Customize: Allow tab characters in custom CSS input.

Pressing `Esc` followed by `Tab` allows for tabbing to the next element.

Props afercia, coffee2code, westonruter.
See #35395.
Fixes #38667.


git-svn-id: https://develop.svn.wordpress.org/trunk@39149 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/css/customize-controls.css

@@ -1129,6 +1129,10 @@ p.customize-section-description {
 	margin-left: 10px;
 	margin-right: 10px;
 }
+#customize-theme-controls #sub-accordion-section-custom_css textarea {
+	-moz-tab-size: 4;
+	tab-size: 4;
+}
 
 #sub-accordion-section-custom_css .customize-control-notifications-container {
 	margin-bottom: 15px;

src/wp-admin/js/customize-controls.js

@@ -5234,6 +5234,53 @@
 			});
 		});
 
+		// Allow tabs to be entered in Custom CSS textarea.
+		api.control( 'custom_css', function setupCustomCssControl( control ) {
+			control.deferred.embedded.done( function allowTabs() {
+				var $textarea = control.container.find( 'textarea' ), textarea = $textarea[0];
+
+				$textarea.on( 'blur', function onBlur() {
+					$textarea.data( 'next-tab-blurs', false );
+				} );
+
+				$textarea.on( 'keydown', function onKeydown( event ) {
+					var selectionStart, selectionEnd, value, scroll, tabKeyCode = 9, escKeyCode = 27;
+
+					if ( escKeyCode === event.keyCode ) {
+						if ( ! $textarea.data( 'next-tab-blurs' ) ) {
+							$textarea.data( 'next-tab-blurs', true );
+							event.stopPropagation(); // Prevent collapsing the section.
+						}
+						return;
+					}
+
+					// Short-circuit if tab key is not being pressed or if a modifier key *is* being pressed.
+					if ( tabKeyCode !== event.keyCode || event.ctrlKey || event.altKey || event.shiftKey ) {
+						return;
+					}
+
+					// Prevent capturing Tab characters if Esc was pressed.
+					if ( $textarea.data( 'next-tab-blurs' ) ) {
+						return;
+					}
+
+					selectionStart = textarea.selectionStart;
+					selectionEnd = textarea.selectionEnd;
+					value = textarea.value;
+
+					if ( selectionStart >= 0 ) {
+						scroll = $textarea.scrollTop;
+						textarea.value = value.substring( 0, selectionStart ).concat( '\t', value.substring( selectionEnd ) );
+						$textarea.selectionStart = textarea.selectionEnd = selectionStart + 1;
+						textarea.scrollTop = scroll;
+					}
+
+					event.stopPropagation();
+					event.preventDefault();
+				} );
+			} );
+		} );
+
 		// Update the setting validities.
 		api.previewer.bind( 'selective-refresh-setting-validities', function handleSelectiveRefreshedSettingValidities( settingValidities ) {
 			api._handleSettingValidities( {

src/wp-includes/class-wp-customize-manager.php

@@ -3590,7 +3590,7 @@ final class WP_Customize_Manager {
 			'priority'           => 200,
 			'description_hidden' => true,
 			'description'        => sprintf( '%s<br /><a href="%s" class="external-link" target="_blank">%s<span class="screen-reader-text">%s</span></a>',
-				__( 'CSS allows you to customize the appearance and layout of your site with code. Separate CSS is saved for each of your themes.' ),
+				__( 'CSS allows you to customize the appearance and layout of your site with code. Separate CSS is saved for each of your themes. In the editing area the Tab key enters a tab character. To move below this area by pressing Tab, press the Esc key followed by the Tab key.' ),
 				'https://codex.wordpress.org/Know_Your_Sources#CSS',
 				__( 'Learn more about CSS' ),
 				__( '(link opens in a new window)' )