Allow better SegmentedButton theming

src/Eto.Wpf/Forms/Controls/ButtonHandler.cs

@@ -67,7 +67,6 @@ public int ImageLabelSpacing
 		protected override void Initialize()
 		{
 			Control.Click += (sender, e) => Callback.OnClick(Widget, EventArgs.Empty);
-			Control.Padding = new sw.Thickness(2);
 			LabelPart = new WpfLabel
 			{
 				IsHitTestVisible = false,

src/Eto.Wpf/Platform.cs

@@ -16,7 +16,6 @@
 using Eto.Shared.Forms;
 using System.Linq;
 using System.Diagnostics;
-
 namespace Eto.Wpf
 {
 	public class Platform : Eto.Platform
@@ -38,16 +37,28 @@ static Platform()
 
 			Style.Add<ThemedSegmentedButtonHandler>(null, h =>
 			{
-				h.Control.Styles.Add<ToggleButtonHandler>(null, tb =>
+				h.Widget.Items.CollectionChanged += (sender, e) =>
 				{
-					if (tb.Widget.Parent is TableLayout tl && tl.Rows.Count > 0 && tl.Spacing.Width == 0)
+					for (int i = 0; i < h.Widget.Items.Count; i++)
 					{
-						var isFirst = ReferenceEquals(tl.Rows[0].Cells[0].Control, tb.Widget);
-						var thickness = tb.Control.BorderThickness;
-						thickness.Left = isFirst ? thickness.Right : 0;
-						tb.Control.BorderThickness = thickness;
+						SegmentedItem item = h.Widget.Items[i];
+						if (item.ControlObject is Control control)
+						{
+							var native = control.ToNative();
+							if (native != null)
+							{
+								WpfProperties.SetEtoStyle(native, "SegmentedButton");
+								if (i == 0)
+									WpfProperties.SetEtoModifier(native, "first");
+								else if (i == h.Widget.Items.Count - 1)
+									WpfProperties.SetEtoModifier(native, "last");
+								else
+									native.ClearValue(WpfProperties.EtoModifierProperty);
+							}
+						}
+
 					}
-				});
+				};
 			});
 		}
 

src/Eto.Wpf/WpfProperties.cs

@@ -0,0 +1,25 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using sw = System.Windows;
+
+namespace Eto.Wpf
+{
+	public static class WpfProperties
+	{
+		public static string GetEtoStyle(sw.DependencyObject obj) => (string)obj.GetValue(EtoStyleProperty);
+		public static void SetEtoStyle(sw.DependencyObject obj, string value) => obj.SetValue(EtoStyleProperty, value);
+
+		public static readonly sw.DependencyProperty EtoStyleProperty =
+				sw.DependencyProperty.RegisterAttached("EtoStyle", typeof(string), typeof(WpfProperties), new sw.UIPropertyMetadata(string.Empty));
+
+
+
+		public static string GetEtoModifier(sw.DependencyObject obj) => (string)obj.GetValue(EtoModifierProperty);
+		public static void SetEtoModifier(sw.DependencyObject obj, string value) => obj.SetValue(EtoModifierProperty, value);
+
+		public static readonly sw.DependencyProperty EtoModifierProperty =
+				sw.DependencyProperty.RegisterAttached("EtoModifier", typeof(string), typeof(WpfProperties), new sw.UIPropertyMetadata(string.Empty));
+
+	}
+}

src/Eto.Wpf/themes/generic.xaml

@@ -2,6 +2,7 @@
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
     xmlns:r="clr-namespace:Eto.Wpf.CustomControls.TreeGridView"
     xmlns:efc="clr-namespace:Eto.Wpf.Forms.Controls"
+    xmlns:e="clr-namespace:Eto.Wpf"
     xmlns:s="clr-namespace:System;assembly=mscorlib">
 
