From a72e8e243d26cabab4fd5b859eb439205b76ee4d Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sat, 7 Feb 2015 19:09:46 +0100
Subject: [PATCH] Added ICommand and use it in Button.

---
 Perspex.Controls/Button.cs         | 53 ++++++++++++++++++++++++++++++
 Perspex.Input/ICommand.cs          | 19 +++++++++++
 Perspex.Input/Perspex.Input.csproj |  1 +
 3 files changed, 73 insertions(+)
 create mode 100644 Perspex.Input/ICommand.cs

diff --git a/Perspex.Controls/Button.cs b/Perspex.Controls/Button.cs
index 401aa7dc51..7422602c71 100644
--- a/Perspex.Controls/Button.cs
+++ b/Perspex.Controls/Button.cs
@@ -21,6 +21,12 @@ namespace Perspex.Controls
         public static readonly PerspexProperty<ClickMode> ClickModeProperty =
             PerspexProperty.Register<Button, ClickMode>("ClickMode");
 
+        public static readonly PerspexProperty<ICommand> CommandProperty =
+            PerspexProperty.Register<Button, ICommand>("Command");
+
+        public static readonly PerspexProperty<object> CommandParameterProperty =
+            PerspexProperty.Register<Button, object>("CommandParameter");
+
         public static readonly RoutedEvent<RoutedEventArgs> ClickEvent =
             RoutedEvent.Register<Button, RoutedEventArgs>("Click", RoutingStrategies.Bubble);
 
@@ -28,6 +34,7 @@ namespace Perspex.Controls
         {
             FocusableProperty.OverrideDefaultValue(typeof(Button), true);
             ClickEvent.AddClassHandler<Button>(x => x.OnClick);
+            CommandProperty.Changed.Subscribe(CommandChanged);
         }
 
         public event EventHandler<RoutedEventArgs> Click
@@ -42,6 +49,18 @@ namespace Perspex.Controls
             set { this.SetValue(ClickModeProperty, value); }
         }
 
+        public ICommand Command
+        {
+            get { return this.GetValue(CommandProperty); }
+            set { this.SetValue(CommandProperty, value); }
+        }
+
+        public object CommandParameter
+        {
+            get { return this.GetValue(CommandParameterProperty); }
+            set { this.SetValue(CommandParameterProperty, value); }
+        }
+
         protected override Size MeasureOverride(Size availableSize)
         {
             return base.MeasureOverride(availableSize);
@@ -54,6 +73,10 @@ namespace Perspex.Controls
 
         protected virtual void OnClick(RoutedEventArgs e)
         {
+            if (this.Command != null)
+            {
+                this.Command.Execute(this.CommandParameter);
+            }
         }
 
         protected override void OnPointerPressed(PointerPressEventArgs e)
@@ -84,6 +107,36 @@ namespace Perspex.Controls
             }
         }
 
+        private static void CommandChanged(PerspexPropertyChangedEventArgs e)
+        {
+            var button = e.Sender as Button;
+
+            if (button != null)
+            {
+                var oldCommand = e.OldValue as ICommand;
+                var newCommand = e.NewValue as ICommand;
+
+                if (oldCommand != null)
+                {
+                    oldCommand.CanExecuteChanged -= button.CanExecuteChanged;
+                }
+
+                if (newCommand != null)
+                {
+                    newCommand.CanExecuteChanged -= button.CanExecuteChanged;
+                }
+
+                button.CanExecuteChanged(button, EventArgs.Empty);
+            }
+        }
+
+        private void CanExecuteChanged(object sender, EventArgs e)
+        {
+            // HACK: Just set the IsEnabled property for the moment. This needs to be changed to 
+            // use IsEnabledCore etc. but it will do for now.
+            this.IsEnabled = this.Command == null || this.Command.CanExecute(this.CommandParameter);
+        }
+
         private void RaiseClickEvent()
         {
             RoutedEventArgs click = new RoutedEventArgs
diff --git a/Perspex.Input/ICommand.cs b/Perspex.Input/ICommand.cs
new file mode 100644
index 0000000000..0c7c08db04
--- /dev/null
+++ b/Perspex.Input/ICommand.cs
@@ -0,0 +1,19 @@
+// -----------------------------------------------------------------------
+// <copyright file="ICommand.cs" company="Steven Kirk">
+// Copyright 2015 MIT Licence. See licence.md for more information.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Perspex.Input
+{
+    using System;
+
+    public interface ICommand
+    {
+        event EventHandler CanExecuteChanged;
+
+        bool CanExecute(object parameter);
+
+        void Execute(object parameter);
+    }
+}
diff --git a/Perspex.Input/Perspex.Input.csproj b/Perspex.Input/Perspex.Input.csproj
index 239a4aeedf..f0f4d1cba1 100644
--- a/Perspex.Input/Perspex.Input.csproj
+++ b/Perspex.Input/Perspex.Input.csproj
@@ -60,6 +60,7 @@
     <Compile Include="FocusManager.cs" />
     <Compile Include="FocusNavigationDirection.cs" />
     <Compile Include="ICloseable.cs" />
+    <Compile Include="ICommand.cs" />
     <Compile Include="IFocusManager.cs" />
     <Compile Include="IFocusScope.cs" />
     <Compile Include="IInputDevice.cs" />