Port SortableJS#2245

Author: lofcz

src/Sortable.js

@@ -353,6 +353,10 @@ function Sortable(el, options) {
 	this.el = el; // root element
 	this.options = options = Object.assign({}, options);
 
+	if (this.options.fallbackOnBody) {
+		// backwards compatibility
+		this.options.getFallbackParent = () => (document.body)
+	}
 
 	// Export instance
 	el[expando] = this;
@@ -390,6 +394,7 @@ function Sortable(el, options) {
 		touchStartThreshold: (Number.parseInt ? Number : window).parseInt(window.devicePixelRatio, 10) || 1,
 		forceFallback: false,
 		fallbackClass: 'sortable-fallback',
+		getFallbackParent: null,
 		fallbackOnBody: false,
 		fallbackTolerance: 0,
 		fallbackOffset: {x: 0, y: 0},
@@ -852,7 +857,8 @@ Sortable.prototype = /** @lends Sortable.prototype */ {
 		// Bug if using scale(): https://stackoverflow.com/questions/2637058
 		// Not being adjusted for
 		if (!ghostEl) {
-			let container = this.options.fallbackOnBody ? document.body : rootEl,
+			let fallbackParent = typeof this.options.getFallbackParent === 'function' ? this.options.getFallbackParent() : null
+			let container = fallbackParent ?? rootEl,
 				rect = getRect(dragEl, true, PositionGhostAbsolutely, true, container),
 				options = this.options;
 

st/app.js

@@ -202,7 +202,7 @@ for (var i = 0; i < nestedSortables.length; i++) {
 	new Sortable(nestedSortables[i], {
 		group: 'nested',
 		animation: 150,
-		fallbackOnBody: true,
+		getFallbackParent: () => (document.body),
 		swapThreshold: 0.65
 	});
 }