[All] Basic Accessibility Support (#713)

* [Core] Add accessibility properties

* [Controls] Add accessibility gallery

* [iOS] Implement accessibility properties

* [Android] Implement accessibilty properties

* [Win] Implement accessibility properties

* [Win] Select ListView item on selected for a11y

* Update docs

* TODO: macOS accessibility

* [iOS] Fix failing UI Tests

1 files changed, 98 insertions, 0 deletions

diff --git a/Xamarin.Forms.Platform.WinRT/ViewRenderer.cs b/Xamarin.Forms.Platform.WinRT/ViewRenderer.cs
index 148da1b3..0017531f 100644
--- a/Xamarin.Forms.Platform.WinRT/ViewRenderer.cs
+++ b/Xamarin.Forms.Platform.WinRT/ViewRenderer.cs
@@ -1,5 +1,6 @@
 using Windows.UI.Xaml;
 using Windows.UI.Xaml.Automation;
+using Windows.UI.Xaml.Automation.Peers;
 
 #if WINDOWS_UWP
 
@@ -11,6 +12,11 @@ namespace Xamarin.Forms.Platform.WinRT
 {
 	public class ViewRenderer<TElement, TNativeElement> : VisualElementRenderer<TElement, TNativeElement> where TElement : View where TNativeElement : FrameworkElement
 	{
+		string _defaultAutomationPropertiesName;
+		AccessibilityView? _defaultAutomationPropertiesAccessibilityView;
+		string _defaultAutomationPropertiesHelpText;
+		UIElement _defaultAutomationPropertiesLabeledBy;
+
 		protected override void OnElementChanged(ElementChangedEventArgs<TElement> e)
 		{
 			base.OnElementChanged(e);
@@ -33,5 +39,97 @@ namespace Xamarin.Forms.Platform.WinRT
 				Control.SetValue(AutomationProperties.AutomationIdProperty, id);
 			}
 		}
+		protected override void SetAutomationPropertiesName()
+		{
+			if (Control == null)
+			{
+				base.SetAutomationPropertiesName();
+				return;
+			}
+
+			if (Element == null)
+				return;
+
+			if (_defaultAutomationPropertiesName == null)
+				_defaultAutomationPropertiesName = (string)Control.GetValue(AutomationProperties.NameProperty);
+
+			var elemValue = (string)Element.GetValue(Accessibility.NameProperty);
+
+			if (!string.IsNullOrWhiteSpace(elemValue))
+				Control.SetValue(AutomationProperties.NameProperty, elemValue);
+			else
+				Control.SetValue(AutomationProperties.NameProperty, _defaultAutomationPropertiesName);
+		}
+
+		protected override void SetAutomationPropertiesAccessibilityView()
+		{
+			if (Control == null)
+			{
+				base.SetAutomationPropertiesAccessibilityView();
+				return;
+			}
+
+			if (Element == null)
+				return;
+
+			if (!_defaultAutomationPropertiesAccessibilityView.HasValue)
+				_defaultAutomationPropertiesAccessibilityView = (AccessibilityView)Control.GetValue(AutomationProperties.AccessibilityViewProperty);
+
+			var newValue = _defaultAutomationPropertiesAccessibilityView;
+			var elemValue = (bool?)Element.GetValue(Accessibility.IsInAccessibleTreeProperty);
+
+			if (elemValue == true)
+				newValue = AccessibilityView.Content;
+			else if (elemValue == false)
+				newValue = AccessibilityView.Raw;
+
+			Control.SetValue(AutomationProperties.AccessibilityViewProperty, newValue);
+		}
+
+		protected override void SetAutomationPropertiesHelpText()
+		{
+			if (Control == null)
+			{
+				base.SetAutomationPropertiesHelpText();
+				return;
+			}
+
+			if (Element == null)
+				return;
+
+			if (_defaultAutomationPropertiesHelpText == null)
+				_defaultAutomationPropertiesHelpText = (string)Control.GetValue(AutomationProperties.HelpTextProperty);
+
+			var elemValue = (string)Element.GetValue(Accessibility.HintProperty);
+
+			if (!string.IsNullOrWhiteSpace(elemValue))
+				Control.SetValue(AutomationProperties.HelpTextProperty, elemValue);
+			else
+				Control.SetValue(AutomationProperties.HelpTextProperty, _defaultAutomationPropertiesHelpText);
+		}
+
+		protected override void SetAutomationPropertiesLabeledBy()
+		{
+			if (Control == null)
+			{
+				base.SetAutomationPropertiesLabeledBy(); 
+				return;
+			}
+
+			if (Element == null)
+				return;
+
+			if (_defaultAutomationPropertiesLabeledBy == null)
+				_defaultAutomationPropertiesLabeledBy = (UIElement)Control.GetValue(AutomationProperties.LabeledByProperty);
+
+			var elemValue = (VisualElement)Element.GetValue(Accessibility.LabeledByProperty);
+			var renderer = elemValue?.GetOrCreateRenderer();
+			var nativeElement = renderer?.GetNativeElement();
+
+			if (nativeElement != null)
+				Control.SetValue(AutomationProperties.LabeledByProperty, nativeElement);
+			else
+				Control.SetValue(AutomationProperties.LabeledByProperty, _defaultAutomationPropertiesLabeledBy);
+		}
 	}
 }
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