From 666912edf9c341fc6504e59670a582bfedaa0eef Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@git.wordpress.org>
Date: Mon, 25 Sep 2017 06:27:32 +0000
Subject: [PATCH] Widgets: Introduce Gallery widget for displaying image
 galleries.

* Galleries are managed in the widget in the same way they are managed in the post editor, both using the media manager.
* Gallery widget is merged from the Core Media Widgets v0.2.0 feature plugin and it extends `WP_Widget_Media` in the same way as is done for image, audio, and video widgets.
* Model syncing logic is updated to support booleans and arrays (of integers).
* Placeholder areas in media widgets are now clickable shortcuts for selecting media.
* Image widget placeholder is updated to match gallery widget where clicking preview is shortcut for editing media.

Props westonruter, joemcgill, timmydcrawford, m1tk00, obenland, melchoyce.
See #32417.
Fixes #41914.


git-svn-id: https://develop.svn.wordpress.org/trunk@41590 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-admin/css/widgets.css                  |  67 +++-
 .../js/widgets/media-gallery-widget.js        | 325 ++++++++++++++++++
 src/wp-admin/js/widgets/media-image-widget.js |  10 +
 src/wp-admin/js/widgets/media-widgets.js      |  40 ++-
 src/wp-includes/default-widgets.php           |   3 +
 src/wp-includes/script-loader.php             |   1 +
 src/wp-includes/widgets.php                   |   2 +
 .../widgets/class-wp-widget-media-gallery.php | 224 ++++++++++++
 .../widgets/class-wp-widget-media.php         |  10 +-
 .../tests/widgets/media-gallery-widget.php    | 201 +++++++++++
 tests/qunit/index.html                        |  64 +++-
 .../js/widgets/test-media-gallery-widget.js   |  30 ++
 12 files changed, 965 insertions(+), 12 deletions(-)
 create mode 100644 src/wp-admin/js/widgets/media-gallery-widget.js
 create mode 100644 src/wp-includes/widgets/class-wp-widget-media-gallery.php
 create mode 100644 tests/phpunit/tests/widgets/media-gallery-widget.php
 create mode 100644 tests/qunit/wp-admin/js/widgets/test-media-gallery-widget.js

diff --git a/src/wp-admin/css/widgets.css b/src/wp-admin/css/widgets.css
index f31b63c881..e291590e70 100644
--- a/src/wp-admin/css/widgets.css
+++ b/src/wp-admin/css/widgets.css
@@ -87,7 +87,7 @@
 .media-widget-control .placeholder {
 	border: 1px dashed #b4b9be;
 	box-sizing: border-box;
-	cursor: default;
+	cursor: pointer;
 	line-height: 20px;
 	padding: 9px 0;
 	position: relative;
@@ -162,6 +162,71 @@
 	margin: 1em 0;
 }
 
