Resizable: Fix resizing of elems with box-sizing: border-box

Fixes gh-1979
Closes gh-2012

tests/unit/resizable/options.js

@@ -532,4 +532,30 @@ QUnit.test( "alsoResize + multiple selection", function( assert ) {
 	assert.equal( other2.height(), 150, "alsoResize o2 constrained height at containment edge" );
 } );
 
+QUnit.test( "alsoResize with box-sizing: border-box", function( assert ) {
+	assert.expect( 4 );
+
+	var other = $( "<div>" )
+			.css( {
+				width: 50,
+				height: 50,
+				padding: 10,
+				border: 5
+			} )
+			.appendTo( "body" ),
+		element = $( "#resizable1" ).resizable( {
+			alsoResize: other
+		} ),
+		handle = ".ui-resizable-se";
+
+	$( "*" ).css( "box-sizing", "border-box" );
+
+	testHelper.drag( handle, 80, 80 );
+
+	assert.equal( element.width(), 180, "resizable width" );
+	assert.equal( parseFloat( other.css( "width" ) ), 130, "alsoResize width" );
+	assert.equal( element.height(), 180, "resizable height" );
+	assert.equal( parseFloat( other.css( "height" ) ), 130, "alsoResize height" );
+} );
+
 } );

ui/widgets/resizable.js

@@ -533,15 +533,18 @@ $.widget( "ui.resizable", $.ui.mouse, {
 		if ( this.position.left !== this.prevPosition.left ) {
 			props.left = this.position.left + "px";
 		}
+
+		this.helper.css( props );
+
 		if ( this.size.width !== this.prevSize.width ) {
 			props.width = this.size.width + "px";
+			this.helper.width( props.width );
 		}
 		if ( this.size.height !== this.prevSize.height ) {
 			props.height = this.size.height + "px";
+			this.helper.height( props.height );
 		}
 
-		this.helper.css( props );
-
 		return props;
 	},
 
@@ -1048,7 +1051,7 @@ $.ui.plugin.add( "resizable", "alsoResize", {
 		$( o.alsoResize ).each( function() {
 			var el = $( this );
 			el.data( "ui-resizable-alsoresize", {
-				width: parseFloat( el.width() ), height: parseFloat( el.height() ),
+				width: parseFloat( el.css( "width" ) ), height: parseFloat( el.css( "height" ) ),
 				left: parseFloat( el.css( "left" ) ), top: parseFloat( el.css( "top" ) )
 			} );
 		} );