Added OverflowBehaviors for StretchPanel

Author: Avid29

components/StretchPanel/samples/StretchPanelBasicSample.xaml

@@ -27,7 +27,8 @@
                                HorizontalAlignment="{x:Bind LayoutHorizontalAlignment, Mode=OneWay}"
                                VerticalAlignment="{x:Bind LayoutVerticalAlignment, Mode=OneWay}"
                                FixedRowLengths="{x:Bind FixedRowLengths, Mode=OneWay}"
-                               ForcedStretchMethod="{x:Bind local:StretchPanelBasicSample.ConvertStringToForcedStretchMethod(LayoutForcedStretchMethod), Mode=OneWay}">
+                               ForcedStretchMethod="{x:Bind local:StretchPanelBasicSample.ConvertStringToForcedStretchMethod(LayoutForcedStretchMethod), Mode=OneWay}"
+                               OverflowBehavior="{x:Bind local:StretchPanelBasicSample.ConvertStringToOverflowBehavior(LayoutOverflowBehavior), Mode=OneWay}">
             <Border controls:StretchPanel.LayoutLength="2*" >
                 <TextBlock Text="2*" HorizontalAlignment="Center"/>
             </Border>

components/StretchPanel/samples/StretchPanelBasicSample.xaml.cs

@@ -16,6 +16,7 @@ namespace StretchPanelExperiment.Samples;
 [ToolkitSampleNumericOption("VerticalSpacing", 2, 0, 16, Title = "Vertical Spacing")]
 [ToolkitSampleBoolOption("FixedRowLengths", false, Title = "Fixed Row Lengths")]
 [ToolkitSampleMultiChoiceOption("LayoutForcedStretchMethod", "None", "First", "Last", "Equal", "Proportional", Title = "Forced Stretch Method")]
+[ToolkitSampleMultiChoiceOption("LayoutOverflowBehavior", "Wrap", "Drop", Title = "Overflow Behavior")]
 
 [ToolkitSample(id: nameof(StretchPanelBasicSample), "Custom control", description: $"A sample for showing how to create and use a {nameof(StretchPanel)} custom control.")]
 public sealed partial class StretchPanelBasicSample : Page
@@ -63,4 +64,12 @@ public StretchPanelBasicSample()
         "Proportional" => ForcedStretchMethod.Proportional,
         _ => throw new System.NotImplementedException(),
     };
+
+    // TODO: See https://github.com/CommunityToolkit/Labs-Windows/issues/149
+    public static OverflowBehavior ConvertStringToOverflowBehavior(string overflowBehavior) => overflowBehavior switch
+    {
+        "Wrap" => OverflowBehavior.Wrap,
+        "Drop" => OverflowBehavior.Drop,
+        _ => throw new System.NotImplementedException(),
+    };
 }

components/StretchPanel/src/OverflowBehavior.cs

@@ -0,0 +1,21 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace CommunityToolkit.WinUI.Controls;
+
+/// <summary>
+/// Describes the behavior of items that exceed the available space in the panel.
+/// </summary>
+public enum OverflowBehavior
+{
+    /// <summary>
+    /// When an item exceeds the available space, it will be moved to a new row or column.
+    /// </summary>
+    Wrap,
+
+    /// <summary>
+    /// Items which do not fit within the available space will be removed from the layout.
+    /// </summary>
+    Drop,
+}

components/StretchPanel/src/StretchPanel.Properties.cs

@@ -59,7 +59,16 @@ public partial class StretchPanel
         nameof(ForcedStretchMethod),
         typeof(ForcedStretchMethod),
         typeof(StretchPanel),
-        new PropertyMetadata(default(bool), OnPropertyChanged));
+        new PropertyMetadata(default(ForcedStretchMethod), OnPropertyChanged));
+
+    /// <summary>
+    /// Backing <see cref="DependencyProperty"/> for the <see cref="OverflowBehavior"/> property.
+    /// </summary>
+    public static readonly DependencyProperty OverflowBehaviorProperty = DependencyProperty.Register(
+        nameof(OverflowBehavior),
+        typeof(OverflowBehavior),
+        typeof(StretchPanel),
+        new PropertyMetadata(default(OverflowBehavior), OnPropertyChanged));
 
     /// <summary>
     /// Gets or sets the panel orientation.
@@ -106,6 +115,15 @@ public ForcedStretchMethod ForcedStretchMethod
         set => SetValue(ForcedStretchMethodProperty, value);
     }
 
+    /// <summary>
+    /// Gets or sets how the panel handles content overflowing the available space.
+    /// </summary>
+    public OverflowBehavior OverflowBehavior
+    {
+        get => (OverflowBehavior)GetValue(OverflowBehaviorProperty);
+        set => SetValue(OverflowBehaviorProperty, value);
+    }
+
     /// <summary>
     /// Gets the <see cref="LayoutLengthProperty"/> of an item in the <see cref="StretchPanel"/>.
     /// </summary>

components/StretchPanel/src/StretchPanel.cs

@@ -43,6 +43,10 @@ protected override Size MeasureOverride(Size availableSize)
             var spec = new RowSpec(layoutLength, uvDesiredSize);
             if (!currentRowSpec.TryAdd(spec, uvSpacing.U, uvAvailableSize.U))
             {
+                // If the overflow behavior is drop, just end the row here.
+                if (OverflowBehavior is OverflowBehavior.Drop)
+                    break;
+
                 // Could not add to current row/column
                 // Start a new row/column
                 _rowSpecs.Add(currentRowSpec);
@@ -62,6 +66,9 @@ protected override Size MeasureOverride(Size availableSize)
             V = _rowSpecs.Sum(static rs => rs.MaxOffAxisSize) + (uvSpacing.V * (_rowSpecs.Count - 1))
         };
 
+        // Clamp to available size and return
+        uvSize.U = Math.Min(uvSize.U, uvAvailableSize.U);
+        uvSize.V = Math.Min(uvSize.V, uvAvailableSize.V);
         return uvSize.Size;
     }
 
@@ -89,6 +96,13 @@ protected override Size ArrangeOverride(Size finalSize)
             ArrangeRow(ref pos, row, uvFinalSize, uvSpacing, childQueue);
         }
 
+        // "Arrange" remaning children by rendering them with zero size
+        while (childQueue.TryDequeue(out var child))
+        {
+            // Arrange with zero size
+            child.Arrange(new Rect(0, 0, 0, 0));
+        }
+
         return finalSize;
     }