[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

8 files changed, 211 insertions, 1 deletions

diff --git a/Xamarin.Forms.Platform.Android/AppCompat/FrameRenderer.cs b/Xamarin.Forms.Platform.Android/AppCompat/FrameRenderer.cs
index 1092f767..6954654b 100644
--- a/Xamarin.Forms.Platform.Android/AppCompat/FrameRenderer.cs
+++ b/Xamarin.Forms.Platform.Android/AppCompat/FrameRenderer.cs
@@ -21,6 +21,7 @@ namespace Xamarin.Forms.Platform.Android.AppCompat
 
 		float _defaultElevation = -1f;
 		float _defaultCornerRadius = -1f;
+		int? _defaultLabelFor;
 
 		bool _clickable;
 		bool _disposed;
@@ -106,6 +107,14 @@ namespace Xamarin.Forms.Platform.Android.AppCompat
 				ContentDescription = Element.AutomationId;
 		}
 
+		void IVisualElementRenderer.SetLabelFor(int? id)
+		{
+			if (_defaultLabelFor == null)
+				_defaultLabelFor = LabelFor;
+
+			LabelFor = (int)(id ?? _defaultLabelFor);
+		}
+
 		VisualElementTracker IVisualElementRenderer.Tracker => _visualElementTracker;
 
 		void IVisualElementRenderer.UpdateLayout()
diff --git a/Xamarin.Forms.Platform.Android/AppCompat/MasterDetailPageRenderer.cs b/Xamarin.Forms.Platform.Android/AppCompat/MasterDetailPageRenderer.cs
index 757a98b4..85ab6b73 100644
--- a/Xamarin.Forms.Platform.Android/AppCompat/MasterDetailPageRenderer.cs
+++ b/Xamarin.Forms.Platform.Android/AppCompat/MasterDetailPageRenderer.cs
@@ -165,6 +165,10 @@ namespace Xamarin.Forms.Platform.Android.AppCompat
 				_tracker = new VisualElementTracker(this);
 		}
 
+		void IVisualElementRenderer.SetLabelFor(int? id)
+		{
+		}
+
 		VisualElementTracker IVisualElementRenderer.Tracker => _tracker;
 
 		void IVisualElementRenderer.UpdateLayout()
diff --git a/Xamarin.Forms.Platform.Android/IVisualElementRenderer.cs b/Xamarin.Forms.Platform.Android/IVisualElementRenderer.cs
index 99393516..da565ce2 100644
--- a/Xamarin.Forms.Platform.Android/IVisualElementRenderer.cs
+++ b/Xamarin.Forms.Platform.Android/IVisualElementRenderer.cs
@@ -17,6 +17,9 @@ namespace Xamarin.Forms.Platform.Android
 		SizeRequest GetDesiredSize(int widthConstraint, int heightConstraint);
 
 		void SetElement(VisualElement element);
+
+		void SetLabelFor(int? id);
+
 		void UpdateLayout();
 	}
 }
\ No newline at end of file
diff --git a/Xamarin.Forms.Platform.Android/Renderers/MasterDetailRenderer.cs b/Xamarin.Forms.Platform.Android/Renderers/MasterDetailRenderer.cs
index ec9c620e..d18781a7 100644
--- a/Xamarin.Forms.Platform.Android/Renderers/MasterDetailRenderer.cs
+++ b/Xamarin.Forms.Platform.Android/Renderers/MasterDetailRenderer.cs
@@ -287,6 +287,10 @@ namespace Xamarin.Forms.Platform.Android
 			SetDrawerLockMode(_page.IsGestureEnabled ? LockModeUnlocked : LockModeLockedClosed);
 		}
 
+		void IVisualElementRenderer.SetLabelFor(int? id)
+		{
+		}
+
 		void SetLockMode(int lockMode)
 		{
 			if (_currentLockMode != lockMode)
diff --git a/Xamarin.Forms.Platform.Android/Renderers/ScrollViewRenderer.cs b/Xamarin.Forms.Platform.Android/Renderers/ScrollViewRenderer.cs
index 6db51c23..a2e3ddb3 100644
--- a/Xamarin.Forms.Platform.Android/Renderers/ScrollViewRenderer.cs
+++ b/Xamarin.Forms.Platform.Android/Renderers/ScrollViewRenderer.cs
@@ -328,6 +328,10 @@ namespace Xamarin.Forms.Platform.Android
 			}
 		}
 
+		void IVisualElementRenderer.SetLabelFor(int? id)
+		{
+		}
+
 		void UpdateBackgroundColor()
 		{
 			SetBackgroundColor(Element.BackgroundColor.ToAndroid(Color.Transparent));
diff --git a/Xamarin.Forms.Platform.Android/ViewRenderer.cs b/Xamarin.Forms.Platform.Android/ViewRenderer.cs
index c4bd3fa0..31a9c282 100644
--- a/Xamarin.Forms.Platform.Android/ViewRenderer.cs
+++ b/Xamarin.Forms.Platform.Android/ViewRenderer.cs
@@ -19,6 +19,9 @@ namespace Xamarin.Forms.Platform.Android
 		}
 