     <ResourceDictionary.MergedDictionaries>
@@ -94,5 +95,55 @@
             </Setter>
         </Style.Setters>
     </Style>
+
+	<Style TargetType="efc:EtoButton">
+		<Setter Property="Padding" Value="2" />
+	</Style>
+
+    <Style TargetType="efc:EtoToggleButton">
+		<Setter Property="Padding" Value="2" />
+        <Style.Resources>
+            <Style TargetType="Border">
+                <Style.Triggers>
+                    <MultiDataTrigger>
+						<MultiDataTrigger.Conditions>
+							<Condition Binding="{Binding Path=(e:WpfProperties.EtoStyle), RelativeSource={RelativeSource AncestorType={x:Type efc:EtoToggleButton}}}" Value="SegmentedButton" />
+							<Condition Binding="{Binding Path=(e:WpfProperties.EtoModifier), RelativeSource={RelativeSource AncestorType={x:Type efc:EtoToggleButton}}}" Value="first" />
+						</MultiDataTrigger.Conditions>
+                        <Setter Property="CornerRadius" Value="4,0,0,4" />
+                    </MultiDataTrigger>
+                    <MultiDataTrigger>
+						<MultiDataTrigger.Conditions>
+							<Condition Binding="{Binding Path=(e:WpfProperties.EtoStyle), RelativeSource={RelativeSource AncestorType={x:Type efc:EtoToggleButton}}}" Value="SegmentedButton" />
+							<Condition Binding="{Binding Path=(e:WpfProperties.EtoModifier), RelativeSource={RelativeSource AncestorType={x:Type efc:EtoToggleButton}}}" Value="last" />
+						</MultiDataTrigger.Conditions>
+                        <Setter Property="CornerRadius" Value="0,4,4,0" />
+                    </MultiDataTrigger>
+                </Style.Triggers>
+            </Style>
+        </Style.Resources>
+        <Style.Triggers>
+            <Trigger Property="e:WpfProperties.EtoStyle" Value="SegmentedButton">
+                <Setter Property="BorderThickness" Value=".5,1" />
+                <Setter Property="Padding" Value="4,2" />
+            </Trigger>
+            <MultiTrigger>
+                <MultiTrigger.Conditions>
+                    <Condition Property="e:WpfProperties.EtoStyle" Value="SegmentedButton"/>
+                    <Condition Property="e:WpfProperties.EtoModifier" Value="first"/>
+                </MultiTrigger.Conditions>
+                <Setter Property="BorderThickness" Value="1,1,.5,1" />
+            </MultiTrigger>
+            <MultiTrigger>
+                <MultiTrigger.Conditions>
+                    <Condition Property="e:WpfProperties.EtoStyle" Value="SegmentedButton"/>
+                    <Condition Property="e:WpfProperties.EtoModifier" Value="last"/>
+                </MultiTrigger.Conditions>
+                <Setter Property="BorderThickness" Value=".5,1,1,1" />
+            </MultiTrigger>
+
+        </Style.Triggers>
+    </Style>
+
 
 </ResourceDictionary>

src/Eto/Forms/SegmentedButton/SegmentedButton.cs

@@ -61,6 +61,7 @@ static SegmentedButton()
 	public SegmentedButton()
 	{
 		Items = new SegmentedItemCollection(this);
+		Initialize();
 	}
 
 	/// <inheritdoc />
@@ -328,6 +329,7 @@ public void OnSelectedIndexesChanged(SegmentedButton widget, EventArgs e)
 	/// <summary>
 	/// Handler interface for <see cref="SegmentedButton"/>.
 	/// </summary>
+	[AutoInitialize(false)]
 	public new interface IHandler : Control.IHandler
 	{
 		/// <summary>

src/Eto/Forms/SegmentedButton/SegmentedItemCollection.cs

@@ -1,12 +1,13 @@
-using System.Collections.Generic;
+using System.Collections.Generic;
 using System.Collections.ObjectModel;
+using System.Collections.Specialized;
 
 namespace Eto.Forms;
 
 /// <summary>
 /// Collection of <see cref="SegmentedItem"/> objects for the <see cref="SegmentedButton"/>.
 /// </summary>
-public class SegmentedItemCollection : Collection<SegmentedItem>
+public class SegmentedItemCollection : ObservableCollection<SegmentedItem>
 {
 	SegmentedButton Parent { get; }
 	SegmentedButton.IHandler Handler => Parent.Handler as SegmentedButton.IHandler;
@@ -64,7 +65,8 @@ protected override void RemoveItem(int index)
 	/// <param name="item">Item to replace with.</param>
 	protected override void SetItem(int index, SegmentedItem item)
 	{
-		this[index].Parent = null;
+		var oldItem = this[index];
+		oldItem.Parent = null;
 		base.SetItem(index, item);
 		Handler.SetItem(index, item);
 		item.Parent = Parent;

src/Eto/Forms/ThemedControls/ThemedSegmentedButtonHandler.cs

@@ -19,13 +19,13 @@ public class ThemedMenuSegmentedItemHandler : ThemedSegmentedItemHandler<MenuSeg
 	/// <summary>
 	/// Delay for the menu to show when the mouse is down and <see cref="CanSelect"/> is <c>true</c>.
 	/// </summary>
-	public TimeSpan MenuDelay { get; set; } = TimeSpan.FromSeconds(0.5);
+	public virtual TimeSpan MenuDelay { get; set; } = TimeSpan.FromSeconds(0.5);
 
 	/// <summary>
 	/// Gets or sets the indicator to show to the right of the text.
 	/// </summary>
 	/// <value>The menu indicator.</value>
-	public string MenuIndicator
+	public virtual string MenuIndicator
 	{
 		get => menuIndicator;
 		set
@@ -36,10 +36,10 @@ public string MenuIndicator
 	}
 
