Merge branch 'master' into wrapPanel.verticalAlignment

Author: vgromfeld

Microsoft.Toolkit.Uwp.UI.Controls/UniformGrid/TakenSpotsReferenceHolder.cs

@@ -2,11 +2,9 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+using System.Collections;
+using System.Drawing;
+using Microsoft.Toolkit.Diagnostics;
 
 namespace Microsoft.Toolkit.Uwp.UI.Controls
 {
@@ -16,23 +14,81 @@ namespace Microsoft.Toolkit.Uwp.UI.Controls
     /// <see cref="UniformGrid.GetFreeSpot"/> iterator.
     /// This is used so we can better isolate our logic and make it easier to test.
     /// </summary>
-    internal class TakenSpotsReferenceHolder
+    internal sealed class TakenSpotsReferenceHolder
     {
         /// <summary>
-        /// Gets or sets the array to hold taken spots.
-        /// True value indicates an item in the layout is fixed to that position.
-        /// False values indicate free openings where an item can be placed.
+        /// The <see cref="BitArray"/> instance used to efficiently track empty spots.
         /// </summary>
-        public bool[,] SpotsTaken { get; set; }
+        private readonly BitArray spotsTaken;
 
+        /// <summary>
+        /// Initializes a new instance of the <see cref="TakenSpotsReferenceHolder"/> class.
+        /// </summary>
+        /// <param name="rows">The number of rows to track.</param>
+        /// <param name="columns">The number of columns to track.</param>
         public TakenSpotsReferenceHolder(int rows, int columns)
         {
-            SpotsTaken = new bool[rows, columns];
+            Guard.IsGreaterThanOrEqualTo(rows, 0, nameof(rows));
+            Guard.IsGreaterThanOrEqualTo(columns, 0, nameof(columns));
+
+            Height = rows;
+            Width = columns;
+
+            this.spotsTaken = new BitArray(rows * columns);
+        }
+
+        /// <summary>
+        /// Gets the height of the grid to monitor.
+        /// </summary>
+        public int Height { get; }
+
+        /// <summary>
+        /// Gets the width of the grid to monitor.
+        /// </summary>
+        public int Width { get; }
+
+        /// <summary>
+        /// Gets or sets the value of a specified grid cell.
+        /// </summary>
+        /// <param name="i">The vertical offset.</param>
+        /// <param name="j">The horizontal offset.</param>
+        public bool this[int i, int j]
+        {
+            get => this.spotsTaken[(i * Width) + j];
+            set => this.spotsTaken[(i * Width) + j] = value;
+        }
+
+        /// <summary>
+        /// Fills the specified area in the current grid with a given value.
+        /// If invalid coordinates are given, they will simply be ignored and no exception will be thrown.
+        /// </summary>
+        /// <param name="value">The value to fill the target area with.</param>
+        /// <param name="row">The row to start on (inclusive, 0-based index).</param>
+        /// <param name="column">The column to start on (inclusive, 0-based index).</param>
+        /// <param name="width">The positive width of area to fill.</param>
+        /// <param name="height">The positive height of area to fill.</param>
+        public void Fill(bool value, int row, int column, int width, int height)
+        {
+            Rectangle bounds = new Rectangle(0, 0, Width, Height);
+
+            // Precompute bounds to skip branching in main loop
+            bounds.Intersect(new Rectangle(column, row, width, height));
+
+            for (int i = bounds.Top; i < bounds.Bottom; i++)
+            {
+                for (int j = bounds.Left; j < bounds.Right; j++)
+                {
+                    this[i, j] = value;
+                }
+            }
         }
 
-        public TakenSpotsReferenceHolder(bool[,] array)
+        /// <summary>
+        /// Resets the current reference holder.
+        /// </summary>
+        public void Reset()
         {
-            SpotsTaken = array;
+            this.spotsTaken.SetAll(false);
         }
     }
 }

Microsoft.Toolkit.Uwp.UI.Controls/UniformGrid/UniformGrid.Helpers.cs

@@ -22,16 +22,16 @@ public partial class UniformGrid : Grid
         {
             if (topdown)
             {
-                var rows = arrayref.SpotsTaken.GetLength(0);
+                var rows = arrayref.Height;
 