 		ViewGroup _container;
+		string _defaultContentDescription;
+		bool? _defaultFocusable;
+		string _defaultHint;
 
 		bool _disposed;
 		EventHandler<VisualElement.FocusRequestArgs> _focusChangeHandler;
@@ -66,7 +69,7 @@ namespace Xamarin.Forms.Platform.Android
 		{
 			if (Control == null)
 				return (base.GetDesiredSize(widthConstraint, heightConstraint));
-				        
+
 			AView view = _container == this ? (AView)Control : _container;
 			view.Measure(widthConstraint, heightConstraint);
 
@@ -124,6 +127,8 @@ namespace Xamarin.Forms.Platform.Android
 
 			if (e.PropertyName == VisualElement.IsEnabledProperty.PropertyName)
 				UpdateIsEnabled();
+			else if (e.PropertyName == Accessibility.LabeledByProperty.PropertyName)
+				SetLabeledBy();
 		}
 
 		protected override void OnLayout(bool changed, int l, int t, int r, int b)
@@ -155,6 +160,79 @@ namespace Xamarin.Forms.Platform.Android
 			}
 		}
 
+		protected override void SetContentDescription()
+		{
+			if (Control == null)
+			{
+				base.SetContentDescription();
+				return;
+			}
+
+			if (Element == null)
+				return;
+
+			if (SetHint())
+				return;
+
+			if (_defaultContentDescription == null)
+				_defaultContentDescription = Control.ContentDescription;
+
+			var elemValue = string.Join(" ", (string)Element.GetValue(Accessibility.NameProperty), (string)Element.GetValue(Accessibility.HintProperty));
+
+			if (!string.IsNullOrWhiteSpace(elemValue))
+				Control.ContentDescription = elemValue;
+			else
+				Control.ContentDescription = _defaultContentDescription;
+		}
+
+		protected override void SetFocusable()
+		{
+			if (Control == null)
+			{
+				base.SetFocusable();
+				return;
+			}
+
+			if (Element == null)
+				return;
+
+			if (!_defaultFocusable.HasValue)
+				_defaultFocusable = Control.Focusable;
+
+			Control.Focusable = (bool)((bool?)Element.GetValue(Accessibility.IsInAccessibleTreeProperty) ?? _defaultFocusable);
+		}
+
+		protected override bool SetHint()
+		{				
+			if (Control == null)
+			{
+				return base.SetHint();
+			}
+
+			if (Element == null)
+				return false;
+
+			var textView = Control as global::Android.Widget.TextView;
+			if (textView == null)
+				return false;
+
+			// Let the specified Title/Placeholder take precedence, but don't set the ContentDescription (won't work anyway)
+			if (((Element as Picker)?.Title ?? (Element as Entry)?.Placeholder ?? (Element as EntryCell)?.Placeholder) != null)
+				return true;
+
+			if (_defaultHint == null)
+				_defaultHint = textView.Hint;
+
+			var elemValue = string.Join(". ", (string)Element.GetValue(Accessibility.NameProperty), (string)Element.GetValue(Accessibility.HintProperty));
+
+			if (!string.IsNullOrWhiteSpace(elemValue))
+				textView.Hint = elemValue;
+			else
+				textView.Hint = _defaultHint;
+
+			return true;
+		}
+
 		protected void SetNativeControl(TNativeView control)
 		{
 			SetNativeControl(control, this);
@@ -219,6 +297,25 @@ namespace Xamarin.Forms.Platform.Android
 			Control.OnFocusChangeListener = this;
 
 			UpdateIsEnabled();
+			SetLabeledBy();
+		}
+
+		void SetLabeledBy()
+		{
+			if (Element == null || Control == null)
+				return;
+
+			var elemValue = (VisualElement)Element.GetValue(Accessibility.LabeledByProperty);
+
+			if (elemValue != null)
+			{
+				var id = Control.Id;
+				if (id == -1)
+					id = Control.Id = FormsAppCompatActivity.GetUniqueId();
+
+				var renderer = elemValue?.GetRenderer();
+				renderer?.SetLabelFor(id);
+			}
 		}
 