 	/// <inheritdoc/>
-	public ContextMenu Menu { get; set; }
+	public virtual ContextMenu Menu { get; set; }
 
 	/// <inheritdoc/>
-	public bool CanSelect { get; set; }
+	public virtual bool CanSelect { get; set; }
 
 	/// <inheritdoc/>
 	public override string Text
@@ -125,13 +125,13 @@ public abstract class ThemedSegmentedItemHandler<TWidget, TCallback> : WidgetHan
 	protected ThemedSegmentedButtonHandler ParentHandler => Widget.Parent?.Handler as ThemedSegmentedButtonHandler;
 
 	/// <inheritdoc/>
-	public bool Enabled { get => Control.Enabled; set => Control.Enabled = value; }
+	public virtual bool Enabled { get => Control.Enabled; set => Control.Enabled = value; }
 	/// <inheritdoc/>
-	public bool Visible { get => Control.Visible; set => Control.Visible = value; }
+	public virtual bool Visible { get => Control.Visible; set => Control.Visible = value; }
 	/// <inheritdoc/>
-	public string ToolTip { get => Control.ToolTip; set => Control.ToolTip = value; }
+	public virtual string ToolTip { get => Control.ToolTip; set => Control.ToolTip = value; }
 	/// <inheritdoc/>
-	public int Width { get => Control.Width; set => Control.Width = value; }
+	public virtual int Width { get => Control.Width; set => Control.Width = value; }
 	/// <inheritdoc/>
 	public virtual string Text
 	{
@@ -143,9 +143,9 @@ public virtual string Text
 		}
 	}
 	/// <inheritdoc/>
-	public Image Image { get => Control.Image; set => Control.Image = value; }
+	public virtual Image Image { get => Control.Image; set => Control.Image = value; }
 	/// <inheritdoc/>
-	public bool Selected
+	public virtual bool Selected
 	{
 		get => Control.Checked;
 		set
@@ -224,7 +224,7 @@ public class ThemedSegmentedButtonHandler : ThemedControlHandler<Panel, Segmente
 	protected override Panel CreateControl() => new Panel();
 
 	/// <inheritdoc/>
-	public SegmentedSelectionMode SelectionMode
+	public virtual SegmentedSelectionMode SelectionMode
 	{
 		get => selectionMode;
 		set
@@ -247,10 +247,10 @@ public SegmentedSelectionMode SelectionMode
 	/// Gets or sets the spacing between the buttons
 	/// </summary>
 	/// <value>The spacing between the buttons.</value>
-	public int Spacing { get; set; }
+	public virtual int Spacing { get; set; }
 
 	/// <inheritdoc/>
-	public int SelectedIndex
+	public virtual int SelectedIndex
 	{
 		get
 		{
@@ -273,7 +273,7 @@ public int SelectedIndex
 	}
 
 	/// <inheritdoc/>
-	public IEnumerable<int> SelectedIndexes
+	public virtual IEnumerable<int> SelectedIndexes
 	{
 		get
 		{
@@ -309,7 +309,7 @@ public IEnumerable<int> SelectedIndexes
 	}
 
 	/// <inheritdoc/>
-	public void ClearItems()
+	public virtual void ClearItems()
 	{
 		var hasSelected = SelectedIndex != -1;
 		CreateTable(false);
@@ -322,7 +322,7 @@ public void ClearItems()
 	TableCell GetCell(SegmentedItem item) => new TableCell(GetControl(item));
 
 	/// <inheritdoc/>
-	public void ClearSelection()
+	public virtual void ClearSelection()
 	{
 		suppressSelectionChanged++;
 		var wasSelected = false;
@@ -338,7 +338,7 @@ public void ClearSelection()
 	}
 
 	/// <inheritdoc/>
-	public void InsertItem(int index, SegmentedItem item)
+	public virtual void InsertItem(int index, SegmentedItem item)
 	{
 		var isSelected = item.Selected;
 		CreateTable(false);
@@ -354,7 +354,7 @@ public void InsertItem(int index, SegmentedItem item)
 	}
 
 	/// <inheritdoc/>
-	public void RemoveItem(int index, SegmentedItem item)
+	public virtual void RemoveItem(int index, SegmentedItem item)
 	{
 		var wasSelected = item.Selected;
 		CreateTable(false);
@@ -363,7 +363,7 @@ public void RemoveItem(int index, SegmentedItem item)
 	}
 
 	/// <inheritdoc/>
-	public void SelectAll()
+	public virtual void SelectAll()
 	{
 		suppressSelectionChanged++;
 		bool wasChanged = false;
@@ -378,7 +378,7 @@ public void SelectAll()
 	}
 
 	/// <inheritdoc/>
-	public void SetItem(int index, SegmentedItem item)
+	public virtual void SetItem(int index, SegmentedItem item)
 	{
 		var wasSelected = Widget.Items[index].Selected;
 		var isSelected = item.Selected;