+.media-widget-gallery-preview {
+	display: -webkit-box;
+	display: flex;
+	-webkit-box-pack: start;
+	justify-content: flex-start;
+	flex-wrap: wrap;
+}
+
+.media-widget-preview.media_gallery,
+.media-widget-preview.media_image {
+	cursor: pointer;
+}
+
+.media-widget-gallery-preview .gallery-item {
+	box-sizing: border-box;
+	width: 50%;
+	margin: 0;
+	padding: 1.79104477%;
+}
+
+/*
+ * Use targeted nth-last-child selectors to control the size of each image
+ * based on how many gallery items are present in the grid.
+ * See: https://alistapart.com/article/quantity-queries-for-css
+ */
+.media-widget-gallery-preview .gallery-item:nth-last-child(3):first-child,
+.media-widget-gallery-preview .gallery-item:nth-last-child(3):first-child ~ .gallery-item,
+.media-widget-gallery-preview .gallery-item:nth-last-child(n+5),
+.media-widget-gallery-preview .gallery-item:nth-last-child(n+5) ~ .gallery-item,
+.media-widget-gallery-preview .gallery-item:nth-last-child(n+6),
+.media-widget-gallery-preview .gallery-item:nth-last-child(n+6) ~ .gallery-item {
+	max-width: 33.33%;
+}
+
+.media-widget-gallery-preview .gallery-item img {
+	height: auto;
+	vertical-align: bottom;
+}
+
+.media-widget-gallery-preview .gallery-icon {
+	position: relative;
+}
+
+.media-widget-gallery-preview .gallery-icon-placeholder {
+	position: absolute;
+	top: 0;
+	bottom: 0;
+	width: 100%;
+	box-sizing: border-box;
+	display: -webkit-box;
+	display: flex;
+	-webkit-box-align: center;
+	align-items: center;
+	-webkit-box-pack: center;
+	justify-content: center;
+	background-color: rgba( 0, 0, 0, .5 );
+}
+
+.media-widget-gallery-preview .gallery-icon-placeholder-text {
+	font-weight: 600;
+	font-size: 2em;
+	color: white;
+}
+
+
 /* Widget Dragging Helpers */
 .widget.ui-draggable-dragging {
 	min-width: 100%;
diff --git a/src/wp-admin/js/widgets/media-gallery-widget.js b/src/wp-admin/js/widgets/media-gallery-widget.js
new file mode 100644
index 0000000000..f569968e89
--- /dev/null
+++ b/src/wp-admin/js/widgets/media-gallery-widget.js
@@ -0,0 +1,325 @@
+/* eslint consistent-this: [ "error", "control" ] */
+(function( component ) {
+	'use strict';
+
+	var GalleryWidgetModel, GalleryWidgetControl, GalleryDetailsMediaFrame;
+
+	/**
+	 * Custom gallery details frame.
+	 *
+	 * @since 4.9.0
+	 * @class GalleryDetailsMediaFrame
+	 * @constructor
+	 */
+	GalleryDetailsMediaFrame = wp.media.view.MediaFrame.Post.extend( {
+
+		/**
+		 * Create the default states.
+		 *
+		 * @since 4.9.0
+		 * @returns {void}
+		 */
+		createStates: function createStates() {
+			this.states.add([
+				new wp.media.controller.Library({
+					id:         'gallery',
+					title:      wp.media.view.l10n.createGalleryTitle,
+					priority:   40,
+					toolbar:    'main-gallery',
+					filterable: 'uploaded',
+					multiple:   'add',
+					editable:   true,
+
+					library:  wp.media.query( _.defaults({
+						type: 'image'
+					}, this.options.library ) )
+				}),
+
+				// Gallery states.
+				new wp.media.controller.GalleryEdit({
+					library: this.options.selection,
+					editing: this.options.editing,
+					menu:    'gallery'
+				}),
+
+				new wp.media.controller.GalleryAdd()
+			]);
+		}
+	} );
+
+	/**
+	 * Gallery widget model.
+	 *
+	 * See WP_Widget_Gallery::enqueue_admin_scripts() for amending prototype from PHP exports.
+	 *
+	 * @since 4.9.0
+	 * @class GalleryWidgetModel
+	 * @constructor
+	 */
+	GalleryWidgetModel = component.MediaWidgetModel.extend( {} );
+
+	/**
+	 * Gallery widget control.
+	 *
+	 * See WP_Widget_Gallery::enqueue_admin_scripts() for amending prototype from PHP exports.
+	 *
+	 * @since 4.9.0
+	 * @class GalleryWidgetControl
+	 * @constructor
+	 */
+	GalleryWidgetControl = component.MediaWidgetControl.extend( {
+
+		/**
+		 * View events.
+		 *
+		 * @since 4.9.0
+		 * @type {object}
+		 */
+		events: _.extend( {}, component.MediaWidgetControl.prototype.events, {
+			'click .media-widget-gallery-preview': 'editMedia'
+		} ),
+
+		/**
+		 * Initialize.
+		 *
+		 * @since 4.9.0
+		 * @param {Object}         options - Options.
+		 * @param {Backbone.Model} options.model - Model.
+		 * @param {jQuery}         options.el - Control field container element.
+		 * @param {jQuery}         options.syncContainer - Container element where fields are synced for the server.
+		 * @returns {void}
+		 */
+		initialize: function initialize( options ) {
+			var control = this;
+
+			component.MediaWidgetControl.prototype.initialize.call( control, options );
+
+			_.bindAll( control, 'updateSelectedAttachments', 'handleAttachmentDestroy' );
+			control.selectedAttachments = new wp.media.model.Attachments();
+			control.model.on( 'change:ids', control.updateSelectedAttachments );
+			control.selectedAttachments.on( 'change', control.renderPreview );
+			control.selectedAttachments.on( 'reset', control.renderPreview );
+			control.updateSelectedAttachments();
+		},
+
+		/**
+		 * Update the selected attachments if necessary.
+		 *
+		 * @since 4.9.0
+		 * @returns {void}
+		 */
+		updateSelectedAttachments: function updateSelectedAttachments() {
+			var control = this, newIds, oldIds, removedIds, addedIds, addedQuery;
+
+			newIds = control.model.get( 'ids' );
+			oldIds = _.pluck( control.selectedAttachments.models, 'id' );
+
+			removedIds = _.difference( oldIds, newIds );
+			_.each( removedIds, function( removedId ) {
+				control.selectedAttachments.remove( control.selectedAttachments.get( removedId ) );
+			});
+
+			addedIds = _.difference( newIds, oldIds );
+			if ( addedIds.length ) {
+				addedQuery = wp.media.query({
+					order: 'ASC',
+					orderby: 'post__in',
+					perPage: -1,
+					post__in: newIds,
+					query: true,
+					type: 'image'
+				});
+				addedQuery.more().done( function() {
+					control.selectedAttachments.reset( addedQuery.models );
+				});
+			}
+		},
+
+		/**
+		 * Render preview.
+		 *
+		 * @since 4.9.0
+		 * @returns {void}
+		 */
+		renderPreview: function renderPreview() {
+			var control = this, previewContainer, previewTemplate, data;
+
+			previewContainer = control.$el.find( '.media-widget-preview' );
+			previewTemplate = wp.template( 'wp-media-widget-gallery-preview' );
+
+			data = control.previewTemplateProps.toJSON();
+			data.attachments = {};
+			control.selectedAttachments.each( function( attachment ) {
+				data.attachments[ attachment.id ] = attachment.toJSON();
+			} );
+
+			previewContainer.html( previewTemplate( data ) );
+		},
+
+		/**
+		 * Determine whether there are selected attachments.
+		 *
+		 * @since 4.9.0
+		 * @returns {boolean} Selected.
+		 */
+		isSelected: function isSelected() {
+			var control = this;
+
+			if ( control.model.get( 'error' ) ) {
+				return false;
+			}
+
+			return control.model.get( 'ids' ).length > 0;
+		},
+
+		/**
+		 * Open the media select frame to edit images.
+		 *
+		 * @since 4.9.0
+		 * @returns {void}
+		 */
+		editMedia: function editMedia() {
+			var control = this, selection, mediaFrame, mediaFrameProps;
+
+			selection = new wp.media.model.Selection( control.selectedAttachments.models, {
+				multiple: true
+			});
+
+			mediaFrameProps = control.mapModelToMediaFrameProps( control.model.toJSON() );
+			selection.gallery = new Backbone.Model( _.pick( mediaFrameProps, 'columns', 'link', 'size', '_orderbyRandom' ) );
+			if ( mediaFrameProps.size ) {
+				control.displaySettings.set( 'size', mediaFrameProps.size );
+			}
+			mediaFrame = new GalleryDetailsMediaFrame({
+				frame: 'manage',
+				text: control.l10n.add_to_widget,
+				selection: selection,
+				mimeType: control.mime_type,
+				selectedDisplaySettings: control.displaySettings,
+				showDisplaySettings: control.showDisplaySettings,
+				metadata: mediaFrameProps,
+				editing:   true,
+				multiple:  true,
+				state: 'gallery-edit'
+			});
+			wp.media.frame = mediaFrame; // See wp.media().
+
+			// Handle selection of a media item.
+			mediaFrame.on( 'update', function onUpdate( newSelection ) {
+				var state = mediaFrame.state(), resultSelection;
+
+				resultSelection = newSelection || state.get( 'selection' );
+				if ( ! resultSelection ) {
+					return;
+				}
+
+				// Copy orderby_random from gallery state.
+				if ( resultSelection.gallery ) {
+					control.model.set( control.mapMediaToModelProps( resultSelection.gallery.toJSON() ) );
+				}
+
+				// Directly update selectedAttachments to prevent needing to do additional request.
+				control.selectedAttachments.reset( resultSelection.models );
+
+				// Update models in the widget instance.
+				control.model.set( {
+					ids: _.pluck( resultSelection.models, 'id' )
+				} );
+			} );
+
+			mediaFrame.$el.addClass( 'media-widget' );
+			mediaFrame.open();
+
+			if ( selection ) {
+				selection.on( 'destroy', control.handleAttachmentDestroy );
+			}
+		},
+
+		/**
+		 * Open the media select frame to chose an item.
+		 *
+		 * @since 4.9.0
+		 * @returns {void}
+		 */
+		selectMedia: function selectMedia() {
+			var control = this, selection, mediaFrame, mediaFrameProps;
+			selection = new wp.media.model.Selection( control.selectedAttachments.models, {
+				multiple: true
+			});
+
+			mediaFrameProps = control.mapModelToMediaFrameProps( control.model.toJSON() );
+			if ( mediaFrameProps.size ) {
+				control.displaySettings.set( 'size', mediaFrameProps.size );
+			}
+			mediaFrame = new GalleryDetailsMediaFrame({
+				frame: 'select',
+				text: control.l10n.add_to_widget,
+				selection: selection,
+				mimeType: control.mime_type,
+				selectedDisplaySettings: control.displaySettings,
+				showDisplaySettings: control.showDisplaySettings,
+				metadata: mediaFrameProps,
+				state: 'gallery'
+			});
+			wp.media.frame = mediaFrame; // See wp.media().
+
+			// Handle selection of a media item.
+			mediaFrame.on( 'update', function onUpdate( newSelection ) {
+				var state = mediaFrame.state(), resultSelection;
+
+				resultSelection = newSelection || state.get( 'selection' );
+				if ( ! resultSelection ) {
+					return;
+				}
+
+				// Copy orderby_random from gallery state.
+				if ( resultSelection.gallery ) {
+					control.model.set( control.mapMediaToModelProps( resultSelection.gallery.toJSON() ) );
+				}
+
+				// Directly update selectedAttachments to prevent needing to do additional request.
+				control.selectedAttachments.reset( resultSelection.models );
+
+				// Update widget instance.
+				control.model.set( {
+					ids: _.pluck( resultSelection.models, 'id' )
+				} );
+			} );
+
+			mediaFrame.$el.addClass( 'media-widget' );
+			mediaFrame.open();
+
+			if ( selection ) {
+				selection.on( 'destroy', control.handleAttachmentDestroy );
+			}
+
+			/*
+			 * Make sure focus is set inside of modal so that hitting Esc will close
+			 * the modal and not inadvertently cause the widget to collapse in the customizer.
+			 */
+			mediaFrame.$el.find( ':focusable:first' ).focus();
+		},
+
+		/**
+		 * Clear the selected attachment when it is deleted in the media select frame.
+		 *
+		 * @since 4.9.0
+		 * @param {wp.media.models.Attachment} attachment - Attachment.
+		 * @returns {void}
+		 */
+		handleAttachmentDestroy: function handleAttachmentDestroy( attachment ) {
+			var control = this;
+			control.model.set( {
+				ids: _.difference(
+					control.model.get( 'ids' ),
+					[ attachment.id ]
+				)
+			} );
+		}
+	} );
+
+	// Exports.
+	component.controlConstructors.media_gallery = GalleryWidgetControl;
+	component.modelConstructors.media_gallery = GalleryWidgetModel;
+
+})( wp.mediaWidgets );
diff --git a/src/wp-admin/js/widgets/media-image-widget.js b/src/wp-admin/js/widgets/media-image-widget.js
index ddbe6b3e24..78b257feae 100644
--- a/src/wp-admin/js/widgets/media-image-widget.js
+++ b/src/wp-admin/js/widgets/media-image-widget.js
@@ -24,6 +24,15 @@
 	 */
 	ImageWidgetControl = component.MediaWidgetControl.extend({
 
