improved macios rendering performance

MPowerKit.VirtualizeListView/CellHolder.cs

@@ -7,8 +7,6 @@ public class CellHolder : Grid
 
     public CellHolder()
     {
-        VerticalOptions = HorizontalOptions = LayoutOptions.Start;
-
         this.SizeChanged += CellHolder_SizeChanged;
     }
 

MPowerKit.VirtualizeListView/Layouts/LinearItemsLayoutManager.cs

@@ -46,9 +46,24 @@ protected override Size MeasureItem(IReadOnlyList<VirtualizeListViewItem> items,
 
         var iview = (item.Cell as IView)!;
 
-        return IsOrientation(ScrollOrientation.Vertical)
-            ? iview.Measure(availableSpace.Width, double.PositiveInfinity)
-            : iview.Measure(double.PositiveInfinity, availableSpace.Height);
+        Size measure;
+
+        if (IsOrientation(ScrollOrientation.Vertical))
+        {
+            measure = iview.Measure(availableSpace.Width, double.PositiveInfinity);
+
+            item.CellBounds = new Rect(item.CellBounds.X, item.CellBounds.Y, availableSpace.Width, measure.Height);
+            item.Bounds = new Rect(item.Bounds.X, item.Bounds.Y, availableSpace.Width, measure.Height + item.Margin.VerticalThickness);
+        }
+        else
+        {
+            measure = iview.Measure(double.PositiveInfinity, availableSpace.Height);
+
+            item.CellBounds = new Rect(item.CellBounds.X, item.CellBounds.Y, measure.Width, availableSpace.Height);
+            item.Bounds = new Rect(item.Bounds.X, item.Bounds.Y, measure.Width + item.Margin.HorizontalThickness, availableSpace.Height);
+        }
+
+        return measure;
     }
 
     protected override void ArrangeItem(IReadOnlyList<VirtualizeListViewItem> items, VirtualizeListViewItem item, Size availableSpace)
@@ -71,21 +86,21 @@ protected override void ArrangeItem(IReadOnlyList<VirtualizeListViewItem> items,
 
             var newAvailableSpace = new Size(availableSpace.Width, availableSpace.Height);
 
-            var request = MeasureItem(items, item, newAvailableSpace);
+            item.CellBounds = new Rect(margin.Left, top + margin.Top, 0d, 0d);
+            item.Bounds = new Rect(0d, top, 0d, 0d);
 
-            item.CellBounds = new Rect(margin.Left, top + margin.Top, newAvailableSpace.Width, request.Height);
-            item.Bounds = new Rect(0d, top, newAvailableSpace.Width, request.Height + margin.VerticalThickness);
+            MeasureItem(items, item, newAvailableSpace);
         }
         else
         {
             var left = prevItemBounds.Right;
 
             var newAvailableSpace = new Size(availableSpace.Width, availableSpace.Height);
 
-            var request = MeasureItem(items, item, newAvailableSpace);
+            item.CellBounds = new Rect(left + margin.Left, margin.Top, 0d, 0d);
+            item.Bounds = new Rect(left, 0d, 0d, 0d);
 
-            item.CellBounds = new Rect(left + margin.Left, margin.Top, request.Width, newAvailableSpace.Height);
-            item.Bounds = new Rect(left, 0d, request.Width + margin.HorizontalThickness, newAvailableSpace.Height);
+            MeasureItem(items, item, newAvailableSpace);
         }
     }
 

MPowerKit.VirtualizeListView/Layouts/VirtualizeItemsLayoutManger.cs

@@ -701,6 +701,21 @@ protected virtual bool DrawAndTriggerResize()
         return TriggerResizeLayout();
     }
 
+    protected virtual void DrawItem(IReadOnlyList<VirtualizeListViewItem> items, VirtualizeListViewItem item)
+    {
+        if (items.Count == 0 || item.Position < 0 || item.Cell is null) return;
+
+        var view = item.Cell;
+#if !ANDROID
+        if (view.TranslationX != view.Item.CellBounds.X ||
+            view.TranslationY != view.Item.CellBounds.Y)
+        {
+            view.TranslationX = view.Item.CellBounds.X;
+            view.TranslationY = view.Item.CellBounds.Y;
+        }
+#endif
+    }
+
     protected virtual bool TriggerResizeLayout()
     {
         Size desiredSize = new();
@@ -747,34 +762,12 @@ protected virtual VirtualizeListViewItem CreateDummyItem(DataTemplate template,
             Position = 0
         };
 
-        var size =
-#if MACIOS
-            //macios needs this to properly draw pooled cached cell
-            (cell as IView).Measure(double.PositiveInfinity, double.PositiveInfinity);
-#else
-            GetEstimatedItemSize(item);
-#endif
-
+        var size = GetEstimatedItemSize(item);
         item.CellBounds = item.Bounds = new(0d, 0d, size.Width, size.Height);
 
         return item;
     }
 
-    protected virtual void DrawItem(IReadOnlyList<VirtualizeListViewItem> items, VirtualizeListViewItem item)
-    {
-        if (items.Count == 0 || item.Position < 0 || item.Cell is null) return;
-
-        var view = item.Cell;
-#if !ANDROID
-        if (view.TranslationX != view.Item.CellBounds.X ||
-            view.TranslationY != view.Item.CellBounds.Y)
-        {
-            view.TranslationX = view.Item.CellBounds.X;
-            view.TranslationY = view.Item.CellBounds.Y;
-        }
-#endif
-    }
-
     protected virtual Thickness GetItemMargin(IReadOnlyList<VirtualizeListViewItem> items, VirtualizeListViewItem item)
     {
         return new Thickness();
@@ -798,8 +791,6 @@ protected virtual bool IsOrientation(ScrollOrientation orientation)
     #region ILayoutManager
     public virtual Size Measure(double widthConstraint, double heightConstraint)
     {
-        var desiredSize = GetDesiredLayoutSize(widthConstraint, heightConstraint);
-
         var items = CollectionsMarshal.AsSpan((this as IBindableLayout).Children as List<IView>);
         var length = items.Length;
 
@@ -813,9 +804,11 @@ public virtual Size Measure(double widthConstraint, double heightConstraint)
             if (view.IsCached || !view.Item.IsAttached) continue;
 
             // this triggers item size change when needed
-            var measure = MeasureItem(LaidOutItems, view.Item, availableSpace);
+            MeasureItem(LaidOutItems, view.Item, availableSpace);
         }
 
+        var desiredSize = GetDesiredLayoutSize(widthConstraint, heightConstraint);
+
         return desiredSize;
     }
 
@@ -834,18 +827,15 @@ public virtual Size ArrangeChildren(Rect bounds)
             var child = items[n];
             var view = child as CellHolder;
 
-#if !MACIOS
             if (view.IsCached || !view.Item.IsAttached) continue;
-#endif
 
             var (x, y) =
 #if ANDROID
                 (view.Item.CellBounds.X, view.Item.CellBounds.Y);
 #else
                 (0d, 0d);
 #endif
-
-            var newBounds = new Rect(x, y, view.DesiredSize.Width, view.DesiredSize.Height);
+            var newBounds = new Rect(x, y, view.Item.CellBounds.Width, view.Item.CellBounds.Height);
 
 #if MACIOS
             if (view.Bounds == newBounds) continue;