Enhance: Add spacing properties for DockPanel

components/Primitives/samples/DockPanelSample.xaml

@@ -1,4 +1,4 @@
-<!--  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.  -->
+<!--  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.  -->
 <Page x:Class="PrimitivesExperiment.Samples.DockPanelSample"
       xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
       xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
@@ -36,7 +36,9 @@
         <controls:DockPanel x:Name="SampleDockPanel"
                             Grid.Column="1"
                             Background="{ThemeResource CardBackgroundFillColorSecondaryBrush}"
-                            LastChildFill="False">
+                            HorizontalSpacing="5"
+                            LastChildFill="False"
+                            VerticalSpacing="5">
             <StackPanel Height="100"
                         controls:DockPanel.Dock="Top"
                         Background="Black" />

components/Primitives/src/DockPanel/DockPanel.Properties.cs

@@ -13,7 +13,7 @@ public partial class DockPanel
     /// Gets or sets a value that indicates the position of a child element within a parent <see cref="DockPanel"/>.
     /// </summary>
     public static readonly DependencyProperty DockProperty = DependencyProperty.RegisterAttached(
-        "Dock",
+        nameof(Dock),
         typeof(Dock),
         typeof(FrameworkElement),
         new PropertyMetadata(Dock.Left, DockChanged));
@@ -46,15 +46,15 @@ public static readonly DependencyProperty LastChildFillProperty
             nameof(LastChildFill),
             typeof(bool),
             typeof(DockPanel),
-            new PropertyMetadata(true, LastChildFillChanged));
+            new PropertyMetadata(true, OnPropertyChanged));
 
     /// <summary>
     /// Gets or sets a value indicating whether the last child element within a DockPanel stretches to fill the remaining available space.
     /// </summary>
     public bool LastChildFill
     {
-        get { return (bool)GetValue(LastChildFillProperty); }
-        set { SetValue(LastChildFillProperty, value); }
+        get => (bool)GetValue(LastChildFillProperty);
+        set => SetValue(LastChildFillProperty, value);
     }
 
     /// <summary>
@@ -66,7 +66,7 @@ public bool LastChildFill
             nameof(Padding),
             typeof(Thickness),
             typeof(DockPanel),
-            new PropertyMetadata(default(Thickness), OnPaddingChanged));
+            new PropertyMetadata(default(Thickness), OnPropertyChanged));
 
     /// <summary>
     /// Gets or sets the distance between the border and its child object.
@@ -77,7 +77,47 @@ public bool LastChildFill
     /// </returns>
     public Thickness Padding
     {
-        get { return (Thickness)GetValue(PaddingProperty); }
-        set { SetValue(PaddingProperty, value); }
+        get => (Thickness)GetValue(PaddingProperty); 
+        set => SetValue(PaddingProperty, value); 
+    }
+
+    /// <summary>
+    /// Identifies the HorizontalSpacing dependency property.
+    /// </summary>
+    /// <returns>The identifier for the <see cref="HorizontalSpacing"/> dependency property.</returns>
+    public static readonly DependencyProperty HorizontalSpacingProperty
+        = DependencyProperty.Register(
+            nameof(HorizontalSpacing), 
+            typeof(double), 
+            typeof(DockPanel), 
+            new PropertyMetadata(0d, OnPropertyChanged));
+
+    /// <summary>
+    /// Gets or sets the horizontal distance between the child objects.
+    /// </summary>
+    public double HorizontalSpacing
+    {
+        get => (double)GetValue(HorizontalSpacingProperty); 
+        set => SetValue(HorizontalSpacingProperty, value);
+    }
+
+    /// <summary>
+    /// Identifies the VerticalSpacing dependency property.
+    /// </summary>
+    /// <returns>The identifier for the <see cref="VerticalSpacing"/> dependency property.</returns>
+    public static readonly DependencyProperty VerticalSpacingProperty
+        = DependencyProperty.Register(
+            nameof(VerticalSpacing), 
+            typeof(double), 
+            typeof(DockPanel), 
+            new PropertyMetadata(default(double), OnPropertyChanged));
+
+    /// <summary>
+    /// Gets or sets the vertical distance between the child objects.
+    /// </summary>
+    public double VerticalSpacing
+    {
+        get => (double)GetValue(VerticalSpacingProperty); 
+        set => SetValue(VerticalSpacingProperty, value);
     }
 }

components/Primitives/src/DockPanel/DockPanel.cs

@@ -17,13 +17,7 @@ private static void DockChanged(DependencyObject sender, DependencyPropertyChang
         dockPanel?.InvalidateArrange();
     }
 
