added possibility to scroll Et2TreeDropdown on open to current selection.

-- set openAtSelection="true" attribute on the et2-tree-dropdown
-- use for timezone selection in preferences
-- regarding Ticket #97411

api/js/etemplate/Et2Tree/Et2Tree.ts

@@ -667,6 +667,59 @@ export class Et2Tree extends Et2WidgetWithSelectMixin(LitElement) implements Fin
 		item.focused = true
 	}
 
+	/**
+	 * scroll to item with given id
+	 * make sure all parents of the item are expanded else scroll will fail
+	 * @param _id
+	 */
+	public scrollToItem(_id: string)
+	{
+		const item: SlTreeItem = this.getDomNode(_id);
+		if (item == null) return
+		item.scrollIntoView();
+	}
+
+	/**
+	 * scrolls to the (first) selected slTreeItem into view
+	 * this function delays, if not all parents of the item are expanded
+	 *
+	 */
+	public scrollToSelected()
+	{
+		try
+		{
+			const item: SlTreeItem = this.shadowRoot.querySelector('sl-tree-item[selected]');
+			if (item == null) return
+
+
+			//this might not work because item pant is not expanded
+			//in that case expand all parents and wait before trying to scroll again
+			let parent: SlTreeItem = item.parentElement?.tagName === "SL-TREE-ITEM" ? <SlTreeItem>item.parentElement : null;
+			//scroll and exit if parent does not need expansion
+			if (!parent || parent.expanded)
+			{
+				item.scrollIntoView()
+				return
+			}
+			//fallback
+			//expand all parent items
+			while (parent)
+			{
+				if (!parent.expanded) parent.expanded = true;
+				parent = parent.parentElement?.tagName === "SL-TREE-ITEM" ? <SlTreeItem>parent.parentElement : null;
+			}
+			// this.updateComplete.then(
+			// 	(bool: boolean) =>
+			// 		item.scrollIntoView()
+			// )
+			// waiting for update complete is not enough
+			setTimeout(()=> item.scrollIntoView(),500)
+		} catch (e)
+		{
+			console.log("Could not scroll to item");
+		}
+	}
+
 	/**
 	 * Open an item, which might trigger lazy-loading
 	 *

api/js/etemplate/Et2Tree/Et2TreeDropdown.ts

@@ -118,6 +118,12 @@ export class Et2TreeDropdown extends SearchMixin<Constructor<any> & Et2InputWidg
 		return this._tree?.leafOnly;
 	}
 
+	/**
+	 * set the corresponding attribute if you want the tree to scroll to the selected item, when it is opened
+	 * Please already supply the parents of the current selection in an open state from the server side if possible
+	 */
+	@property({type: Boolean}) openAtSelection = false
+
 	@state() currentTag: Et2Tag;
 
 	// We show search results in the same dropdown
@@ -289,9 +295,14 @@ export class Et2TreeDropdown extends SearchMixin<Constructor<any> & Et2InputWidg
 			this.requestUpdate("open", true);
 			return this.updateComplete;
 		}
-
 		this.open = true;
 		this.requestUpdate("open", false)
+		if (this.openAtSelection)
+		{
+			//TODO check what to wait on, waiting on updateComplete does not work
+			setTimeout(() =>
+				this._tree.scrollToSelected(),100)
+		}
 		return this.updateComplete
 	}
 

preferences/inc/class.preferences_hooks.inc.php

@@ -381,6 +381,7 @@ class preferences_hooks
 				'attributes' => array(
 					'search' => true,
 					'leafOnly' => true, // don't allow to select continents
+                    'openAtSelection' => true, // scroll to selected item on open
 				)
 			),
 			'tz_selection' => array(