+		/**
+		 * View events.
+		 *
+		 * @type {object}
+		 */
+		events: _.extend( {}, component.MediaWidgetControl.prototype.events, {
+			'click .media-widget-preview.populated': 'editMedia'
+		} ),
+
 		/**
 		 * Render preview.
 		 *
@@ -38,6 +47,7 @@
 			previewContainer = control.$el.find( '.media-widget-preview' );
 			previewTemplate = wp.template( 'wp-media-widget-image-preview' );
 			previewContainer.html( previewTemplate( control.previewTemplateProps.toJSON() ) );
+			previewContainer.addClass( 'populated' );
 
 			linkInput = control.$el.find( '.link' );
 			if ( ! linkInput.is( document.activeElement ) ) {
diff --git a/src/wp-admin/js/widgets/media-widgets.js b/src/wp-admin/js/widgets/media-widgets.js
index e3bc41c480..5e7383c6fc 100644
--- a/src/wp-admin/js/widgets/media-widgets.js
+++ b/src/wp-admin/js/widgets/media-widgets.js
@@ -429,6 +429,7 @@ wp.mediaWidgets = ( function( $ ) {
 		events: {
 			'click .notice-missing-attachment a': 'handleMediaLibraryLinkClick',
 			'click .select-media': 'selectMedia',
+			'click .placeholder': 'selectMedia',
 			'click .edit-media': 'editMedia'
 		},
 
