Add customize widgets inserter

packages/customize-widgets/package.json

@@ -27,9 +27,11 @@
 		"@wordpress/components": "file:../components",
 		"@wordpress/compose": "file:../compose",
 		"@wordpress/data": "file:../data",
+		"@wordpress/dom": "file:../dom",
 		"@wordpress/element": "file:../element",
 		"@wordpress/i18n": "file:../i18n",
 		"@wordpress/icons": "file:../icons",
+		"@wordpress/keycodes": "file:../keycodes",
 		"classnames": "^2.2.6",
 		"lodash": "^4.17.19"
 	},

packages/customize-widgets/src/components/header/index.js

@@ -0,0 +1,48 @@
+/**
+ * WordPress dependencies
+ */
+import { createPortal } from '@wordpress/element';
+import { __, _x } from '@wordpress/i18n';
+import { Button, ToolbarItem } from '@wordpress/components';
+import { NavigableToolbar } from '@wordpress/block-editor';
+import { plus } from '@wordpress/icons';
+
+/**
+ * Internal dependencies
+ */
+import Inserter from '../inserter';
+
+function Header( { inserter, isInserterOpened, setIsInserterOpened } ) {
+	return (
+		<>
+			<div className="customize-widgets-header">
+				<NavigableToolbar
+					className="customize-widgets-header-toolbar"
+					aria-label={ __( 'Document tools' ) }
+				>
+					<ToolbarItem
+						as={ Button }
+						className="customize-widgets-header-toolbar__inserter-toggle"
+						isPressed={ isInserterOpened }
+						isPrimary
+						icon={ plus }
+						label={ _x(
+							'Add block',
+							'Generic label for block inserter button'
+						) }
+						onClick={ () => {
+							setIsInserterOpened( ( isOpen ) => ! isOpen );
+						} }
+					/>
+				</NavigableToolbar>
+			</div>
+
+			{ createPortal(
+				<Inserter setIsOpened={ setIsInserterOpened } />,
+				inserter.contentContainer[ 0 ]
+			) }
+		</>
+	);
+}
+
+export default Header;

packages/customize-widgets/src/components/header/style.scss

@@ -0,0 +1,21 @@
+.customize-widgets-header-toolbar {
+	display: flex;
+	border: none;
+
+	.customize-widgets-header-toolbar__inserter-toggle.components-button.has-icon {
+		border-radius: 2px;
+		color: $white;
+		padding: 0;
+		min-width: $grid-unit-30;
+		height: $grid-unit-30;
+		margin-left: auto;
+
+		&::before {
+			content: none;
+		}
+
+		&.is-pressed {
+			background: $gray-900;
+		}
+	}
+}

packages/customize-widgets/src/components/inserter/index.js

@@ -0,0 +1,45 @@
+/**
+ * WordPress dependencies
+ */
+import { __ } from '@wordpress/i18n';
+import { __experimentalLibrary as Library } from '@wordpress/block-editor';
+import { Button } from '@wordpress/components';
+import { useInstanceId } from '@wordpress/compose';
+import { closeSmall } from '@wordpress/icons';
+
+function Inserter( { setIsOpened } ) {
+	const inserterTitleId = useInstanceId(
+		Inserter,
+		'customize-widget-layout__inserter-panel-title'
+	);
+
+	return (
+		<div
+			className="customize-widgets-layout__inserter-panel"
+			aria-labelledby={ inserterTitleId }
+		>
+			<div className="customize-widgets-layout__inserter-panel-header">
+				<h2
+					id={ inserterTitleId }
+					className="customize-widgets-layout__inserter-panel-header-title"
+				>
+					{ __( 'Add a block' ) }
+				</h2>
+				<Button
+					className="customize-widgets-layout__inserter-panel-header-close-button"
+					icon={ closeSmall }
+					onClick={ () => setIsOpened( false ) }
+					aria-label={ __( 'Close inserter' ) }
+				/>
+			</div>
+			<div className="customize-widgets-layout__inserter-panel-content">
+				<Library
+					showInserterHelpPanel
+					onSelect={ () => setIsOpened( false ) }
+				/>
+			</div>
+		</div>
+	);
+}
+
+export default Inserter;

