Administration: Remove deprecated unload event handlers and use pagehide (and pageshow) when appropriate.

Use `pagehide` event instead of `unload` in the following cases:

* For classic editor to release the post lock.
* In Text widget to rebuild editor after dragging widget to new location in classic widgets interface.
* To clear out the `window.name` when navigating away from a post preview.
* To suspend heartbeat, while also using `pageshow` event to resume as if it had been a focused tab in case page restored from bfcache. 

Also:

* Remove obsolete mobile cleanup code in `js/_enqueues/lib/gallery.js` (introduced in [9894]). Do same for `src/js/_enqueues/wp/media/models.js` (introduced in [22872]). See #22552.
* Remove obsolete Firefox-specific workaround in `js/_enqueues/wp/mce-view.js` from [39282]. See #38511.

Fixes #55491.
Props spenserhale, westonruter, adamsilverstein, azaozz, shawfactor, peterwilsoncc, swissspidy.

git-svn-id: https://develop.svn.wordpress.org/trunk@56809 602fd350-edb4-49c9-b593-d223f7449a82

src/js/_enqueues/admin/post.js

@@ -511,7 +511,7 @@ jQuery( function($) {
 			// See https://developer.mozilla.org/en-US/docs/Web/API/Window/beforeunload_event.
 			return __( 'The changes you made will be lost if you navigate away from this page.' );
 		}
-	}).on( 'unload.edit-post', function( event ) {
+	}).on( 'pagehide.edit-post', function( event ) {
 		if ( ! releaseLock ) {
 			return;
 		}

src/js/_enqueues/lib/gallery.js

@@ -88,8 +88,6 @@ jQuery( function($) {
 	}
 });
 
-jQuery(window).on( 'unload', function () { window.tinymce = window.tinyMCE = window.wpgallery = null; } ); // Cleanup.
-
 /* gallery settings */
 window.tinymce = null;
 

src/js/_enqueues/wp/heartbeat.js

@@ -223,9 +223,9 @@
 				settings.checkFocusTimer = window.setInterval( checkFocus, 10000 );
 			}
 
-			$(window).on( 'unload.wp-heartbeat', function() {
+			$(window).on( 'pagehide.wp-heartbeat', function() {
 				// Don't connect anymore.
-				settings.suspend = true;
+				suspend();
 
 				// Abort the last request if not completed.
 				if ( settings.xhr && settings.xhr.readyState !== 4 ) {
@@ -233,6 +233,25 @@
 				}
 			});
 
+			$(window).on(
+				'pageshow.wp-heartbeat',
+				/**
+				 * Handles pageshow event, specifically when page navigation is restored from back/forward cache.
+				 *
+				 * @param {jQuery.Event} event
+				 * @param {PageTransitionEvent} event.originalEvent
+				 */
+				function ( event ) {
+					if ( event.originalEvent.persisted ) {
+						/*
+						 * When page navigation is stored via bfcache (Back/Forward Cache), consider this the same as
+						 * if the user had just switched to the tab since the behavior is similar.
+						 */
+						focused();
+					}
+				}
+			);
+
 			// Check for user activity every 30 seconds.
 			window.setInterval( checkUserActivity, 30000 );
 
@@ -541,7 +560,7 @@
 			settings.userActivity = time();
 
 			// Resume if suspended.
-			settings.suspend = false;
+			resume();
 
 			if ( ! settings.hasFocus ) {
 				settings.hasFocus = true;
@@ -549,6 +568,20 @@
 			}
 		}
 
+		/**
+		 * Suspends connecting.
+		 */
+		function suspend() {
+			settings.suspend = true;
+		}
+
+		/**
+		 * Resumes connecting.
+		 */
+		function resume() {
+			settings.suspend = false;
+		}
+
 		/**
 		 * Runs when the user becomes active after a period of inactivity.
 		 *
@@ -593,7 +626,7 @@
 			// Suspend after 10 minutes of inactivity when suspending is enabled.
 			// Always suspend after 60 minutes of inactivity. This will release the post lock, etc.
 			if ( ( settings.suspendEnabled && lastActive > 600000 ) || lastActive > 3600000 ) {
-				settings.suspend = true;
+				suspend();
 			}
 
 			if ( ! settings.userActivityEvents ) {

src/js/_enqueues/wp/mce-view.js

@@ -643,16 +643,6 @@
 					}, 3000 );
 				}
 
-				function reload() {
-					if ( ! editor.isHidden() ) {
-						$( node ).data( 'rendered', null );
-
-						setTimeout( function() {
-							wp.mce.views.render();
-						} );
-					}
-				}
-
 				function addObserver() {
 					observer = new MutationObserver( _.debounce( resize, 100 ) );
 
@@ -663,7 +653,7 @@
 					} );
 				}
 
-				$( iframeWin ).on( 'load', resize ).on( 'unload', reload );
+				$( iframeWin ).on( 'load', resize );
 
 				MutationObserver = iframeWin.MutationObserver || iframeWin.WebKitMutationObserver || iframeWin.MozMutationObserver;
 

src/js/_enqueues/wp/media/models.js

@@ -2,8 +2,7 @@
  * @output wp-includes/js/media-models.js
  */
 
-var $ = jQuery,
-	Attachment, Attachments, l10n, media;
+var Attachment, Attachments, l10n, media;
 
 /** @namespace wp */
 window.wp = window.wp || {};
@@ -237,8 +236,3 @@ media.query = function( props ) {
 		props: _.extend( _.defaults( props || {}, { orderby: 'date' } ), { query: true } )
 	});
 };
-
-// Clean up. Prevents mobile browsers caching.
-$(window).on('unload', function(){
-	window.wp = null;
-});

src/js/_enqueues/wp/widgets/text.js

@@ -291,7 +291,7 @@ wp.textWidgets = ( function( $ ) {
 				onInit = function() {
 
 					// When a widget is moved in the DOM the dynamically-created TinyMCE iframe will be destroyed and has to be re-built.
-					$( editor.getWin() ).on( 'unload', function() {
+					$( editor.getWin() ).on( 'pagehide', function() {
 						_.defer( buildEditor );
 					});
 

src/wp-includes/functions.php

@@ -7585,7 +7585,7 @@ function wp_delete_file_from_directory( $file, $directory ) {
 }
 
 /**
- * Outputs a small JS snippet on preview tabs/windows to remove `window.name` on unload.
+ * Outputs a small JS snippet on preview tabs/windows to remove `window.name` when a user is navigating to another page.
  *
  * This prevents reusing the same tab for a preview when the user has navigated away.
  *
@@ -7614,7 +7614,7 @@ function wp_post_preview_js() {
 		}
 
 		if ( window.addEventListener ) {
-			window.addEventListener( 'unload', function() { window.name = ''; }, false );
+			window.addEventListener( 'pagehide', function() { window.name = ''; } );
 		}
 	}());
 	</script>