Draggable: Only apply ui-draggable-handle within the draggable instance

Fixes #10212
Closes jquerygh-1284

Author: tjvantoll

tests/unit/draggable/draggable_core.js

@@ -274,15 +274,19 @@ asyncTest( "#4261: active element should blur when mousing down on a draggable",
 });
 
 test( "ui-draggable-handle assigned to appropriate element", function() {
-	expect( 4 );
+	expect( 5 );
 
-	var element = $( "<div><p></p></div>" ).appendTo( "#qunit-fixture" ).draggable();
+	var p = $( "<p>" ).appendTo( "#qunit-fixture" ),
+		element = $( "<div><p></p></div>" ).appendTo( "#qunit-fixture" ).draggable();
 	ok( element.hasClass( "ui-draggable-handle" ), "handle is element by default" );
 
 	element.draggable( "option", "handle", "p" );
 	ok( !element.hasClass( "ui-draggable-handle" ), "removed from element" );
 	ok( element.find( "p" ).hasClass( "ui-draggable-handle" ), "added to handle" );
 
+	ok( !p.hasClass( "ui-draggable-handle" ),
+		"ensure handle class name is constrained within the draggble (#10212)" );
+
 	element.draggable( "destroy" );
 	ok( !element.find( "p" ).hasClass( "ui-draggable-handle" ), "removed in destroy()" );
 });

ui/draggable.js

@@ -314,8 +314,10 @@ $.widget("ui.draggable", $.ui.mouse, {
 	},
 
 	_setHandleClassName: function() {
+		var handle =  this.options.handle ?
+			this.element.find( this.options.handle ) : this.element;
 		this._removeHandleClassName();
-		$( this.options.handle || this.element ).addClass( "ui-draggable-handle" );
+		handle.addClass( "ui-draggable-handle" );
 	},
 
 	_removeHandleClassName: function() {