Popover: Refactor to render using React portals

components/popover/README.md

@@ -0,0 +1,53 @@
+Popover
+=======
+
+Popover is a React component to render a floating content modal. It is similar in purpose to a tooltip, but renders content of any sort, not only simple text. It anchors itself to its parent node, optionally by a specified direction. If the popover exceeds the bounds of the page in the direction it opens, its position will be flipped automatically.
+
+## Usage
+
+Render a Popover within the parent to which it should anchor:
+
+```jsx
+import { Popover } from '@wordpress/components';
+
+function ToggleButton( { isVisible, toggleVisible } ) {
+	return (
+		<button onClick={ toggleVisible }>
+			Toggle Popover!
+			<Popover
+				isOpen={ isVisible }
+				onClose={ toggleVisible }
+				onClick={ ( event ) => event.stopPropagation() }
+			>
+				Popover is toggled!
+			</Popover>
+		</button>
+	);
+}
+```
+
+## Props
+
+The component accepts the following props:
+
+### position
+
+The direction in which the popover should open relative to its parent node. Specify y- and x-axis as a space-separated string. Supports `"top"`, `"bottom"` y axis, and `"left"`, `"center"`, `"right"` x axis.
+
+- Type: `String`
+- Required: No
+- Default: `"top center"`
+
+### children
+
+The content to be displayed within the popover.
+
+- Type: `Element`
+- Required: Yes
+
+### className
+
+An optional additional class name to apply to the rendered popover.
+
+- Type: `String`
+- Required: No

components/popover/detect-outside.js

@@ -0,0 +1,24 @@
+/**
+ * External dependencies
+ */
+import clickOutside from 'react-click-outside';
+
+/**
+ * WordPress dependencies
+ */
+import { Component } from '@wordpress/element';
+
+class PopoverDetectOutside extends Component {
+	handleClickOutside( event ) {
+		const { onClickOutside } = this.props;
+		if ( onClickOutside ) {
+			onClickOutside( event );
+		}
+	}
+
+	render() {
+		return this.props.children;
+	}
+}
+
+export default clickOutside( PopoverDetectOutside );

components/popover/index.js

@@ -2,22 +2,35 @@
  * External dependencies
  */
 import classnames from 'classnames';
+import { isEqual, pickBy } from 'lodash';
 
 /**
  * WordPress dependencies
  */
-import { Component } from '@wordpress/element';
+import { createPortal, Component } from '@wordpress/element';
 
 /**
  * Internal dependencies
  */
 import './style.scss';
+import PopoverDetectOutside from './detect-outside';
 
-class Popover extends Component {
+/**
+ * Matches an event handler prop key
+ *
+ * @type {RegExp}
+ */
+const REGEXP_EVENT_PROP = /^on[A-Z]/;
+
+export class Popover extends Component {
 	constructor() {
 		super( ...arguments );
 
-		this.bindContent = this.bindContent.bind( this );
+		this.bindNode = this.bindNode.bind( this );
+		this.setOffset = this.setOffset.bind( this );
+		this.throttledSetOffset = this.throttledSetOffset.bind( this );
+
+		this.nodes = {};
 
 		this.state = {
 			forcedYAxis: null,
@@ -26,7 +39,11 @@ class Popover extends Component {
 	}
 
 	componentDidMount() {
-		this.setForcedPositions();
+		if ( this.props.isOpen ) {
+			this.setOffset();
+			this.setForcedPositions();
+			this.toggleWindowEvents( true );
+		}
 	}
 
 	componentWillReceiveProps( nextProps ) {
@@ -38,14 +55,61 @@ class Popover extends Component {
 		}
 	}
 
-	componentDidUpdate( prevProps ) {
-		if ( this.props.position !== prevProps.position ) {
+	componentDidUpdate( prevProps, prevState ) {
+		const { isOpen, position } = this.props;
+		const { isOpen: prevIsOpen, position: prevPosition } = prevProps;
+		if ( isOpen !== prevIsOpen ) {
+			this.toggleWindowEvents( isOpen );
+		}
+
+		if ( ! isOpen ) {
+			return;
+		}
+
+		if ( isOpen !== prevIsOpen || position !== prevPosition ) {
+			this.setOffset();
 			this.setForcedPositions();
+		} else if ( ! isEqual( this.state, prevState ) ) {
+			// Need to update offset if forced positioning applied
+			this.setOffset();
 		}
 	}
 
