feat(calendar): Enable auto scrolling to today

Author: dr1rrb

src/Uno.UI/Microsoft/UI/Xaml/Controls/CalendarView/CalendarView_Partial.cs

@@ -1617,7 +1617,7 @@ private void ScrollToDate(
 			index = pHost.CalculateOffsetFromMinDate(date);
 			Debug.Assert(index >= 0);
 			Debug.Assert(pHost.Panel is {});
-			pHost.Panel.ScrollItemintoView(
+			pHost.Panel.ScrollItemIntoView(
 				index,
 				ScrollIntoViewAlignment.Leading,
 				0.0 /* offset */,

src/Uno.UI/Microsoft/UI/Xaml/Controls/CalendarView/Primitives/CalendarPanel.ModernCollectionBasePanel.cs

@@ -112,7 +112,7 @@ internal IEnumerable<CacheEntry> CompleteGeneration(int endIndex)
 				if (unexpectedUnusedEntries.count > 0)
 				{
 					// If actually all entries have been recycled, some entries might be part of the recyclable head.
-					unexpectedUnusedEntries.at = Math.Max(_generationRecyclableBefore.at, _generationRecyclableAfter.at - unexpectedUnusedEntries.count);
+					unexpectedUnusedEntries.at = Math.Max(_generationRecyclableBefore.at + _generationRecyclableBefore.count, _generationRecyclableAfter.at - unexpectedUnusedEntries.count);
 					unexpectedUnusedEntries.count = Math.Min(unexpectedUnusedEntries.count, _entries.Count - unexpectedUnusedEntries.at);
 				}
 
@@ -354,14 +354,19 @@ internal void DisconnectItemsHost()
 		internal DependencyObject? ContainerFromIndex(int index)
 			=> _cache.ContainerFromIndex(index);
 
-		[NotImplemented]
-		internal void ScrollItemintoView(int index, ScrollIntoViewAlignment alignment, double offset, bool forceSynchronous)
-		{
-		}
-
-		[NotImplemented]
 		internal void ScrollItemIntoView(int index, ScrollIntoViewAlignment alignment, double offset, bool forceSynchronous)
 		{
+			if (_layoutStrategy is null)
+			{
+				return;
+			}
+
+			_layoutStrategy.EstimateElementBounds(ElementType.ItemContainer, index, default, default, default, out var bounds);
+
+			Owner?.ScrollViewer?.ChangeView(
+				horizontalOffset: null,
+				verticalOffset: bounds.Y + offset,
+				zoomFactor: null);
 		}
 
 		private Size GetViewportSize()