Added some basic logic to a custom layouting class

Author: 0x5bfa

src/Files.App.Controls/BreadcrumbBar/BreadcrumbBar.Events.cs

@@ -80,5 +80,13 @@ private void RootItemChevronDropDownMenuFlyout_Closed(object? sender, object e)
 			VisualStateManager.GoToState(this, "ChevronNormalOff", true);
 			VisualStateManager.GoToState(this, "PointerNormal", true);
 		}
+
+		private void ItemsRepeater_ElementPrepared(ItemsRepeater sender, ItemsRepeaterElementPreparedEventArgs args)
+		{
+			if (args.Element is not BreadcrumbBarItem item)
+				return;
+
+			item.SetOwner(this);
+		}
 	}
 }

src/Files.App.Controls/BreadcrumbBar/BreadcrumbBar.cs

@@ -105,15 +105,5 @@ internal void RaiseItemDropDownFlyoutClosed(BreadcrumbBarItem item, MenuFlyout f
 			var index = _itemsRepeater?.GetElementIndex(item) ?? throw new ArgumentNullException($"{_itemsRepeater} is null.");
 			ItemDropDownFlyoutClosed?.Invoke(this, new(flyout, item, index));
 		}
-
-		// Event methods
-
-		private void ItemsRepeater_ElementPrepared(ItemsRepeater sender, ItemsRepeaterElementPreparedEventArgs args)
-		{
-			if (args.Element is not BreadcrumbBarItem item)
-				return;
-
-			item.SetOwner(this);
-		}
 	}
 }

src/Files.App.Controls/BreadcrumbBar/BreadcrumbBarLayout.cs

@@ -8,16 +8,66 @@
 using Microsoft.UI.Xaml.Markup;
 using Microsoft.UI.Xaml.Media;
 using Microsoft.UI.Xaml.Shapes;
+using Windows.Foundation;
 
 namespace Files.App.Controls
 {
 	public partial class BreadcrumbBarLayout : NonVirtualizingLayout
 	{
+		private Size _availableSize;
+		private BreadcrumbBarItem? _ellipsisButton = null;
 		private WeakReference<BreadcrumbBar>? _ownerRef;
 
+		private bool _ellipsisIsRendered;
+		private uint _firstRenderedItemIndexAfterEllipsis;
+		private uint _visibleItemsCount;
+
 		public BreadcrumbBarLayout(BreadcrumbBar breadcrumb)
 		{
 			_ownerRef = new(breadcrumb);
 		}
+
+		protected override Size MeasureOverride(NonVirtualizingLayoutContext context, Size availableSize)
+		{
+			var accumulatedSize = new Size(0, 0);
+
+			// Go through all items and measure them
+			foreach (var item in context.Children)
+			{
+				if (item is BreadcrumbBarItem breadcrumbItem)
+				{
+					breadcrumbItem.Measure(availableSize);
+					accumulatedSize.Width += breadcrumbItem.DesiredSize.Width;
+					accumulatedSize.Height = Math.Max(accumulatedSize.Height, breadcrumbItem.DesiredSize.Height);
+				}
+			}
+
+			// Get a reference to the ellipsis item
+			if (context.Children.Count is not 0)
+				_ellipsisButton ??= context.Children[0] as BreadcrumbBarItem;
+
+			// Sets the ellipsis item's visibility based on whether the items are overflowing
+			_ellipsisIsRendered = accumulatedSize.Width > availableSize.Width;
+
+			return accumulatedSize;
+		}
+
+		protected override Size ArrangeOverride(NonVirtualizingLayoutContext context, Size finalSize)
+		{
+			float accumulatedWidths = 0f;
+
+			// Go through all items and arrange them
+			foreach (var item in context.Children)
+			{
+				if (item is BreadcrumbBarItem breadcrumbItem)
+				{
+					breadcrumbItem.Arrange(new Rect(accumulatedWidths, 0, breadcrumbItem.DesiredSize.Width, finalSize.Height));
+
+					accumulatedWidths += (float)breadcrumbItem.Width;
+				}
+			}
+
+			return finalSize;
+		}
 	}
 }