 		void UpdateIsEnabled()
diff --git a/Xamarin.Forms.Platform.Android/VisualElementExtensions.cs b/Xamarin.Forms.Platform.Android/VisualElementExtensions.cs
index 13f2fffa..800a967e 100644
--- a/Xamarin.Forms.Platform.Android/VisualElementExtensions.cs
+++ b/Xamarin.Forms.Platform.Android/VisualElementExtensions.cs
@@ -1,7 +1,19 @@
+using System;
+
 namespace Xamarin.Forms.Platform.Android
 {
 	public static class VisualElementExtensions
 	{
+		public static IVisualElementRenderer GetRenderer(this VisualElement self)
+		{
+			if (self == null)
+				throw new ArgumentNullException("self");
+
+			IVisualElementRenderer renderer = Platform.GetRenderer(self);
+
+			return renderer;
+		}
+
 		public static bool ShouldBeMadeClickable(this View view)
 		{
 			var shouldBeClickable = false;
diff --git a/Xamarin.Forms.Platform.Android/VisualElementRenderer.cs b/Xamarin.Forms.Platform.Android/VisualElementRenderer.cs
index 19b05e2e..46bab02e 100644
--- a/Xamarin.Forms.Platform.Android/VisualElementRenderer.cs
+++ b/Xamarin.Forms.Platform.Android/VisualElementRenderer.cs
@@ -23,6 +23,10 @@ namespace Xamarin.Forms.Platform.Android
 
 		VisualElementRendererFlags _flags = VisualElementRendererFlags.AutoPackage | VisualElementRendererFlags.AutoTrack;
 
+		string _defaultContentDescription;
+		bool? _defaultFocusable;
+		string _defaultHint;
+		int? _defaultLabelFor;
 		InnerGestureListener _gestureListener;
 		VisualElementPackager _packager;
 		PropertyChangedEventHandler _propertyChangeHandler;
@@ -209,6 +213,9 @@ namespace Xamarin.Forms.Platform.Android
 			if (element != null && !string.IsNullOrEmpty(element.AutomationId))
 				SetAutomationId(element.AutomationId);
 
+			SetContentDescription();
+			SetFocusable();
+
 			Performance.Stop();
 		}
 
@@ -302,6 +309,12 @@ namespace Xamarin.Forms.Platform.Android
 				UpdateBackgroundColor();
 			else if (e.PropertyName == VisualElement.InputTransparentProperty.PropertyName)
 				InputTransparent = Element.InputTransparent;
+			else if (e.PropertyName == Accessibility.HintProperty.PropertyName)
+				SetContentDescription();
+			else if (e.PropertyName == Accessibility.NameProperty.PropertyName)
+				SetContentDescription();
+			else if (e.PropertyName == Accessibility.IsInAccessibleTreeProperty.PropertyName)
+				SetFocusable();
 		}
 
 		protected override void OnLayout(bool changed, int l, int t, int r, int b)
@@ -331,6 +344,62 @@ namespace Xamarin.Forms.Platform.Android
 			ContentDescription = id;
 		}
 
+		protected virtual void SetContentDescription()
+		{
+			if (Element == null)
+				return;
+
+			if (SetHint())
+				return;
+
+			if (_defaultContentDescription == null)
+				_defaultContentDescription = ContentDescription;
+
+			var elemValue = string.Join(" ", (string)Element.GetValue(Accessibility.NameProperty), (string)Element.GetValue(Accessibility.HintProperty));
+
+			if (!string.IsNullOrWhiteSpace(elemValue))
+				ContentDescription = elemValue;
+			else
+				ContentDescription = _defaultContentDescription;
+		}
+
+		protected virtual void SetFocusable()
+		{
+			if (Element == null)
+				return;
+
+			if (!_defaultFocusable.HasValue)
+				_defaultFocusable = Focusable;
+
+			Focusable = (bool)((bool?)Element.GetValue(Accessibility.IsInAccessibleTreeProperty) ?? _defaultFocusable);
+		}
+
+		protected virtual bool SetHint()
+		{
+			if (Element == null)
+				return false;
+
+			var textView = this as global::Android.Widget.TextView;
+			if (textView == null)
+				return false;
+
+			// Let the specified Title/Placeholder take precedence, but don't set the ContentDescription (won't work anyway)
+			if (((Element as Picker)?.Title ?? (Element as Entry)?.Placeholder ?? (Element as EntryCell)?.Placeholder) != null)
+				return true;
+
+			if (_defaultHint == null)
+				_defaultHint = textView.Hint;
+
+			var elemValue = string.Join(". ", (string)Element.GetValue(Accessibility.NameProperty), (string)Element.GetValue(Accessibility.HintProperty));
+
+			if (!string.IsNullOrWhiteSpace(elemValue))
+				textView.Hint = elemValue;
+			else
+				textView.Hint = _defaultHint;
+
+			return true;
+		}
+
 		protected void SetPackager(VisualElementPackager packager)
 		{
 			_packager = packager;
@@ -357,6 +426,14 @@ namespace Xamarin.Forms.Platform.Android
 			UpdateGestureRecognizers();
 		}
 
+		void IVisualElementRenderer.SetLabelFor(int? id)
+		{
+			if (_defaultLabelFor == null)
+				_defaultLabelFor = LabelFor;
+
+			LabelFor = (int)(id ?? _defaultLabelFor);
+		}
+
 		void SubscribeGestureRecognizers(VisualElement element)
 		{
 			var view = element as View;