packages/customize-widgets/src/components/inserter/style.scss

@@ -0,0 +1,40 @@
+#customize-sidebar-outer-content {
+	// To override the default style of width: 100%,
+	// so that the inspector won't be cropped.
+	width: auto;
+	min-width: 100%;
+}
+
+#customize-outer-theme-controls #sub-accordion-section-widgets-inserter {
+	padding: 0;
+
+	.customize-section-description-container {
+		display: none;
+	}
+}
+
+.customize-widgets-layout__inserter-panel {
+	background: $white;
+}
+
+.customize-widgets-layout__inserter-panel-header {
+	display: flex;
+	justify-content: space-between;
+	align-items: center;
+	padding: $grid-unit-20;
+	// Match the "wp-full-overlay-header" height in core, plus the 1px border.
+	height: 46px;
+	box-sizing: border-box;
+	border-bottom: 1px solid $gray-300;
+
+	.customize-widgets-layout__inserter-panel-header-title {
+		margin: 0;
+	}
+}
+
+.block-editor-inserter__quick-inserter {
+	.block-editor-inserter__panel-content {
+		// To fix quick inserter doesn't have background.
+		background: $white;
+	}
+}

packages/customize-widgets/src/components/inserter/use-inserter.js

@@ -0,0 +1,33 @@
+/**
+ * WordPress dependencies
+ */
+import { useState, useEffect, useCallback } from '@wordpress/element';
+
+export default function useInserter( inserter ) {
+	const [ isInserterOpened, setIsInserterOpened ] = useState(
+		() => inserter.isOpen
+	);
+
+	useEffect( () => {
+		return inserter.subscribe( setIsInserterOpened );
+	}, [ inserter ] );
+
+	return [
+		isInserterOpened,
+		useCallback(
+			( updater ) => {
+				let isOpen = updater;
+				if ( typeof updater === 'function' ) {
+					isOpen = updater( inserter.isOpen );
+				}
+
+				if ( isOpen ) {
+					inserter.open();
+				} else {
+					inserter.close();
+				}
+			},
+			[ inserter ]
+		),
+	];
+}

packages/customize-widgets/src/components/sidebar-block-editor/index.js

@@ -1,7 +1,7 @@
 /**
  * WordPress dependencies
  */
-import { useReducer, createPortal } from '@wordpress/element';
+import { useReducer, createPortal, useMemo } from '@wordpress/element';
 import {
 	BlockEditorProvider,
 	BlockList,
@@ -21,7 +21,9 @@ import {
  * Internal dependencies
  */
 import Inspector, { BlockInspectorButton } from '../inspector';
+import Header from '../header';
 import useSidebarBlockEditor from './use-sidebar-block-editor';
+import useInserter from '../inserter/use-inserter';
 
 const inspectorOpenStateReducer = ( state, action ) => {
 	switch ( action ) {
@@ -45,7 +47,7 @@ const inspectorOpenStateReducer = ( state, action ) => {
 	}
 };
 
-export default function SidebarBlockEditor( { sidebar } ) {
+export default function SidebarBlockEditor( { sidebar, inserter } ) {
 	const [ blocks, onInput, onChange ] = useSidebarBlockEditor( sidebar );
 	const [
 		{ open: isInspectorOpened, busy: isInspectorAnimating },
@@ -54,6 +56,13 @@ export default function SidebarBlockEditor( { sidebar } ) {
 	const parentContainer = document.getElementById(
 		'customize-theme-controls'
 	);
+	const [ isInserterOpened, setIsInserterOpened ] = useInserter( inserter );
+	const settings = useMemo(
+		() => ( {
+			__experimentalSetIsInserterOpened: setIsInserterOpened,
+		} ),
+		[]
+	);
 
 	return (
 		<>
@@ -65,10 +74,17 @@ export default function SidebarBlockEditor( { sidebar } ) {
 							value={ blocks }
 							onInput={ onInput }
 							onChange={ onChange }
+							settings={ settings }
 							useSubRegistry={ false }
 						>
 							<BlockEditorKeyboardShortcuts />
 
