(chart.scales, function(scale) {
     if (scale.isHorizontal() && xEnabled) {
-      updateRange(scale, getRange(scale, p0.x, p1.x), limits, true);
+      doZoomRect(scale, p0.x, p1.x, limits);
     } else if (!scale.isHorizontal() && yEnabled) {
-      updateRange(scale, getRange(scale, p0.y, p1.y), limits, true);
+      doZoomRect(scale, p0.y, p1.y, limits);
     }
   });
 

src/index.esm.js

@@ -1,4 +1,4 @@
 import plugin from './plugin';
 
 export default plugin;
-export {pan, zoom, zoomScale, resetZoom} from './core';
+export {pan, zoom, zoomRect, zoomScale, resetZoom} from './core';

src/plugin.js

@@ -1,8 +1,8 @@
 import Hammer from 'hammerjs';
 import {addListeners, computeDragRect, removeListeners} from './handlers';
 import {startHammer, stopHammer} from './hammer';
-import {pan, zoom, resetZoom, zoomScale, getZoomLevel, getInitialScaleBounds, isZoomedOrPanned} from './core';
-import {panFunctions, zoomFunctions} from './scale.types';
+import {pan, zoom, resetZoom, zoomScale, getZoomLevel, getInitialScaleBounds, isZoomedOrPanned, zoomRect} from './core';
+import {panFunctions, zoomFunctions, zoomRectFunctions} from './scale.types';
 import {getState, removeState} from './state';
 import {version} from '../package.json';
 
@@ -53,6 +53,7 @@ export default {
 
     chart.pan = (delta, panScales, transition) => pan(chart, delta, panScales, transition);
     chart.zoom = (args, transition) => zoom(chart, args, transition);
+    chart.zoomRect = (p0, p1, transition) => zoomRect(chart, p0, p1, transition);
     chart.zoomScale = (id, range, transition) => zoomScale(chart, id, range, transition);
     chart.resetZoom = (transition) => resetZoom(chart, transition);
     chart.getZoomLevel = () => getZoomLevel(chart);
@@ -107,6 +108,6 @@ export default {
   },
 
   panFunctions,
-
-  zoomFunctions
+  zoomFunctions,
+  zoomRectFunctions,
 };

src/scale.types.js

@@ -29,6 +29,15 @@ function getLimit(state, scale, scaleLimits, prop, fallback) {
   return valueOrDefault(limit, fallback);
 }
 
+function getRange(scale, pixel0, pixel1) {
+  const v0 = scale.getValueForPixel(pixel0);
+  const v1 = scale.getValueForPixel(pixel1);
+  return {
+    min: Math.min(v0, v1),
+    max: Math.max(v0, v1)
+  };
+}
+
 export function updateRange(scale, {min, max}, limits, zoom = false) {
   const state = getState(scale.chart);
   const {id, axis, options: scaleOpts} = scale;
@@ -72,6 +81,10 @@ function zoomNumericalScale(scale, zoom, center, limits) {
   return updateRange(scale, newRange, limits, true);
 }
 
+function zoomRectNumericalScale(scale, from, to, limits) {
+  updateRange(scale, getRange(scale, from, to), limits, true);
+}
+
 const integerChange = (v) => v === 0 || isNaN(v) ? 0 : v < 0 ? Math.min(Math.round(v), -1) : Math.max(Math.round(v), 1);
 
 function existCategoryFromMaxZoom(scale) {
@@ -158,6 +171,10 @@ export const zoomFunctions = {
   default: zoomNumericalScale,
 };
 
+export const zoomRectFunctions = {
+  default: zoomRectNumericalScale,
+};
+
 export const panFunctions = {
   category: panCategoryScale,
   default: panNumericalScale,

test/specs/api.spec.js

@@ -5,6 +5,7 @@ describe('api', function() {
     expect(typeof chart.pan).toBe('function');
     expect(typeof chart.zoom).toBe('function');
     expect(typeof chart.zoomScale).toBe('function');
+    expect(typeof chart.zoomRect).toBe('function');
     expect(typeof chart.resetZoom).toBe('function');
     expect(typeof chart.getZoomLevel).toBe('function');
     expect(typeof chart.getInitialScaleBounds).toBe('function');

test/specs/module.spec.js

@@ -7,8 +7,9 @@ describe('module', function() {
     expect(window.ChartZoom.id).toBe('zoom');
   });
 
-  it ('should expose zoomFunctions and panFunctions', function() {
+  it ('should expose zoomFunctions, zoomRectFunctions, and panFunctions', function() {
     expect(window.ChartZoom.zoomFunctions instanceof Object).toBe(true);
+    expect(window.ChartZoom.zoomRectFunctions instanceof Object).toBe(true);
     expect(window.ChartZoom.panFunctions instanceof Object).toBe(true);
   });
 

types/index.d.ts

@@ -21,6 +21,7 @@ declare module 'chart.js' {
   interface Chart<TType extends keyof ChartTypeRegistry = keyof ChartTypeRegistry, TData = DistributiveArray<ChartTypeRegistry[TType]['defaultDataPoint']>, TLabel = unknown> {
     pan(pan: PanAmount, scales?: Scale[], mode?: UpdateMode): void;
     zoom(zoom: ZoomAmount, mode?: UpdateMode): void;
+    zoomRect(p0: Point, p1: Point, mode?: UpdateMode): void;
     zoomScale(id: string, range: ScaleRange, mode?: UpdateMode): void;
     resetZoom(mode?: UpdateMode): void;
     getZoomLevel(): number;
@@ -30,6 +31,7 @@ declare module 'chart.js' {
 }
 
 export type ZoomFunction = (scale: Scale, zoom: number, center: Point, limits: LimitOptions) => boolean;
+export type ZoomRectFunction = (scale: Scale, from: number, to: number, limits: LimitOptions) => boolean;
 export type PanFunction = (scale: Scale, delta: number, limits: LimitOptions) => boolean;
 
 type ScaleFunctions<T> = {
@@ -40,13 +42,15 @@ type ScaleFunctions<T> = {
 
 declare const Zoom: Plugin & {
   zoomFunctions: ScaleFunctions<ZoomFunction>;
+  zoomRectFunctions: ScaleFunctions<ZoomRectFunction>;
   panFunctions: ScaleFunctions<PanFunction>;
 };
 
 export default Zoom;
 
 export function pan(chart: Chart, amount: PanAmount, scales?: Scale[], mode?: UpdateMode): void;
 export function zoom(chart: Chart, amount: ZoomAmount, mode?: UpdateMode): void;
+export function zoomRect(chart: Chart, p0: Point, p1: Point, mode?: UpdateMode): void;
 export function zoomScale(chart: Chart, scaleId: string, range: ScaleRange, mode?: UpdateMode): void;
 export function resetZoom(chart: Chart, mode?: UpdateMode): void;
 export function getZoomLevel(chart: Chart): number;