[vx-bounds] add package with 'withBoundingRects()' HOC and tests

packages/vx-bounds/.babelrc

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+{
+  "presets": ["es2015", "react", "stage-0"],
+  "plugins": [],
+  "env": {
+    "development": {
+      "plugins": [
+        ["react-transform", {
+          "transforms": [{
+            "transform": "react-transform-hmr",
+            "imports": ["react"],
+            "locals": ["module"]
+          }]
+        }],
+        "transform-runtime",
+        "transform-decorators-legacy"
+      ]
+    }
+  }
+}

packages/vx-bounds/Makefile

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+include node_modules/react-fatigue-dev/Makefile

packages/vx-bounds/Readme.md

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+# @vx/bounds
+
+```
+npm install --save @vx/bounds
+```
+
+### `withBoundingRects` HOC
+It's often useful to determine whether elements (e.g., tooltips) overflow the bounds of their parent container and adjust positioning accordingly. The `withBoundingRects` higher-order component is meant to simplify this computation by passing in a component's bounding rect as well as its _parent's_ bounding rect.
+
+
+### Example usage
+Example usage with a `<Tooltip />` component
+
+```javascript
+import React from 'react';
+import PropTypes from 'prop-types';
+import { withBoundingRects, withBoundingRectsProps } from '@vx/bounds';
+
+const propTypes = {
+  ...withBoundingRectsProps,
+  left: PropTypes.number.isRequired,
+  top: PropTypes.number.isRequired,
+  children: PropTypes.node,
+};
+
+const defaultProps = {
+  children: null,
+};
+
+function Tooltip({
+  left: initialLeft,
+  top: initialTop,
+  rect,
+  parentRect,
+  children,
+}) {
+  let left = initialLeft;
+  let top = initialTop;
+
+  if (rect && parentRect) {
+    left = rect.right > parentRect.right ? (left - rect.width) : left;
+    top = rect.bottom > parentRect.bottom ? (top - rect.height) : top;
+  }
+
+  return (
+    <div style={{ top, left, ...myTheme }}>
+      {children}
+    </div>
+  );
+}
+
+Tooltip.propTypes = propTypes;
+Tooltip.defaultProps = defaultProps;
+
+export default withBoundingRects(Tooltip);
+```

packages/vx-bounds/package.json

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+{
+  "name": "@vx/bounds",
+  "version": "0.0.0",
+  "description": "Utilities to make your life with bounding boxes better",
+  "main": "build/index.js",
+  "scripts": {
+    "build": "make build SRC=./src",
+    "prepublish": "make build SRC=./src",
+    "test": "jest"
+  },
+  "files": [
+    "build"
+  ],
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/hshoff/vx.git"
+  },
+  "keywords": [
+    "vx",
+    "react",
+    "visualizations",
+    "charts"
+  ],
+  "author": "Chris Williams @williaster",
+  "license": "MIT",
+  "bugs": {
+    "url": "https://github.com/hshoff/vx/issues"
+  },
+  "homepage": "https://github.com/hshoff/vx#readme",
+  "publishConfig": {
+    "access": "public"
+  },
+  "devDependencies": {
+    "babel-jest": "^20.0.3",
+    "enzyme": "^2.8.2",
+    "jest": "^20.0.3",
+    "react": "^15.0.0 || 15.x",
+    "react-addons-test-utils": "^15.4.2",
+    "react-fatigue-dev": "github:tj/react-fatigue-dev",
+    "react-tools": "^0.10.0",
+    "regenerator-runtime": "^0.10.5"
+  },
+  "dependencies": {
+    "prop-types": "^15.5.10",
+    "react-dom": "^15.0.0 || 15.x"
+  },
+  "peerDependencies": {
+    "react": "^15.0.0 || 15.x"
+  }
+}