@@ -591,17 +592,25 @@ wp.mediaWidgets = ( function( $ ) {
 		syncModelToInputs: function syncModelToInputs() {
 			var control = this;
 			control.syncContainer.find( '.media-widget-instance-property' ).each( function() {
-				var input = $( this ), value;
-				value = control.model.get( input.data( 'property' ) );
+				var input = $( this ), value, propertyName;
+				propertyName = input.data( 'property' );
+				value = control.model.get( propertyName );
 				if ( _.isUndefined( value ) ) {
 					return;
 				}
-				value = String( value );
-				if ( input.val() === value ) {
-					return;
+
+				if ( 'array' === control.model.schema[ propertyName ].type && _.isArray( value ) ) {
+					value = value.join( ',' );
+				} else if ( 'boolean' === control.model.schema[ propertyName ].type ) {
+					value = value ? '1' : ''; // Because in PHP, strval( true ) === '1' && strval( false ) === ''.
+				} else {
+					value = String( value );
+				}
+
+				if ( input.val() !== value ) {
+					input.val( value );
+					input.trigger( 'change' );
 				}
-				input.val( value );
-				input.trigger( 'change' );
 			});
 		},
 
@@ -1002,7 +1011,22 @@ wp.mediaWidgets = ( function( $ ) {
 					return;
 				}
 				type = model.schema[ name ].type;
-				if ( 'integer' === type ) {
+				if ( 'array' === type ) {
+					castedAttrs[ name ] = value;
+					if ( ! _.isArray( castedAttrs[ name ] ) ) {
+						castedAttrs[ name ] = castedAttrs[ name ].split( /,/ ); // Good enough for parsing an ID list.
+					}
+					if ( model.schema[ name ].items && 'integer' === model.schema[ name ].items.type ) {
+						castedAttrs[ name ] = _.filter(
+							_.map( castedAttrs[ name ], function( id ) {
+								return parseInt( id, 10 );
+							},
+							function( id ) {
+								return 'number' === typeof id;
+							}
+						) );
+					}
+				} else if ( 'integer' === type ) {
 					castedAttrs[ name ] = parseInt( value, 10 );
 				} else if ( 'boolean' === type ) {
 					castedAttrs[ name ] = ! ( ! value || '0' === value || 'false' === value );
diff --git a/src/wp-includes/default-widgets.php b/src/wp-includes/default-widgets.php
index 7c8a903c56..767002b642 100644
--- a/src/wp-includes/default-widgets.php
+++ b/src/wp-includes/default-widgets.php
@@ -31,6 +31,9 @@ require_once( ABSPATH . WPINC . '/widgets/class-wp-widget-media-image.php' );
 /** WP_Widget_Media_Video class */
 require_once( ABSPATH . WPINC . '/widgets/class-wp-widget-media-video.php' );
 
+/** WP_Widget_Media_Gallery class */
+require_once( ABSPATH . WPINC . '/widgets/class-wp-widget-media-gallery.php' );
+
 /** WP_Widget_Meta class */
 require_once( ABSPATH . WPINC . '/widgets/class-wp-widget-meta.php' );
 
diff --git a/src/wp-includes/script-loader.php b/src/wp-includes/script-loader.php
index c85822c807..fa1ada70fb 100644
--- a/src/wp-includes/script-loader.php
+++ b/src/wp-includes/script-loader.php
@@ -699,6 +699,7 @@ function wp_default_scripts( &$scripts ) {
 
 		$scripts->add( 'media-audio-widget', "/wp-admin/js/widgets/media-audio-widget$suffix.js", array( 'media-widgets', 'media-audiovideo' ) );
 		$scripts->add( 'media-image-widget', "/wp-admin/js/widgets/media-image-widget$suffix.js", array( 'media-widgets' ) );
+		$scripts->add( 'media-gallery-widget', "/wp-admin/js/widgets/media-gallery-widget$suffix.js", array( 'media-widgets' ) );
 		$scripts->add( 'media-video-widget', "/wp-admin/js/widgets/media-video-widget$suffix.js", array( 'media-widgets', 'media-audiovideo', 'wp-api-request' ) );
 		$scripts->add( 'text-widgets', "/wp-admin/js/widgets/text-widgets$suffix.js", array( 'jquery', 'backbone', 'editor', 'wp-util', 'wp-a11y' ) );
 		$scripts->add( 'custom-html-widgets', "/wp-admin/js/widgets/custom-html-widgets$suffix.js", array( 'code-editor', 'jquery', 'backbone', 'wp-util', 'jquery-ui-core', 'wp-a11y' ) );
diff --git a/src/wp-includes/widgets.php b/src/wp-includes/widgets.php
index fe0e058d9a..e4fcc527b7 100644
--- a/src/wp-includes/widgets.php
+++ b/src/wp-includes/widgets.php
@@ -1609,6 +1609,8 @@ function wp_widgets_init() {
 
 	register_widget( 'WP_Widget_Media_Image' );
 
+	register_widget( 'WP_Widget_Media_Gallery' );
+
 	register_widget( 'WP_Widget_Media_Video' );
 