+	componentWillUnmount() {
+		this.toggleWindowEvents( false );
+	}
+
+	toggleWindowEvents( isListening ) {
+		const handler = isListening ? 'addEventListener' : 'removeEventListener';
+
+		window.cancelAnimationFrame( this.rafHandle );
+		window[ handler ]( 'resize', this.throttledSetOffset );
+		window[ handler ]( 'scroll', this.throttledSetOffset );
+	}
+
+	throttledSetOffset() {
+		this.rafHandle = window.requestAnimationFrame( this.setOffset );
+	}
+
+	setOffset() {
+		const { anchor, popover } = this.nodes;
+		const { parentNode } = anchor;
+		if ( ! parentNode ) {
+			return;
+		}
+
+		const rect = parentNode.getBoundingClientRect();
+
+		// Set popover at parent node center
+		popover.style.left = Math.round( rect.left + ( rect.width / 2 ) ) + 'px';
+
+		// Set at top or bottom of parent node based on popover position
+		const [ yAxis ] = this.getPositions();
+		popover.style.top = rect[ yAxis ] + 'px';
+	}
+
 	setForcedPositions() {
-		const rect = this.content.getBoundingClientRect();
+		const rect = this.nodes.content.getBoundingClientRect();
 
 		// Check exceeding top or bottom of viewport
 		if ( rect.top < 0 ) {
@@ -62,28 +126,61 @@ class Popover extends Component {
 		}
 	}
 
-	bindContent( node ) {
-		this.content = node;
+	getPositions() {
+		const { position = 'top' } = this.props;
+		const [ yAxis, xAxis = 'center' ] = position.split( ' ' );
+		const { forcedYAxis, forcedXAxis } = this.state;
+
+		return [
+			forcedYAxis || yAxis,
+			forcedXAxis || xAxis,
+		];
+	}
+
+	bindNode( name ) {
+		return ( node ) => this.nodes[ name ] = node;
 	}
 
 	render() {
-		const { position, children, className } = this.props;
-		const { forcedYAxis, forcedXAxis } = this.state;
-		const [ yAxis = 'top', xAxis = 'center' ] = position.split( ' ' );
+		const { isOpen, onClose, children, className } = this.props;
+		const [ yAxis, xAxis ] = this.getPositions();
+
+		if ( ! isOpen ) {
+			return null;
+		}
+
+		const eventHandlers = pickBy( this.props, ( value, key ) => (
+			'onClose' !== key && REGEXP_EVENT_PROP.test( key )
+		) );
 
 		const classes = classnames(
 			'components-popover',
 			className,
-			'is-' + ( forcedYAxis || yAxis ),
-			'is-' + ( forcedXAxis || xAxis )
+			'is-' + yAxis,
+			'is-' + xAxis,
 		);
 
 		return (
-			<div className={ classes } tabIndex="0">
-				<div ref={ this.bindContent } className="components-popover__content">
-					{ children }
-				</div>
-			</div>
+			<span ref={ this.bindNode( 'anchor' ) }>
+				{ createPortal(
+					<PopoverDetectOutside onClickOutside={ onClose }>
+						<div
+							ref={ this.bindNode( 'popover' ) }
+							className={ classes }
+							tabIndex="0"
+							{ ...eventHandlers }
+						>
+							<div
+								ref={ this.bindNode( 'content' ) }
+								className="components-popover__content"
+							>
+								{ children }
+							</div>
+						</div>
+					</PopoverDetectOutside>,
+					document.body
+				) }
+			</span>
 		);
 	}
 }

components/popover/style.scss

@@ -1,5 +1,9 @@
 .components-popover {
-	position: absolute;
+	&, * {
+		box-sizing: border-box;
+	}
+
+	position: fixed;
 	z-index: z-index( ".components-popover" );
 	left: 50%;
 
@@ -77,10 +81,6 @@
 		bottom: 100%;
 	}
 
-	.components-popover.is-bottom & {
-		top: 100%;
-	}
-
 	.components-popover.is-center & {
 		left: 50%;
 		transform: translateX( -50% );