Dialog: Add option to put the dialog title in a header element

Implement a new option: `uiDialogTitleHeadingLevel`, allowing to change
the `span` wrapping the dialog title into a heading element (`h1`-`h6`).
Value `0` represents the `span`, values 1-6 - a heading at the specified
level.

Fixes gh-2271
Closes gh-2275

tests/unit/dialog/common-deprecated.js

@@ -34,6 +34,7 @@ common.testWidget( "dialog", {
 		resizable: true,
 		show: null,
 		title: null,
+		uiDialogTitleHeadingLevel: 0,
 		width: 300,
 
 		// Callbacks

tests/unit/dialog/common.js

@@ -33,6 +33,7 @@ common.testWidget( "dialog", {
 		resizable: true,
 		show: null,
 		title: null,
+		uiDialogTitleHeadingLevel: 0,
 		width: 300,
 
 		// Callbacks

tests/unit/dialog/core.js

@@ -117,6 +117,44 @@ QUnit.test( "aria-modal", function( assert ) {
 	element.remove();
 } );
 
+QUnit.test( "ui dialog title heading level", function( assert ) {
+	assert.expect( 8 );
+
+	var element, nodeName;
+
+	element = $( "<div>" ).dialog( { modal: true } );
+	nodeName = element.dialog( "widget" ).find( ".ui-dialog-title" ).get( 0 ).nodeName.toLowerCase();
+	assert.equal( nodeName, "span", "Element wrapping the dialog title is span" );
+
+	element = $( "<div>" ).dialog( { modal: true, uiDialogTitleHeadingLevel: 0 } );
+	nodeName = element.dialog( "widget" ).find( ".ui-dialog-title" ).get( 0 ).nodeName.toLowerCase();
+	assert.equal( nodeName, "span", "Element wrapping the dialog title is span" );
+
+	element = $( "<div>" ).dialog( { modal: true, uiDialogTitleHeadingLevel: 1 } );
+	nodeName = element.dialog( "widget" ).find( ".ui-dialog-title" ).get( 0 ).nodeName.toLowerCase();
+	assert.equal( nodeName, "h1", "Element wrapping the dialog title is h1" );
+
+	element = $( "<div>" ).dialog( { modal: true, uiDialogTitleHeadingLevel: 6 } );
+	nodeName = element.dialog( "widget" ).find( ".ui-dialog-title" ).get( 0 ).nodeName.toLowerCase();
+	assert.equal( nodeName, "h6", "Element wrapping the dialog title is h6" );
+
+	element = $( "<div>" ).dialog( { modal: true, uiDialogTitleHeadingLevel: 9 } );
+	nodeName = element.dialog( "widget" ).find( ".ui-dialog-title" ).get( 0 ).nodeName.toLowerCase();
+	assert.equal( nodeName, "span", "Element wrapping the dialog title is span" );
+
+	element = $( "<div>" ).dialog( { modal: true, uiDialogTitleHeadingLevel: -9 } );
+	nodeName = element.dialog( "widget" ).find( ".ui-dialog-title" ).get( 0 ).nodeName.toLowerCase();
+	assert.equal( nodeName, "span", "Element wrapping the dialog title is span" );
+
+	element = $( "<div>" ).dialog( { modal: true, uiDialogTitleHeadingLevel: 2.3 } );
+	nodeName = element.dialog( "widget" ).find( ".ui-dialog-title" ).get( 0 ).nodeName.toLowerCase();
+	assert.equal( nodeName, "span", "Element wrapping the dialog title is span" );
+
+	element = $( "<div>" ).dialog( { modal: true, uiDialogTitleHeadingLevel: "foo" } );
+	nodeName = element.dialog( "widget" ).find( ".ui-dialog-title" ).get( 0 ).nodeName.toLowerCase();
+	assert.equal( nodeName, "span", "Element wrapping the dialog title is span" );
+} );
+
 QUnit.test( "widget method", function( assert ) {
 	assert.expect( 1 );
 	var dialog = $( "<div>" ).appendTo( "#qunit-fixture" ).dialog();

ui/widgets/dialog.js

@@ -81,6 +81,7 @@ $.widget( "ui.dialog", {
 		resizable: true,
 		show: null,
 		title: null,
+		uiDialogTitleHeadingLevel: 0,
 		width: 300,
 
 		// Callbacks
@@ -437,7 +438,13 @@ $.widget( "ui.dialog", {
 			}
 		} );
 
-		uiDialogTitle = $( "<span>" ).uniqueId().prependTo( this.uiDialogTitlebar );
+		var uiDialogHeadingLevel = Number.isInteger( this.options.uiDialogTitleHeadingLevel ) &&
+			this.options.uiDialogTitleHeadingLevel > 0 &&
+			this.options.uiDialogTitleHeadingLevel <= 6 ?
+			"h" + this.options.uiDialogTitleHeadingLevel : "span";
+
+		uiDialogTitle = $( "<" + uiDialogHeadingLevel + ">" )
+			.uniqueId().prependTo( this.uiDialogTitlebar );
 		this._addClass( uiDialogTitle, "ui-dialog-title" );
 		this._title( uiDialogTitle );