 	register_widget( 'WP_Widget_Meta' );
diff --git a/src/wp-includes/widgets/class-wp-widget-media-gallery.php b/src/wp-includes/widgets/class-wp-widget-media-gallery.php
new file mode 100644
index 0000000000..5c07c4fc6b
--- /dev/null
+++ b/src/wp-includes/widgets/class-wp-widget-media-gallery.php
@@ -0,0 +1,224 @@
+<?php
+/**
+ * Widget API: WP_Widget_Media_Gallery class
+ *
+ * @package WordPress
+ * @subpackage Widgets
+ * @since 4.9.0
+ */
+
+/**
+ * Core class that implements a gallery widget.
+ *
+ * @since 4.9.0
+ *
+ * @see WP_Widget
+ */
+class WP_Widget_Media_Gallery extends WP_Widget_Media {
+
+	/**
+	 * Constructor.
+	 *
+	 * @since 4.9.0
+	 */
+	public function __construct() {
+		parent::__construct( 'media_gallery', __( 'Gallery' ), array(
+			'description' => __( 'Displays an image gallery.' ),
+			'mime_type'   => 'image',
+		) );
+
+		$this->l10n = array_merge( $this->l10n, array(
+			'no_media_selected' => __( 'No images selected' ),
+			'add_media' => _x( 'Select Images', 'label for button in the gallery widget; should not be longer than ~13 characters long' ),
+			'replace_media' => _x( 'Replace Gallery', 'label for button in the gallery widget; should not be longer than ~13 characters long' ),
+			'edit_media' => _x( 'Edit Gallery', 'label for button in the gallery widget; should not be longer than ~13 characters long' ),
+		) );
+	}
+
+	/**
+	 * Get schema for properties of a widget instance (item).
+	 *
+	 * @since 4.9.0
+	 *
+	 * @see WP_REST_Controller::get_item_schema()
+	 * @see WP_REST_Controller::get_additional_fields()
+	 * @link https://core.trac.wordpress.org/ticket/35574
+	 * @return array Schema for properties.
+	 */
+	public function get_instance_schema() {
+		return array(
+			'title' => array(
+				'type' => 'string',
+				'default' => '',
+				'sanitize_callback' => 'sanitize_text_field',
+				'description' => __( 'Title for the widget' ),
+				'should_preview_update' => false,
+			),
+			'ids' => array(
+				'type' => 'array',
+				'items' => array(
+					'type' => 'integer',
+				),
+				'default' => array(),
+				'sanitize_callback' => 'wp_parse_id_list',
+			),
+			'columns' => array(
+				'type' => 'integer',
+				'default' => 3,
+				'minimum' => 1,
+				'maximum' => 9,
+			),
+			'size' => array(
+				'type' => 'string',
+				'enum' => array_merge( get_intermediate_image_sizes(), array( 'full', 'custom' ) ),
+				'default' => 'thumbnail',
+			),
+			'link_type' => array(
+				'type' => 'string',
+				'enum' => array( 'none', 'file', 'post' ),
+				'default' => 'none',
+				'media_prop' => 'link',
+				'should_preview_update' => false,
+			),
+			'orderby_random' => array(
+				'type'                  => 'boolean',
+				'default'               => false,
+				'media_prop'            => '_orderbyRandom',
+				'should_preview_update' => false,
+			),
+		);
+	}
+
+	/**
+	 * Render the media on the frontend.
+	 *
+	 * @since 4.9.0
+	 *
+	 * @param array $instance Widget instance props.
+	 * @return void
+	 */
+	public function render_media( $instance ) {
+		$instance = array_merge( wp_list_pluck( $this->get_instance_schema(), 'default' ), $instance );
+
+		$shortcode_atts = array(
+			'ids'     => $instance['ids'],
+			'columns' => $instance['columns'],
+			'link'    => $instance['link_type'],
+			'size'    => $instance['size'],
+		);
+
+		// @codeCoverageIgnoreStart
+		if ( $instance['orderby_random'] ) {
+			$shortcode_atts['orderby'] = 'rand';
+		}
+
+		// @codeCoverageIgnoreEnd
+		echo gallery_shortcode( $shortcode_atts );
+	}
+
+	/**
+	 * Loads the required media files for the media manager and scripts for media widgets.
+	 *
+	 * @since 4.9.0
+	 */
+	public function enqueue_admin_scripts() {
+		parent::enqueue_admin_scripts();
+
+		$handle = 'media-gallery-widget';
+		wp_enqueue_script( $handle );
+
+		$exported_schema = array();
+		foreach ( $this->get_instance_schema() as $field => $field_schema ) {
+			$exported_schema[ $field ] = wp_array_slice_assoc( $field_schema, array( 'type', 'default', 'enum', 'minimum', 'format', 'media_prop', 'should_preview_update', 'items' ) );
+		}
+		wp_add_inline_script(
+			$handle,
+			sprintf(
+				'wp.mediaWidgets.modelConstructors[ %s ].prototype.schema = %s;',
+				wp_json_encode( $this->id_base ),
+				wp_json_encode( $exported_schema )
+			)
+		);
+
+		wp_add_inline_script(
+			$handle,
+			sprintf(
+				'
+					wp.mediaWidgets.controlConstructors[ %1$s ].prototype.mime_type = %2$s;
+					_.extend( wp.mediaWidgets.controlConstructors[ %1$s ].prototype.l10n, %3$s );
+				',
+				wp_json_encode( $this->id_base ),
+				wp_json_encode( $this->widget_options['mime_type'] ),
+				wp_json_encode( $this->l10n )
+			)
+		);
+	}
+
+	/**
+	 * Render form template scripts.
+	 *
+	 * @since 4.9.0
+	 */
+	public function render_control_template_scripts() {
+		parent::render_control_template_scripts();
+		?>
+		<script type="text/html" id="tmpl-wp-media-widget-gallery-preview">
+			<# var describedById = 'describedBy-' + String( Math.random() ); #>
+			<# if ( data.ids.length ) { #>
+				<div class="gallery media-widget-gallery-preview">
+					<# _.each( data.ids, function( id, index ) { #>
+						<#
+						var attachment = data.attachments[ id ];
+						if ( ! attachment ) {
+							return;
+						}
+						#>
+						<# if ( index < 6 ) { #>
+							<dl class="gallery-item">
+								<dt class="gallery-icon">
+								<# if ( attachment.sizes.thumbnail ) { #>
+									<img src="{{ attachment.sizes.thumbnail.url }}" width="{{ attachment.sizes.thumbnail.width }}" height="{{ attachment.sizes.thumbnail.height }}" alt="" />
+								<# } else { #>
+									<img src="{{ attachment.url }}" alt="" />
+								<# } #>
+								<# if ( index === 5 && data.ids.length > 6 ) { #>
+									<div class="gallery-icon-placeholder">
