Selectable: proper handling of inner scrolling

Fixes #13359

Author: bleshik

ui/selectable.js

@@ -61,7 +61,7 @@ return $.widget("ui.selectable", $.ui.mouse, {
 			that._addClass( that.selectees, "ui-selectee" );
 			that.selectees.each(function() {
 				var $this = $(this),
-					pos = $this.offset();
+					pos = $this.position();
 				$.data(this, "selectable-item", {
 					element: this,
 					$element: $this,
@@ -94,6 +94,7 @@ return $.widget("ui.selectable", $.ui.mouse, {
 			options = this.options;
 
 		this.opos = [ event.pageX, event.pageY ];
+		this.elementPos = $(this.element[0]).offset();
 
 		if (this.options.disabled) {
 			return;
@@ -180,16 +181,22 @@ return $.widget("ui.selectable", $.ui.mouse, {
 		this.selectees.each(function() {
 			var selectee = $.data(this, "selectable-item"),
 				hit = false;
+			var offset = {
+				left: selectee.left + that.elementPos.left,
+				right: selectee.right + that.elementPos.left,
+				top: selectee.top + that.elementPos.top,
+				bottom: selectee.bottom + that.elementPos.top
+			}
 
 			//prevent helper from being selected if appendTo: selectable
 			if (!selectee || selectee.element === that.element[0]) {
 				return;
 			}
 
 			if (options.tolerance === "touch") {
-				hit = ( !(selectee.left > x2 || selectee.right < x1 || selectee.top > y2 || selectee.bottom < y1) );
+				hit = ( !(offset.left > x2 || offset.right < x1 || offset.top > y2 || offset.bottom < y1) );
 			} else if (options.tolerance === "fit") {
-				hit = (selectee.left > x1 && selectee.right < x2 && selectee.top > y1 && selectee.bottom < y2);
+				hit = (offset.left > x1 && offset.right < x2 && offset.top > y1 && offset.bottom < y2);
 			}
 
 			if (hit) {