wpLink: add keyboard navigation, improve accessibility. Props afercia, fixes #28897.

Built from https://develop.svn.wordpress.org/trunk@29321


git-svn-id: http://core.svn.wordpress.org/trunk@29102 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/js/wplink.js

@@ -31,6 +31,11 @@ var wpLink;
 			rivers.recent = new River( $( '#most-recent-results' ) );
 			rivers.elements = inputs.dialog.find( '.query-results' );
 
+			// Get search notice text
+			inputs.queryNotice = $( '#query-notice-message' );
+			inputs.queryNoticeTextDefault = inputs.queryNotice.find( '.query-notice-default' );
+			inputs.queryNoticeTextHint = inputs.queryNotice.find( '.query-notice-hint' );
+
 			// Bind event handlers
 			inputs.dialog.keydown( wpLink.keydown );
 			inputs.dialog.keyup( wpLink.keyup );
@@ -43,10 +48,19 @@ var wpLink;
 				wpLink.close();
 			});
 
-			$( '#wp-link-search-toggle' ).click( wpLink.toggleInternalLinking );
+			$( '#wp-link-search-toggle' ).on( 'click', wpLink.toggleInternalLinking );
 
 			rivers.elements.on( 'river-select', wpLink.updateFields );
 
+			// Display 'hint' message when search field or 'query-results' box are focused
+			inputs.search.add( rivers.elements ).on( 'focus.wplink', function() {
+				inputs.queryNoticeTextDefault.hide();
+				inputs.queryNoticeTextHint.removeClass( 'screen-reader-text' ).show();
+			} ).on( 'blur.wplink', function() {
+				inputs.queryNoticeTextDefault.show();
+				inputs.queryNoticeTextHint.addClass( 'screen-reader-text' ).hide();
+			} );
+
 			inputs.search.keyup( function() {
 				var self = this;
 
@@ -335,6 +349,8 @@ var wpLink;
 			} else if ( key.TAB === event.keyCode ) {
 				id = event.target.id;
 
+				// wp-link-submit must always be the last focusable element in the dialog.
+				// following focusable elements will be skipped on keyboard navigation.
 				if ( id === 'wp-link-submit' && ! event.shiftKey ) {
 					inputs.close.focus();
 					event.preventDefault();
@@ -391,12 +407,13 @@ var wpLink;
 			};
 		},
 
-		toggleInternalLinking: function() {
+		toggleInternalLinking: function( event ) {
 			var visible = inputs.wrap.hasClass( 'search-panel-visible' );
 
 			inputs.wrap.toggleClass( 'search-panel-visible', ! visible );
 			setUserSetting( 'wplink', visible ? '0' : '1' );
 			inputs[ ! visible ? 'search' : 'url' ].focus();
+			event.preventDefault();
 		}
 	};
 
@@ -506,7 +523,7 @@ var wpLink;
 
 			if ( ! results ) {
 				if ( firstPage ) {
-					list += '<li class="unselectable"><span class="item-title"><em>' +
+					list += '<li class="unselectable no-matches-found"><span class="item-title"><em>' +
 						wpLinkL10n.noMatchesFound + '</em></span></li>';
 				}
 			} else {