#1451: Detect grid direction

Sortable.js

@@ -121,23 +121,34 @@
 
 		_detectDirection = function(el, options) {
 			var elCSS = _css(el),
-				elWidth = parseInt(elCSS.width),
+				elWidth = parseInt(elCSS.width)
+					- parseInt(elCSS.paddingLeft)
+					- parseInt(elCSS.paddingRight)
+					- parseInt(elCSS.borderLeftWidth)
+					- parseInt(elCSS.borderRightWidth),
 				child1 = _getChild(el, 0, options),
 				child2 = _getChild(el, 1, options),
 				firstChildCSS = child1 && _css(child1),
 				secondChildCSS = child2 && _css(child2),
 				firstChildWidth = firstChildCSS && parseInt(firstChildCSS.marginLeft) + parseInt(firstChildCSS.marginRight) + _getRect(child1).width,
 				secondChildWidth = secondChildCSS && parseInt(secondChildCSS.marginLeft) + parseInt(secondChildCSS.marginRight) + _getRect(child2).width;
+
 			if (elCSS.display === 'flex') {
 				return elCSS.flexDirection === 'column' || elCSS.flexDirection === 'column-reverse'
 				? 'vertical' : 'horizontal';
 			}
+
+			if (elCSS.display === 'grid') {
+				return elCSS.gridTemplateColumns.split(' ').length <= 1 ? 'vertical' : 'horizontal';
+			}
+
 			if (child1 && firstChildCSS.float !== 'none') {
 				var touchingSideChild2 = firstChildCSS.float === 'left' ? 'left' : 'right';
 
 				return child2 && (secondChildCSS.clear === 'both' || secondChildCSS.clear === touchingSideChild2) ?
 					'vertical' : 'horizontal';
 			}
+
 			return (child1 &&
 				(
 					firstChildCSS.display === 'block' ||