-    private static void LastChildFillChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
-    {
-        var dockPanel = (DockPanel)sender;
-        dockPanel.InvalidateArrange();
-    }
-
-    private static void OnPaddingChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
+    private static void OnPropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
     {
         var dockPanel = (DockPanel)sender;
         dockPanel.InvalidateMeasure();
@@ -32,15 +26,17 @@ private static void OnPaddingChanged(DependencyObject sender, DependencyProperty
     /// <inheritdoc />
     protected override Size ArrangeOverride(Size finalSize)
     {
-        if (Children.Count == 0)
-        {
+        if (Children.Count is 0)
             return finalSize;
-        }
 
-        var currentBounds = new Rect(Padding.Left, Padding.Top, finalSize.Width - Padding.Right, finalSize.Height - Padding.Bottom);
+        var currentBounds = new Rect(
+            Padding.Left,
+            Padding.Top,
+            GetPositiveOrZero(finalSize.Width - Padding.Left - Padding.Right),
+            GetPositiveOrZero(finalSize.Height - Padding.Top - Padding.Bottom));
         var childrenCount = LastChildFill ? Children.Count - 1 : Children.Count;
 
-        for (var index = 0; index < childrenCount; index++)
+        for (var index = 0; index < childrenCount; ++index)
         {
             var child = Children[index];
             var dock = (Dock)child.GetValue(DockProperty);
@@ -49,42 +45,45 @@ protected override Size ArrangeOverride(Size finalSize)
             {
                 case Dock.Left:
 
-                    width = Math.Min(child.DesiredSize.Width, GetPositiveOrZero(currentBounds.Width - currentBounds.X));
-                    child.Arrange(new Rect(currentBounds.X, currentBounds.Y, width, GetPositiveOrZero(currentBounds.Height - currentBounds.Y)));
+                    width = Math.Min(child.DesiredSize.Width, currentBounds.Width);
+                    child.Arrange(new Rect(currentBounds.X, currentBounds.Y, width, currentBounds.Height));
+                    width += HorizontalSpacing;
                     currentBounds.X += width;
+                    currentBounds.Width = GetPositiveOrZero(currentBounds.Width - width);
 
                     break;
                 case Dock.Top:
 
-                    height = Math.Min(child.DesiredSize.Height, GetPositiveOrZero(currentBounds.Height - currentBounds.Y));
-                    child.Arrange(new Rect(currentBounds.X, currentBounds.Y, GetPositiveOrZero(currentBounds.Width - currentBounds.X), height));
+                    height = Math.Min(child.DesiredSize.Height, currentBounds.Height);
+                    child.Arrange(new Rect(currentBounds.X, currentBounds.Y, currentBounds.Width, height));
+                    height += VerticalSpacing;
                     currentBounds.Y += height;
+                    currentBounds.Height = GetPositiveOrZero(currentBounds.Height - height);
 
                     break;
                 case Dock.Right:
 
-                    width = Math.Min(child.DesiredSize.Width, GetPositiveOrZero(currentBounds.Width - currentBounds.X));
-                    child.Arrange(new Rect(GetPositiveOrZero(currentBounds.Width - width), currentBounds.Y, width, GetPositiveOrZero(currentBounds.Height - currentBounds.Y)));
-                    currentBounds.Width -= (currentBounds.Width - width) > 0 ? width : 0;
+                    width = Math.Min(child.DesiredSize.Width, currentBounds.Width);
+                    child.Arrange(new Rect(currentBounds.X + currentBounds.Width - width, currentBounds.Y, width, currentBounds.Height));
+                    width += HorizontalSpacing;
+                    currentBounds.Width = GetPositiveOrZero(currentBounds.Width - width);
 
                     break;
                 case Dock.Bottom:
 
