[C] unify Padding into IPaddingElement (#1276)

Xamarin.Forms.Core/Frame.cs

@@ -5,7 +5,7 @@ namespace Xamarin.Forms
 {
 	[ContentProperty("Content")]
 	[RenderWith(typeof(_FrameRenderer))]
-	public class Frame : ContentView, IElementConfiguration<Frame>
+	public class Frame : ContentView, IElementConfiguration<Frame>, IPaddingElement
 	{
 		public static readonly BindableProperty OutlineColorProperty = BindableProperty.Create("OutlineColor", typeof(Color), typeof(Frame), Color.Default);
 
@@ -21,7 +21,7 @@ namespace Xamarin.Forms
 			_platformConfigurationRegistry = new Lazy<PlatformConfigurationRegistry<Frame>>(() => new PlatformConfigurationRegistry<Frame>(this));
 		}
 
-		internal override Thickness CreateDefaultPadding()
+		Thickness IPaddingElement.PaddingDefaultValueCreator()
 		{
 			return 20d;
 		}

Xamarin.Forms.Core/IPaddingElement.cs

@@ -0,0 +1,12 @@
+namespace Xamarin.Forms
+{
+	interface IPaddingElement
+	{
+		//note to implementor: implement this property publicly
+		Thickness Padding { get; }
+
+		//note to implementor: but implement this method explicitly
+		void OnPaddingPropertyChanged(Thickness oldValue, Thickness newValue);
+		Thickness PaddingDefaultValueCreator();
+	}
+}

Xamarin.Forms.Core/Layout.cs

@@ -50,16 +50,11 @@ namespace Xamarin.Forms
 		}
 	}
 
-	public abstract class Layout : View, ILayout, ILayoutController
+	public abstract class Layout : View, ILayout, ILayoutController, IPaddingElement
 	{
 		public static readonly BindableProperty IsClippedToBoundsProperty = BindableProperty.Create("IsClippedToBounds", typeof(bool), typeof(Layout), false);
 
-		public static readonly BindableProperty PaddingProperty = BindableProperty.Create("Padding", typeof(Thickness), typeof(Layout), default(Thickness),
-									propertyChanged: (bindable, old, newValue) =>
-									{
-										var layout = (Layout)bindable;
-										layout.UpdateChildrenLayout();
-									}, defaultValueCreator: (bindable) => ((Layout)bindable).CreateDefaultPadding());
+		public static readonly BindableProperty PaddingProperty = PaddingElement.PaddingProperty;
 
 		static IList<KeyValuePair<Layout, int>> s_resolutionList = new List<KeyValuePair<Layout, int>>();
 		static bool s_relayoutInProgress;
@@ -87,15 +82,20 @@ namespace Xamarin.Forms
 
 		public Thickness Padding
 		{
-			get { return (Thickness)GetValue(PaddingProperty); }
-			set { SetValue(PaddingProperty, value); }
+			get { return (Thickness)GetValue(PaddingElement.PaddingProperty); }
+			set { SetValue(PaddingElement.PaddingProperty, value); }
 		}
 
-		internal virtual Thickness CreateDefaultPadding()
+		Thickness IPaddingElement.PaddingDefaultValueCreator()
 		{
 			return default(Thickness);
 		}
 
+		void IPaddingElement.OnPaddingPropertyChanged(Thickness oldValue, Thickness newValue)
+		{
+			UpdateChildrenLayout();
+		}
+
 		internal ObservableCollection<Element> InternalChildren { get; } = new ObservableCollection<Element>();
 