+										<p class="gallery-icon-placeholder-text">+{{ data.ids.length - 5 }}</p>
+									</div>
+								<# } #>
+								</dt>
+							</dl>
+						<# } #>
+					<# } ); #>
+				</div>
+			<# } else { #>
+				<div class="attachment-media-view">
+					<p class="placeholder"><?php echo esc_html( $this->l10n['no_media_selected'] ); ?></p>
+				</div>
+			<# } #>
+		</script>
+		<?php
+	}
+
+	/**
+	 * Whether the widget has content to show.
+	 *
+	 * @since 4.9.0
+	 * @access protected
+	 *
+	 * @param array $instance Widget instance props.
+	 * @return bool Whether widget has content.
+	 */
+	protected function has_content( $instance ) {
+		if ( ! empty( $instance['ids'] ) ) {
+			$attachments = wp_parse_id_list( $instance['ids'] );
+			foreach ( $attachments as $attachment ) {
+				if ( 'attachment' !== get_post_type( $attachment ) ) {
+					return false;
+				}
+			}
+			return true;
+		}
+		return false;
+	}
+}
diff --git a/src/wp-includes/widgets/class-wp-widget-media.php b/src/wp-includes/widgets/class-wp-widget-media.php
index 84c9b3ff92..854cf885ae 100644
--- a/src/wp-includes/widgets/class-wp-widget-media.php
+++ b/src/wp-includes/widgets/class-wp-widget-media.php
@@ -257,6 +257,12 @@ abstract class WP_Widget_Media extends WP_Widget {
 				continue;
 			}
 			$value = $new_instance[ $field ];
+
+			// Workaround for rest_validate_value_from_schema() due to the fact that rest_is_boolean( '' ) === false, while rest_is_boolean( '1' ) is true.
+			if ( 'boolean' === $field_schema['type'] && '' === $value ) {
+				$value = false;
+			}
+
 			if ( true !== rest_validate_value_from_schema( $value, $field_schema, $field ) ) {
 				continue;
 			}
@@ -316,7 +322,7 @@ abstract class WP_Widget_Media extends WP_Widget {
 				class="media-widget-instance-property"
 				name="<?php echo esc_attr( $this->get_field_name( $name ) ); ?>"
 				id="<?php echo esc_attr( $this->get_field_id( $name ) ); // Needed specifically by wpWidgets.appendTitle(). ?>"
-				value="<?php echo esc_attr( strval( $value ) ); ?>"
+				value="<?php echo esc_attr( is_array( $value ) ? join( ',', $value ) : strval( $value ) ); ?>"
 			/>
 		<?php
 		endforeach;
@@ -388,7 +394,7 @@ abstract class WP_Widget_Media extends WP_Widget {
 				<label for="{{ elementIdPrefix }}title"><?php esc_html_e( 'Title:' ); ?></label>
 				<input id="{{ elementIdPrefix }}title" type="text" class="widefat title">
 			</p>
-			<div class="media-widget-preview">
+			<div class="media-widget-preview <?php echo esc_attr( $this->id_base ); ?>">
 				<div class="attachment-media-view">
 					<div class="placeholder"><?php echo esc_html( $this->l10n['no_media_selected'] ); ?></div>
 				</div>
diff --git a/tests/phpunit/tests/widgets/media-gallery-widget.php b/tests/phpunit/tests/widgets/media-gallery-widget.php
new file mode 100644
index 0000000000..0a6defaee4
--- /dev/null
+++ b/tests/phpunit/tests/widgets/media-gallery-widget.php
@@ -0,0 +1,201 @@
+<?php
+/**
+ * Unit tests covering WP_Widget_Media_Gallery functionality.
+ *
+ * @package    WordPress
+ * @subpackage widgets
+ */
+
+/**
+ * Test wp-includes/widgets/class-wp-widget-gallery.php
+ *
+ * @group widgets
+ */
+class Test_WP_Widget_Media_Gallery extends WP_UnitTestCase {
+
+	/**
+	 * Clean up global scope.
+	 *
+	 * @global WP_Scripts $wp_scripts
+	 * @global WP_Styles $wp_styles
+	 */
+	public function clean_up_global_scope() {
+		global $wp_scripts, $wp_styles;
+		parent::clean_up_global_scope();
+		$wp_scripts = null;
+		$wp_styles = null;
+	}
+
+	/**
+	 * Test get_instance_schema method.
+	 *
+	 * @covers WP_Widget_Media_Gallery::get_instance_schema()
+	 */
+	public function test_get_instance_schema() {
+		$widget = new WP_Widget_Media_Gallery();
+		$schema = $widget->get_instance_schema();
+
+		$this->assertEqualSets(
+			array(
+				'title',
+				'ids',
+				'columns',
+				'size',
+				'link_type',
+				'orderby_random',
+			),
+			array_keys( $schema )
+		);
+	}
+
+	/**
+	 * Test update() method.
+	 *
+	 * @covers WP_Widget_Media_Gallery::render_media()
+	 */
+	public function test_render_media() {
+		$widget = new WP_Widget_Media_Gallery();
+
+		$attachments = array();
+		foreach ( array( 'canola.jpg', 'waffles.jpg' ) as $filename ) {
+			$test_image = '/tmp/' . $filename;
+			copy( DIR_TESTDATA . '/images/canola.jpg', $test_image );
+			$attachment_id = self::factory()->attachment->create_object( array(
+				'file' => $test_image,
+				'post_parent' => 0,
+				'post_mime_type' => 'image/jpeg',
+				'post_title' => 'Canola',
+			) );
+			wp_update_attachment_metadata( $attachment_id, wp_generate_attachment_metadata( $attachment_id, $test_image ) );
+			$attachments[ $filename ] = $attachment_id;
+		}
+
+		$instance = wp_list_pluck( $widget->get_instance_schema(), 'default' );
+		$instance['size'] = 'thumbnail';
+		$instance['columns'] = 3;
+		$instance['ids'] = array_values( $attachments );
+		ob_start();
+		$widget->render_media( $instance );
+		$output = ob_get_clean();
+
+		$this->assertContains( 'gallery-columns-3', $output );
+		$this->assertContains( 'gallery-size-thumbnail', $output );
+		$this->assertContains( 'canola', $output );
+		$this->assertContains( 'waffles', $output );
+	}
+
+	/**
+	 * Test enqueue_admin_scripts() method.
+	 *
+	 * @covers WP_Widget_Media_Gallery::enqueue_admin_scripts()
+	 */
+	public function test_enqueue_admin_scripts() {
+		set_current_screen( 'widgets.php' );
+		$widget = new WP_Widget_Media_Gallery();
+
+		$this->assertFalse( wp_script_is( 'media-gallery-widget' ) );
+
+		$widget->enqueue_admin_scripts();
+
+		$this->assertTrue( wp_script_is( 'media-gallery-widget' ) );
+
+		$after = join( '', wp_scripts()->registered['media-gallery-widget']->extra['after'] );
+		$this->assertContains( 'wp.mediaWidgets.modelConstructors[ "media_gallery" ].prototype', $after );
+	}
+
+	/**
+	 * Test update() method.