                 // Layout spots from Top-Bottom, Left-Right (right-left handled automatically by Grid with Flow-Direction).
                 // Effectively transpose the Grid Layout.
-                for (int c = 0; c < arrayref.SpotsTaken.GetLength(1); c++)
+                for (int c = 0; c < arrayref.Width; c++)
                 {
                     int start = (c == 0 && firstcolumn > 0 && firstcolumn < rows) ? firstcolumn : 0;
                     for (int r = start; r < rows; r++)
                     {
-                        if (!arrayref.SpotsTaken[r, c])
+                        if (!arrayref[r, c])
                         {
                             yield return (r, c);
                         }
@@ -40,17 +40,17 @@ public partial class UniformGrid : Grid
             }
             else
             {
-                var columns = arrayref.SpotsTaken.GetLength(1);
+                var columns = arrayref.Width;
 
                 // Layout spots as normal from Left-Right.
                 // (right-left handled automatically by Grid with Flow-Direction
                 // during its layout, internal model is always left-right).
-                for (int r = 0; r < arrayref.SpotsTaken.GetLength(0); r++)
+                for (int r = 0; r < arrayref.Height; r++)
                 {
                     int start = (r == 0 && firstcolumn > 0 && firstcolumn < columns) ? firstcolumn : 0;
                     for (int c = start; c < columns; c++)
                     {
-                        if (!arrayref.SpotsTaken[r, c])
+                        if (!arrayref[r, c])
                         {
                             yield return (r, c);
                         }

Microsoft.Toolkit.Uwp.UI.Controls/UniformGrid/UniformGrid.cs

@@ -5,7 +5,6 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using Microsoft.Toolkit.Extensions;
 using Windows.Foundation;
 using Windows.UI.Xaml;
 using Windows.UI.Xaml.Controls;
@@ -20,6 +19,11 @@ public partial class UniformGrid : Grid
         // Internal list we use to keep track of items that we don't have space to layout.
         private List<UIElement> _overflow = new List<UIElement>();
 
+        /// <summary>
+        /// The <see cref="TakenSpotsReferenceHolder"/> instance in use, if any.
+        /// </summary>
+        private TakenSpotsReferenceHolder _spotref;
+
         /// <inheritdoc/>
         protected override Size MeasureOverride(Size availableSize)
         {
@@ -36,7 +40,20 @@ protected override Size MeasureOverride(Size availableSize)
             SetupRowDefinitions(rows);
             SetupColumnDefinitions(columns);
 
-            var spotref = new TakenSpotsReferenceHolder(rows, columns);
+            TakenSpotsReferenceHolder spotref;
+
+            // If the last spot holder matches the size currently in use, just reset
+            // that instance and reuse it to avoid allocating a new bit array.
+            if (_spotref != null && _spotref.Height == rows && _spotref.Width == columns)
+            {
+                spotref = _spotref;
+
+                spotref.Reset();
+            }
+            else
+            {
+                spotref = _spotref = new TakenSpotsReferenceHolder(rows, columns);
+            }
 
             // Figure out which children we should automatically layout and where available openings are.
             foreach (var child in visible)
@@ -56,7 +73,8 @@ protected override Size MeasureOverride(Size availableSize)
                 else
                 {
                     SetAutoLayout(child, false);
-                    spotref.SpotsTaken.Fill(true, row, col, colspan, rowspan); // row, col, width, height
+
+                    spotref.Fill(true, row, col, colspan, rowspan);
                 }
             }
 
@@ -100,7 +118,7 @@ protected override Size MeasureOverride(Size availableSize)
                         if (rowspan > 1 || colspan > 1)
                         {
                             // TODO: Need to tie this into iterator
-                            spotref.SpotsTaken.Fill(true, row, column, GetColumnSpan(child), GetRowSpan(child)); // row, col, width, height
+                            spotref.Fill(true, row, column, colspan, rowspan);
                         }
                     }
                     else
@@ -135,7 +153,7 @@ protected override Size MeasureOverride(Size availableSize)
             }
 
             // Return our desired size based on the largest child we found, our dimensions, and spacing.
-            var desiredSize = new Size((maxWidth * (double)columns) + columnSpacingSize, (maxHeight * (double)rows) + rowSpacingSize);
+            var desiredSize = new Size((maxWidth * columns) + columnSpacingSize, (maxHeight * rows) + rowSpacingSize);
 
             // Required to perform regular grid measurement, but ignore result.
             base.MeasureOverride(desiredSize);