 		internal override ReadOnlyCollection<Element> LogicalChildrenInternal

Xamarin.Forms.Core/PaddingElement.cs

@@ -0,0 +1,65 @@
+namespace Xamarin.Forms
+{
+	static class PaddingElement
+	{
+		public static readonly BindableProperty PaddingProperty =
+			BindableProperty.Create(nameof(IPaddingElement.Padding), typeof(Thickness), typeof(IPaddingElement), default(Thickness),
+									propertyChanged: OnPaddingPropertyChanged,
+									defaultValueCreator: PaddingDefaultValueCreator);
+
+		static void OnPaddingPropertyChanged(BindableObject bindable, object oldValue, object newValue)
+		{
+			((IPaddingElement)bindable).OnPaddingPropertyChanged((Thickness)oldValue, (Thickness)newValue);
+		}
+
+		static object PaddingDefaultValueCreator(BindableObject bindable)
+		{
+			return ((IPaddingElement)bindable).PaddingDefaultValueCreator();
+		}
+
+		public static readonly BindableProperty PaddingLeftProperty =
+			BindableProperty.Create("PaddingLeft", typeof(double), typeof(IPaddingElement), default(double),
+									propertyChanged: OnPaddingLeftChanged);
+
+		static void OnPaddingLeftChanged(BindableObject bindable, object oldValue, object newValue)
+		{
+			var padding = (Thickness)bindable.GetValue(PaddingProperty);
+			padding.Left = (double)newValue;
+			bindable.SetValue(PaddingProperty, padding);
+		}
+
+		public static readonly BindableProperty PaddingTopProperty =
+			BindableProperty.Create("PaddingTop", typeof(double), typeof(IPaddingElement), default(double),
+									propertyChanged: OnPaddingTopChanged);
+
+		static void OnPaddingTopChanged(BindableObject bindable, object oldValue, object newValue)
+		{
+			var padding = (Thickness)bindable.GetValue(PaddingProperty);
+			padding.Top = (double)newValue;
+			bindable.SetValue(PaddingProperty, padding);
+		}
+
+		public static readonly BindableProperty PaddingRightProperty =
+			BindableProperty.Create("PaddingRight", typeof(double), typeof(IPaddingElement), default(double),
+									propertyChanged: OnPaddingRightChanged);
+
+		static void OnPaddingRightChanged(BindableObject bindable, object oldValue, object newValue)
+		{
+			var padding = (Thickness)bindable.GetValue(PaddingProperty);
+			padding.Right = (double)newValue;
+			bindable.SetValue(PaddingProperty, padding);
+		}
+
+		public static readonly BindableProperty PaddingBottomProperty =
+			BindableProperty.Create("PaddingBottom", typeof(double), typeof(IPaddingElement), default(double),
+									propertyChanged: OnPaddingBottomChanged);
+
+		static void OnPaddingBottomChanged(BindableObject bindable, object oldValue, object newValue)
+		{
+			var padding = (Thickness)bindable.GetValue(PaddingProperty);
+			padding.Bottom = (double)newValue;
+			bindable.SetValue(PaddingProperty, padding);
+		}
+
+	}
+}

Xamarin.Forms.Core/Page.cs

@@ -12,7 +12,7 @@ using Xamarin.Forms.Platform;
 namespace Xamarin.Forms
 {
 	[RenderWith(typeof(_PageRenderer))]
-	public class Page : VisualElement, ILayout, IPageController, IElementConfiguration<Page>
+	public class Page : VisualElement, ILayout, IPageController, IElementConfiguration<Page>, IPaddingElement
 	{
 		public const string BusySetSignalName = "Xamarin.BusySet";
 
@@ -26,11 +26,7 @@ namespace Xamarin.Forms
 
 		public static readonly BindableProperty IsBusyProperty = BindableProperty.Create("IsBusy", typeof(bool), typeof(Page), false, propertyChanged: (bo, o, n) => ((Page)bo).OnPageBusyChanged());
 
-		public static readonly BindableProperty PaddingProperty = BindableProperty.Create("Padding", typeof(Thickness), typeof(Page), default(Thickness), propertyChanged: (bindable, old, newValue) =>
-		{
-			var layout = (Page)bindable;
-			layout.UpdateChildrenLayout();
-		});
+		public static readonly BindableProperty PaddingProperty = PaddingElement.PaddingProperty;
 
 		public static readonly BindableProperty TitleProperty = BindableProperty.Create("Title", typeof(string), typeof(Page), null);
 
@@ -76,8 +72,18 @@ namespace Xamarin.Forms
 
 		public Thickness Padding
 		{
-			get { return (Thickness)GetValue(PaddingProperty); }
-			set { SetValue(PaddingProperty, value); }
+			get { return (Thickness)GetValue(PaddingElement.PaddingProperty); }
+			set { SetValue(PaddingElement.PaddingProperty, value); }
+		}
+
+		Thickness IPaddingElement.PaddingDefaultValueCreator()
+		{
+			return default(Thickness);
+		}
+
+		void IPaddingElement.OnPaddingPropertyChanged(Thickness oldValue, Thickness newValue)
+		{
+			UpdateChildrenLayout();
 		}
 
 		public string Title

Xamarin.Forms.Core/Xamarin.Forms.Core.csproj

@@ -476,6 +476,8 @@
     <Compile Include="ReferenceTypeConverter.cs" />
     <Compile Include="ITextAlignmentElement.cs" />
     <Compile Include="TextAlignmentElement.cs" />
+    <Compile Include="PaddingElement.cs" />
+    <Compile Include="IPaddingElement.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildExtensionsPath32)\Microsoft\Portable\$(TargetFrameworkVersion)\Microsoft.Portable.CSharp.targets" />
   <ItemGroup>