+							<Header
+								inserter={ inserter }
+								isInserterOpened={ isInserterOpened }
+								setIsInserterOpened={ setIsInserterOpened }
+							/>
+
 							<BlockSelectionClearer>
 								<WritingFlow>
 									<ObserveTyping>

packages/customize-widgets/src/controls/inserter-outer-section.js

@@ -0,0 +1,118 @@
+/**
+ * WordPress dependencies
+ */
+import { ESCAPE } from '@wordpress/keycodes';
+import { focus } from '@wordpress/dom';
+
+const {
+	wp: { customize },
+} = window;
+
+const OuterSection = customize.OuterSection;
+// Override the OuterSection class to handle multiple outer sections.
+// It closes all the other outer sections whenever one is opened.
+// The result is that at most one outer section can be opened at the same time.
+customize.OuterSection = class extends OuterSection {
+	onChangeExpanded( expanded, args ) {
+		if ( expanded ) {
+			customize.section.each( ( section ) => {
+				if (
+					section.params.type === 'outer' &&
+					section.id !== this.id
+				) {
+					if ( section.expanded() ) {
+						section.collapse();
+					}
+				}
+			} );
+		}
+
+		return super.onChangeExpanded( expanded, args );
+	}
+};
+// Handle constructor so that "params.type" can be correctly pointed to "outer".
+customize.sectionConstructor.outer = customize.OuterSection;
+
+class InserterOuterSection extends customize.OuterSection {
+	constructor( ...args ) {
+		super( ...args );
+
+		// This is necessary since we're creating a new class which is not identical to the original OuterSection.
+		// @See https://github.com/WordPress/wordpress-develop/blob/42b05c397c50d9dc244083eff52991413909d4bd/src/js/_enqueues/wp/customize/controls.js#L1427-L1436
+		this.params.type = 'outer';
+
+		this.activeElementBeforeExpanded = null;
+
+		const ownerWindow = this.contentContainer[ 0 ].ownerDocument
+			.defaultView;
+
+		// Handle closing the inserter when pressing the Escape key.
+		ownerWindow.addEventListener(
+			'keydown',
+			( event ) => {
+				if (
+					this.isOpen &&
+					( event.keyCode === ESCAPE || event.code === 'Escape' )
+				) {
+					event.stopPropagation();
+
+					this.close();
+				}
+			},
+			// Use capture mode to make this run before other event listeners.
+			true
+		);
+	}
+	get isOpen() {
+		return this.expanded();
+	}
+	subscribe( handler ) {
+		this.expanded.bind( handler );
+		return () => this.expanded.unbind( handler );
+	}
+	open() {
+		if ( ! this.isOpen ) {
+			const contentContainer = this.contentContainer[ 0 ];
+			this.activeElementBeforeExpanded =
+				contentContainer.ownerDocument.activeElement;
+
+			this.expand( {
+				completeCallback() {
+					// We have to do this in a "completeCallback" or else the elements will not yet be visible/tabbable.
+					// The first one should be the close button,
+					// we want to skip it and choose the second one instead, which is the search box.
+					const searchBox = focus.tabbable.find(
+						contentContainer
+					)[ 1 ];
+					if ( searchBox ) {
+						searchBox.focus();
+					}
+				},
+			} );
+		}
+	}
+	close() {
+		if ( this.isOpen ) {
+			const contentContainer = this.contentContainer[ 0 ];
+			const activeElement = contentContainer.ownerDocument.activeElement;
+
+			this.collapse( {
+				completeCallback() {
+					// Return back the focus when closing the inserter.
+					// Only do this if the active element which triggers the action is inside the inserter,
+					// (the close button for instance). In that case the focus will be lost.
+					// Otherwise, we don't hijack the focus when the user is focusing on other elements
+					// (like the quick inserter).
+					if ( contentContainer.contains( activeElement ) ) {
+						// Return back the focus when closing the inserter.
+						if ( this.activeElementBeforeExpanded ) {
+							this.activeElementBeforeExpanded.focus();
+						}
+					}
+				},
+			} );
+		}
+	}
+}
+
+export default InserterOuterSection;