+	 *
+	 * @covers WP_Widget_Media_Gallery::update()
+	 */
+	public function test_update() {
+		$widget = new WP_Widget_Media_Gallery();
+		$schema = $widget->get_instance_schema();
+		$instance = wp_list_pluck( $schema, 'default' );
+
+		// Field: title.
+		$instance['title'] = 'Hello <b>World</b> ';
+		$instance = $widget->update( $instance, array() );
+		$this->assertEquals( 'Hello World', $instance['title'] );
+
+		// Field: ids.
+		$instance['ids'] = '1,2,3';
+		$instance = $widget->update( $instance, array() );
+		$this->assertSame( array( 1, 2, 3 ), $instance['ids'] );
+
+		$instance['ids'] = array( 1, 2, '3' );
+		$instance = $widget->update( $instance, array() );
+		$this->assertSame( array( 1, 2, 3 ), $instance['ids'] );
+
+		$instance['ids'] = array( 'too', 'bad' );
+		$instance = $widget->update( $instance, array( 'ids' => array( 2, 3 ) ) );
+		$this->assertSame( array( 2, 3 ), $instance['ids'] );
+
+		// Field: columns.
+		$instance['columns'] = 4;
+		$instance = $widget->update( $instance, array() );
+		$this->assertSame( 4, $instance['columns'] );
+
+		$instance['columns'] = '2';
+		$instance = $widget->update( $instance, array() );
+		$this->assertSame( 2, $instance['columns'] );
+
+		$instance['columns'] = -1; // Under min of 1.
+		$instance = $widget->update( $instance, array( 'columns' => 3 ) );
+		$this->assertSame( 3, $instance['columns'] );
+
+		$instance['columns'] = 10; // Over max of 9.
+		$instance = $widget->update( $instance, array( 'columns' => 3 ) );
+		$this->assertSame( 3, $instance['columns'] );
+
+		// Field: size.
+		$instance['size'] = 'large';
+		$instance = $widget->update( $instance, array() );
+		$this->assertSame( 'large', $instance['size'] );
+
+		$instance['size'] = 'bad';
+		$instance = $widget->update( $instance, array( 'size' => 'thumbnail' ) );
+		$this->assertSame( 'thumbnail', $instance['size'] );
+
+		// Field: link_type.
+		$instance['link_type'] = 'none';
+		$instance = $widget->update( $instance, array() );
+		$this->assertSame( 'none', $instance['link_type'] );
+
+		$instance['link_type'] = 'unknown';
+		$instance = $widget->update( $instance, array( 'link_type' => 'file' ) );
+		$this->assertSame( 'file', $instance['link_type'] );
+
+		// Field: orderby_random.
+		$instance['orderby_random'] = '1';
+		$instance = $widget->update( $instance, array() );
+		$this->assertTrue( $instance['orderby_random'] );
+
+		$instance['orderby_random'] = true;
+		$instance = $widget->update( $instance, array() );
+		$this->assertTrue( $instance['orderby_random'] );
+
+		$instance['orderby_random'] = '';
+		$instance = $widget->update( $instance, array() );
+		$this->assertFalse( $instance['orderby_random'] );
+
+		$instance['orderby_random'] = false;
+		$instance = $widget->update( $instance, array() );
+		$this->assertFalse( $instance['orderby_random'] );
+	}
+
+	/**
+	 * Test render_control_template_scripts() method.
+	 *
+	 * @covers WP_Widget_Media_Gallery::render_control_template_scripts()
+	 */
+	public function test_render_control_template_scripts() {
+		$widget = new WP_Widget_Media_Gallery();
+
+		ob_start();
+		$widget->render_control_template_scripts();
+		$output = ob_get_clean();
+
+		$this->assertContains( '<script type="text/html" id="tmpl-wp-media-widget-gallery-preview">', $output );
+	}
+}
diff --git a/tests/qunit/index.html b/tests/qunit/index.html
index 52f8f8d789..d096aeeec7 100644
--- a/tests/qunit/index.html
+++ b/tests/qunit/index.html
@@ -119,6 +119,13 @@
 			wp.mediaWidgets.controlConstructors[ "media_audio" ].prototype.mime_type = "audio";
 			_.extend( wp.mediaWidgets.controlConstructors[ "media_audio" ].prototype.l10n, {"no_media_selected":"No audio selected","select_media":"Select File","change_media":"Change Audio","edit_media":"Edit Audio","add_to_widget":"Add to Widget","missing_attachment":"We can&#8217;t find that audio file. Check your <a href=\"http:\/\/src.wordpress-develop.dev\/wp-admin\/upload.php\">media library<\/a> and make sure it wasn&#8217;t deleted.","media_library_state_multi":{"0":"Audio Widget (%d)","1":"Audio Widget (%d)","singular":"Audio Widget (%d)","plural":"Audio Widget (%d)","context":null,"domain":null},"media_library_state_single":"Audio Widget"} );
 		</script>
+		<script type='text/javascript' src='../../src/wp-admin/js/widgets/media-gallery-widget.js'></script>
+		<script type='text/javascript'>
+			wp.mediaWidgets.modelConstructors[ "media_gallery" ].prototype.schema = {"title":{"type":"string","default":"","should_preview_update":false},"ids":{"type":"string","default":""},"columns":{"type":"integer","default":3},"size":{"type":"string","default":"thumbnail","enum":["thumbnail","medium","medium_large","large","post-thumbnail","full","custom"]},"link_type":{"type":"string","default":"none","enum":["none","file","post"],"media_prop":"link","should_preview_update":false},"orderby_random":{"type":"boolean","default":false,"media_prop":"_orderbyRandom","should_preview_update":false},"attachments":{"type":"string","default":""}};
+			wp.mediaWidgets.controlConstructors[ "media_gallery" ].prototype.mime_type = "image";
+
+			_.extend( wp.mediaWidgets.controlConstructors[ "media_gallery" ].prototype.l10n, {"no_media_selected":"No images selected","add_media":"Add Media","replace_media":"Replace Media","edit_media":"Edit Gallery","add_to_widget":"Add to Widget","missing_attachment":"We can&#8217;t find that gallery. Check your <a href=\"http:\/\/src.wordpress-develop.dev\/wp-admin\/upload.php\">media library<\/a> and make sure it wasn&#8217;t deleted.","media_library_state_multi":"","media_library_state_single":"","unsupported_file_type":"Looks like this isn&#8217;t the correct kind of file. Please link to an appropriate file instead.","select_media":"Select Images","change_media":"Add Image"} );
+		</script>
 