packages/vx-bounds/src/enhancers/withBoundingRects.js

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+/* eslint react/no-did-mount-set-state: 0, react/no-find-dom-node: 0 */
+import React from 'react';
+import ReactDOM from 'react-dom';
+import PropTypes from 'prop-types';
+
+const emptyRect = {
+  top: 0,
+  right: 0,
+  bottom: 0,
+  left: 0,
+  width: 0,
+  height: 0,
+};
+
+const rectShape = PropTypes.shape({
+  top: PropTypes.number.isRequired,
+  right: PropTypes.number.isRequired,
+  bottom: PropTypes.number.isRequired,
+  left: PropTypes.number.isRequired,
+  width: PropTypes.number.isRequired,
+  height: PropTypes.number.isRequired,
+});
+
+export const withBoundingRectsProps = {
+  getRects: PropTypes.func,
+  rect: rectShape,
+  parentRect: rectShape,
+};
+
+export default function withBoundingRects(BaseComponent) {
+  class WrappedComponent extends React.PureComponent {
+    constructor(props) {
+      super(props);
+      this.state = {
+        rect: undefined,
+        parentRect: undefined,
+      };
+      this.getRects = this.getRects.bind(this);
+    }
+
+    componentDidMount() {
+      this.node = ReactDOM.findDOMNode(this);
+      this.setState(this.getRects());
+    }
+
+    getRects() {
+      if (!this.node) return this.state;
+
+      const node = this.node;
+      const parentNode = this.node.parentNode;
+
+      const rect = node.getBoundingClientRect
+        ? node.getBoundingClientRect()
+        : emptyRect;
+
+      const parentRect = parentNode && parentNode.getBoundingClientRect
+        ? parentNode.getBoundingClientRect()
+        : emptyRect;
+
+      return { rect, parentRect };
+    }
+
+    render() {
+      return (
+        <BaseComponent
+          getRects={this.getRects}
+          {...this.state}
+          {...this.props}
+        />
+      );
+    }
+  }
+
+  WrappedComponent.propTypes = BaseComponent.propTypes;
+  WrappedComponent.defaultProps = BaseComponent.defaultProps;
+  WrappedComponent.displayName = `withBoundingRects(${BaseComponent.displayName || ''})`;
+
+  return WrappedComponent;
+}

packages/vx-bounds/src/index.js

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+export { default as withBoundingRects, withBoundingRectsProps } from './enhancers/withBoundingRects';

packages/vx-bounds/test/withBoundingRects.test.js

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+import React from 'react';
+import { mount } from 'enzyme';
+
+import { withBoundingRects, withBoundingRectsProps } from '../src/';
+
+const expectedRectShape = expect.objectContaining({
+  top: expect.any(Number),
+  right: expect.any(Number),
+  bottom: expect.any(Number),
+  left: expect.any(Number),
+  width: expect.any(Number),
+  height: expect.any(Number),
+});
+
+describe('withBoundingRects()', () => {
+  beforeAll(() => { // mock getBoundingClientRect
+    Element.prototype.getBoundingClientRect = jest.fn(() => ({
+      width: 100,
+      height: 100,
+      top: 0,
+      left: 0,
+      bottom: 0,
+      right: 0,
+    }));
+  });
+
+  function Component() {
+    return <div />;
+  }
+
+  test('it should be defined', () => {
+    expect(withBoundingRects).toBeDefined();
+  });
+
+  test('it should pass rect, parentRect, and getRect props to the wrapped component', () => {
+    const HOC = withBoundingRects(Component);
+    const wrapper = mount(<HOC />);
+    const RenderedComponent = wrapper.find(Component);
+
+    expect(Element.prototype.getBoundingClientRect).toHaveBeenCalled();
+    expect(RenderedComponent.prop('rect')).toEqual(expectedRectShape);
+    expect(RenderedComponent.prop('parentRect')).toEqual(expectedRectShape);
+    expect(typeof RenderedComponent.prop('getRects')).toBe('function');
+  });
+
+  test('it should pass additional props to the wrapped component', () => {
+    const HOC = withBoundingRects(Component);
+    const wrapper = mount(<HOC bananas="are yellow" />);
+    const RenderedComponent = wrapper.find(Component);
+    expect(RenderedComponent.prop('bananas')).toBe('are yellow');
+  });
+});
+
+describe('withBoundingRectsProps', () => {
+  test('it should be defined', () => {
+    expect(withBoundingRectsProps).toBeDefined();
+  });
+});