-                    height = Math.Min(child.DesiredSize.Height, GetPositiveOrZero(currentBounds.Height - currentBounds.Y));
-                    child.Arrange(new Rect(currentBounds.X, GetPositiveOrZero(currentBounds.Height - height), GetPositiveOrZero(currentBounds.Width - currentBounds.X), height));
-                    currentBounds.Height -= (currentBounds.Height - height) > 0 ? height : 0;
+                    height = Math.Min(child.DesiredSize.Height, currentBounds.Height);
+                    child.Arrange(new Rect(currentBounds.X, currentBounds.Y + currentBounds.Height - height, currentBounds.Width, height));
+                    height += VerticalSpacing;
+                    currentBounds.Height = GetPositiveOrZero(currentBounds.Height - height);
 
                     break;
             }
         }
 
         if (LastChildFill)
         {
-            var width = GetPositiveOrZero(currentBounds.Width - currentBounds.X);
-            var height = GetPositiveOrZero(currentBounds.Height - currentBounds.Y);
             var child = Children[Children.Count - 1];
-            child.Arrange(
-                new Rect(currentBounds.X, currentBounds.Y, width, height));
+            child.Arrange(new Rect(currentBounds.X, currentBounds.Y, currentBounds.Width, currentBounds.Height));
         }
 
         return finalSize;
@@ -98,6 +97,11 @@ protected override Size MeasureOverride(Size availableSize)
         var accumulatedWidth = Padding.Left + Padding.Right;
         var accumulatedHeight = Padding.Top + Padding.Bottom;
 
+        var leftSpacing = false;
+        var topSpacing = false;
+        var rightSpacing = false;
+        var bottomSpacing = false;
+
         foreach (var child in Children)
         {
             var childConstraint = new Size(
@@ -110,26 +114,48 @@ protected override Size MeasureOverride(Size availableSize)
             switch ((Dock)child.GetValue(DockProperty))
             {
                 case Dock.Left:
+                    if (childConstraint.Width is not 0)
+                        accumulatedWidth += HorizontalSpacing;
+                    leftSpacing = true;
+                    parentHeight = Math.Max(parentHeight, accumulatedHeight + childDesiredSize.Height - VerticalSpacing);
+                    accumulatedWidth += childDesiredSize.Width;
+                    break;
+
                 case Dock.Right:
-                    parentHeight = Math.Max(parentHeight, accumulatedHeight + childDesiredSize.Height);
+                    if (childConstraint.Width is not 0)
+                        accumulatedWidth += HorizontalSpacing;
+                    rightSpacing = true;
+                    parentHeight = Math.Max(parentHeight, accumulatedHeight + childDesiredSize.Height - VerticalSpacing);
                     accumulatedWidth += childDesiredSize.Width;
                     break;
 
                 case Dock.Top:
+                    if (childConstraint.Height is not 0)
+                        accumulatedHeight += VerticalSpacing;
+                    topSpacing = true;
+                    parentWidth = Math.Max(parentWidth, accumulatedWidth + childDesiredSize.Width - HorizontalSpacing);
+                    accumulatedHeight += childDesiredSize.Height;
+                    break;
+
                 case Dock.Bottom:
-                    parentWidth = Math.Max(parentWidth, accumulatedWidth + childDesiredSize.Width);
+                    if (childConstraint.Height is not 0)
+                        accumulatedHeight += VerticalSpacing;
+                    bottomSpacing = true;
+                    parentWidth = Math.Max(parentWidth, accumulatedWidth + childDesiredSize.Width - HorizontalSpacing);
                     accumulatedHeight += childDesiredSize.Height;
                     break;
             }
         }
 
+        if (leftSpacing || rightSpacing)
+            accumulatedWidth -= HorizontalSpacing;
+        if (bottomSpacing || topSpacing)
+            accumulatedHeight -= VerticalSpacing;
+
         parentWidth = Math.Max(parentWidth, accumulatedWidth);
         parentHeight = Math.Max(parentHeight, accumulatedHeight);
         return new Size(parentWidth, parentHeight);
     }
 
-    private static double GetPositiveOrZero(double value)
-    {
-        return Math.Max(value, 0);
-    }
+    private static double GetPositiveOrZero(double value) => Math.Max(value, 0);
 }