 		<!-- Unit tests -->
 		<script src="wp-admin/js/password-strength-meter.js"></script>
@@ -136,6 +143,7 @@
 		<script src="wp-admin/js/nav-menu.js"></script>
 		<script src="wp-admin/js/widgets/test-media-widgets.js"></script>
 		<script src="wp-admin/js/widgets/test-media-image-widget.js"></script>
+		<script src="wp-admin/js/widgets/test-media-gallery-widget.js"></script>
 		<script src="wp-admin/js/widgets/test-media-video-widget.js"></script>
 
 		<!-- Customizer templates for sections -->
@@ -569,7 +577,7 @@
 					</div><!-- #available-widgets-list -->
 				</div><!-- #available-widgets -->
 			</div><!-- #widgets-left -->
-			
+
 			<script type="text/html" id="tmpl-widget-media-media_image-control">
 			<# var elementIdPrefix = 'el' + String( Math.random() ) + '_' #>
 			<p>
@@ -811,6 +819,60 @@
 		<div class="media-frame-uploader"></div>
 	</script>
 
+	<script type="text/html" id="tmpl-widget-media-media_gallery-control">
+		<# var elementIdPrefix = 'el' + String( Math.random() ) + '_' #>
+		<p>
+			<label for="{{ elementIdPrefix }}title">Title:</label>
+			<input id="{{ elementIdPrefix }}title" type="text" class="widefat title">
+		</p>
+		<div class="media-widget-preview">
+			<div class="attachment-media-view">
+				<div class="placeholder">No images selected</div>
+			</div>
+			</div>
+			<p class="media-widget-buttons">
+				<button type="button" class="button edit-media selected">
+					Edit Gallery				</button>
+				<button type="button" class="button change-media select-media selected">
+					Replace Media				</button>
+				<button type="button" class="button select-media not-selected">
+					Add Media				</button>
+			</p>
+		<div class="media-widget-fields">
+		</div>
+	</script>
+				<script type="text/html" id="tmpl-wp-media-widget-gallery-preview">
+			<# var describedById = 'describedBy-' + String( Math.random() ); #>
+			<# data.attachments = data.attachments ? JSON.parse(data.attachments) : ''; #>
+			<# if ( Array.isArray( data.attachments ) && data.attachments.length ) { #>
+				<div class="gallery gallery-columns-{{ data.columns }}">
+					<# _.each( data.attachments, function( attachment, index ) { #>
+						<dl class="gallery-item">
+							<dt class="gallery-icon">
+							<# if ( attachment.sizes.thumbnail ) { #>
+								<img src="{{ attachment.sizes.thumbnail.url }}" width="{{ attachment.sizes.thumbnail.width }}" height="{{ attachment.sizes.thumbnail.height }}" alt="" />
+							<# } else { #>
+								<img src="{{ attachment.url }}" alt="" />
+							<# } #>
+							</dt>
+							<# if ( attachment.caption ) { #>
+								<dd class="wp-caption-text gallery-caption">
+									{{{ data.verifyHTML( attachment.caption ) }}}
+								</dd>
+							<# } #>
+						</dl>
+						<# if ( index % data.columns === data.columns - 1 ) { #>
+							<br style="clear: both;">
+						<# } #>
+					<# } ); #>
+				</div>
+			<# } else { #>
+				<div class="attachment-media-view">
+					<p class="placeholder">No images selected</p>
+				</div>
+			<# } #>
+		</script>
+
 	<script type="text/html" id="tmpl-media-modal">
 		<div class="media-modal wp-core-ui">
 			<button type="button" class="media-modal-close"><span class="media-modal-icon"><span class="screen-reader-text">Close media panel</span></span></button>
diff --git a/tests/qunit/wp-admin/js/widgets/test-media-gallery-widget.js b/tests/qunit/wp-admin/js/widgets/test-media-gallery-widget.js
new file mode 100644
index 0000000000..c07dae52d8
--- /dev/null
+++ b/tests/qunit/wp-admin/js/widgets/test-media-gallery-widget.js
@@ -0,0 +1,30 @@
+/* global wp */
+/* jshint qunit: true */
+/* eslint-env qunit */
+/* eslint-disable no-magic-numbers */
+
+( function() {
+	'use strict';
+
+	module( 'Gallery Media Widget' );
+
+	test( 'gallery widget control', function() {
+		var GalleryWidgetControl;
+		equal( typeof wp.mediaWidgets.controlConstructors.media_gallery, 'function', 'wp.mediaWidgets.controlConstructors.media_gallery is a function' );
+		GalleryWidgetControl = wp.mediaWidgets.controlConstructors.media_gallery;
+		ok( GalleryWidgetControl.prototype instanceof wp.mediaWidgets.MediaWidgetControl, 'wp.mediaWidgets.controlConstructors.media_gallery subclasses wp.mediaWidgets.MediaWidgetControl' );
+	});
+
+	test( 'gallery media model', function() {
+		var GalleryWidgetModel, galleryWidgetModelInstance;
+		equal( typeof wp.mediaWidgets.modelConstructors.media_gallery, 'function', 'wp.mediaWidgets.modelConstructors.media_gallery is a function' );
+		GalleryWidgetModel = wp.mediaWidgets.modelConstructors.media_gallery;
+		ok( GalleryWidgetModel.prototype instanceof wp.mediaWidgets.MediaWidgetModel, 'wp.mediaWidgets.modelConstructors.media_gallery subclasses wp.mediaWidgets.MediaWidgetModel' );
+
+		galleryWidgetModelInstance = new GalleryWidgetModel();
+		_.each( galleryWidgetModelInstance.attributes, function( value, key ) {
+			equal( value, GalleryWidgetModel.prototype.schema[ key ][ 'default' ], 'Should properly set default for ' + key );
+		});
+	});
+
+})();