Added IScrollable interface.

This is now the basic Extent/Offset/Viewport interface. Implemented by
ScrollViewer and ScrollContentPresenter.

samples/XamlTestApplicationPcl/TestScrollable.cs

@@ -18,12 +18,12 @@ namespace XamlTestApplication
         public bool IsLogicalScrollEnabled => true;
         public Action InvalidateScroll { get; set; }
 
-        Size ILogicalScrollable.Extent
+        Size IScrollable.Extent
         {
             get { return _extent; }
         }
 
-        Vector ILogicalScrollable.Offset
+        Vector IScrollable.Offset
         {
             get { return _offset; }
 
@@ -34,7 +34,7 @@ namespace XamlTestApplication
             }
         }
 
-        Size ILogicalScrollable.Viewport
+        Size IScrollable.Viewport
         {
             get { return _viewport; }
         }

src/Avalonia.Controls/Avalonia.Controls.csproj

@@ -54,6 +54,7 @@
     <Compile Include="Generators\TreeContainerIndex.cs" />
     <Compile Include="HotkeyManager.cs" />
     <Compile Include="IApplicationLifecycle.cs" />
+    <Compile Include="IScrollable.cs" />
     <Compile Include="INameScope.cs" />
     <Compile Include="IPseudoClasses.cs" />
     <Compile Include="DropDownItem.cs" />

src/Avalonia.Controls/IScrollable.cs

@@ -0,0 +1,29 @@
+// Copyright (c) The Avalonia Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using System;
+using Avalonia.VisualTree;
+
+namespace Avalonia.Controls.Primitives
+{
+    /// <summary>
+    /// Interface implemented by scrollable controls.
+    /// </summary>
+    public interface IScrollable
+    {
+        /// <summary>
+        /// Gets the extent of the scrollable content, in logical units
+        /// </summary>
+        Size Extent { get; }
+
+        /// <summary>
+        /// Gets or sets the current scroll offset, in logical units.
+        /// </summary>
+        Vector Offset { get; set; }
+
+        /// <summary>
+        /// Gets the size of the viewport, in logical units.
+        /// </summary>
+        Size Viewport { get; }
+    }
+}

src/Avalonia.Controls/Presenters/ItemsPresenter.cs

@@ -51,20 +51,20 @@ namespace Avalonia.Controls.Presenters
         }
 
         /// <inheritdoc/>
-        Action ILogicalScrollable.InvalidateScroll { get; set; }
-
-        /// <inheritdoc/>
-        Size ILogicalScrollable.Extent => _virtualizer.Extent;
+        Size IScrollable.Extent => _virtualizer.Extent;
 
         /// <inheritdoc/>
-        Vector ILogicalScrollable.Offset
+        Vector IScrollable.Offset
         {
             get { return _virtualizer.Offset; }
             set { _virtualizer.Offset = CoerceOffset(value); }
         }
 
         /// <inheritdoc/>
-        Size ILogicalScrollable.Viewport => _virtualizer.Viewport;
+        Size IScrollable.Viewport => _virtualizer.Viewport;
+
+        /// <inheritdoc/>
+        Action ILogicalScrollable.InvalidateScroll { get; set; }
 
         /// <inheritdoc/>
         Size ILogicalScrollable.ScrollSize => new Size(0, 1);

src/Avalonia.Controls/Presenters/ScrollContentPresenter.cs

@@ -15,7 +15,7 @@ namespace Avalonia.Controls.Presenters
     /// <summary>
     /// Presents a scrolling view of content inside a <see cref="ScrollViewer"/>.
     /// </summary>
-    public class ScrollContentPresenter : ContentPresenter, IPresenter
+    public class ScrollContentPresenter : ContentPresenter, IPresenter, IScrollable
     {
         /// <summary>
         /// Defines the <see cref="Extent"/> property.

src/Avalonia.Controls/Primitives/ILogicalScrollable.cs

@@ -17,7 +17,7 @@ namespace Avalonia.Controls.Primitives
     /// whereas logical scrolling means that the scrolling is handled by the child control itself
     /// and it can choose to do handle the scroll information as it sees fit.
     /// </remarks>
-    public interface ILogicalScrollable
+    public interface ILogicalScrollable : IScrollable
     {
         /// <summary>
         /// Gets a value indicating whether logical scrolling is enabled on the control.
@@ -30,7 +30,8 @@ namespace Avalonia.Controls.Primitives
         /// <remarks>
         /// <para>
         /// This method notifies the attached <see cref="ScrollViewer"/> of a change in 
-        /// the <see cref="Extent"/>, <see cref="Offset"/> or <see cref="Viewport"/> properties.
+        /// the <see cref="IScrollable.Extent"/>, <see cref="IScrollable.Offset"/> or 
+        /// <see cref="IScrollable.Viewport"/> properties.
         /// </para>
         /// <para>
         /// This property is set by the parent <see cref="ScrollViewer"/> when the 
@@ -39,21 +40,6 @@ namespace Avalonia.Controls.Primitives
         /// </remarks>
         Action InvalidateScroll { get; set; }
 
-        /// <summary>
-        /// Gets the extent of the scrollable content, in logical units
-        /// </summary>
-        Size Extent { get; }
-
-        /// <summary>
-        /// Gets or sets the current scroll offset, in logical units.
-        /// </summary>
-        Vector Offset { get; set; }
-
-        /// <summary>
-        /// Gets the size of the viewport, in logical units.
-        /// </summary>
-        Size Viewport { get; }
-
         /// <summary>
         /// Gets the size to scroll by, in logical units.
         /// </summary>

src/Avalonia.Controls/ScrollViewer.cs

@@ -12,7 +12,7 @@ namespace Avalonia.Controls
     /// <summary>
     /// A control scrolls its content if the content is bigger than the space available.
     /// </summary>
-    public class ScrollViewer : ContentControl
+    public class ScrollViewer : ContentControl, IScrollable
     {
         /// <summary>
         /// Defines the <see cref="CanScrollHorizontally"/> property.