[WinRT/UWP] Adjust margin for centered Slider

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla29110.cs

@@ -0,0 +1,49 @@
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+#if UITEST
+using Xamarin.UITest;
+using NUnit.Framework;
+#endif
+
+// Apply the default category of "Issues" to all of the tests in this assembly
+// We use this as a catch-all for tests which haven't been individually categorized
+#if UITEST
+[assembly: NUnit.Framework.Category("Issues")]
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Bugzilla, 29110, "[WinRT/UWP] VerticalOptions = LayoutOptions.Center or CenterAndExpand on Sliders does not result in centered display", PlatformAffected.WinRT)]
+	public class Bugzilla29110 : TestContentPage
+	{
+		protected override void Init()
+		{
+			Content = new StackLayout
+			{
+				Orientation = StackOrientation.Horizontal,
+				HorizontalOptions = LayoutOptions.FillAndExpand,
+				Children =
+				{
+					new Label
+					{
+						BackgroundColor = Color.CadetBlue,
+						HorizontalOptions = LayoutOptions.Start,
+						VerticalOptions = LayoutOptions.CenterAndExpand,
+						VerticalTextAlignment = TextAlignment.Center,
+						Text = "Label"
+					},
+					new Slider
+					{
+						BackgroundColor = Color.Green,
+						HorizontalOptions = LayoutOptions.FillAndExpand,
+						VerticalOptions = LayoutOptions.CenterAndExpand,
+						Minimum = 0,
+						Maximum = 100
+					}
+				}
+			};
+		}
+	}
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems

@@ -39,6 +39,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla29107.xaml.cs">
       <DependentUpon>Bugzilla29107.xaml</DependentUpon>
     </Compile>
+    <Compile Include="$(MSBuildThisFileDirectory)Bugzilla29110.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla29158.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla29363.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla29229.cs" />

Xamarin.Forms.Platform.WinRT/SliderRenderer.cs

@@ -1,5 +1,6 @@
 using System;
 using System.ComponentModel;
+using Windows.UI.Xaml;
 using Windows.UI.Xaml.Controls.Primitives;
 
 #if WINDOWS_UWP
@@ -24,6 +25,25 @@ protected override void OnElementChanged(ElementChangedEventArgs<Slider> e)
 					SetNativeControl(slider);
 
 					slider.ValueChanged += OnNativeValueCHanged;
+
+					// Even when using Center/CenterAndExpand, a Slider has an oddity where it looks
+					// off-center in its layout by a smidge. The default templates are slightly different
+					// between 8.1/UWP; the 8.1 rows are 17/Auto/32 and UWP are 18/Auto/18. The value of
+					// the hardcoded 8.1 rows adds up to 49 (when halved is 24.5) and UWP are 36 (18). Using
+					// a difference of about 6 pixels to correct this oddity seems to make them both center
+					// more correctly.
+					//
+					// The VerticalAlignment needs to be set as well since a control would not actually be
+					// centered if a larger HeightRequest is set.
+					if (Element.VerticalOptions.Alignment == LayoutAlignment.Center && Control.Orientation == Windows.UI.Xaml.Controls.Orientation.Horizontal)
+					{
+						Control.VerticalAlignment = VerticalAlignment.Center;
+#if WINDOWS_UWP
+						slider.Margin = new Windows.UI.Xaml.Thickness(0, 7, 0, 0);
+#else
+						slider.Margin = new Windows.UI.Xaml.Thickness(0, 13, 0, 0);
+#endif
+					}
 				}
 
 				double stepping = Math.Min((e.NewElement.Maximum - e.NewElement.Minimum) / 10, 1);