UI tests for InputTransparent and fixes for Android/Windows (#808)

* Set up automated UI tests for InputTransparent

* Pull in Adrian's UI tests from PR 483

* Fix bugs with box/label/image gestures passing through when not transparent

* Fix disabling of layouts on Windows; fix 44096 test for iOS/Windows;

* Automate the 53445 test

1 files changed, 44 insertions, 0 deletions

diff --git a/Xamarin.Forms.Platform.Android/Platform.cs b/Xamarin.Forms.Platform.Android/Platform.cs
index ca0b9708..0fc287c9 100644
--- a/Xamarin.Forms.Platform.Android/Platform.cs
+++ b/Xamarin.Forms.Platform.Android/Platform.cs
@@ -1024,6 +1024,50 @@ namespace Xamarin.Forms.Platform.Android
 
 		internal class DefaultRenderer : VisualElementRenderer<View>
 		{
+			bool _notReallyHandled;
+			internal void NotifyFakeHandling()
+			{
+				_notReallyHandled = true;
+			}
+
+			public override bool DispatchTouchEvent(MotionEvent e)
+			{
+				#region
+				// Normally dispatchTouchEvent feeds the touch events to its children one at a time, top child first,
+				// (and only to the children in the hit-test area of the event) stopping as soon as one of them has handled
+				// the event. 
+
+				// But to be consistent across the platforms, we don't want this behavior; if an element is not input transparent
+				// we don't want an event to "pass through it" and be handled by an element "behind/under" it. We just want the processing
+				// to end after the first non-transparent child, regardless of whether the event has been handled.
+
+				// This is only an issue for a couple of controls; the interactive controls (switch, button, slider, etc) already "handle" their touches 
+				// and the events don't propagate to other child controls. But for image, label, and box that doesn't happen. We can't have those controls 
+				// lie about their events being handled because then the events won't propagate to *parent* controls (e.g., a frame with a label in it would
+				// never get a tap gesture from the label). In other words, we *want* parent propagation, but *do not want* sibling propagation. So we need to short-circuit 
+				// base.DispatchTouchEvent here, but still return "false".
+
+				// Duplicating the logic of ViewGroup.dispatchTouchEvent and modifying it slightly for our purposes is a non-starter; the method is too
+				// complex and does a lot of micro-optimization. Instead, we provide a signalling mechanism for the controls which don't already "handle" touch
+				// events to tell us that they will be lying about handling their event; they then return "true" to short-circuit base.DispatchTouchEvent.
+
+				// The container gets this message and after it gets the "handled" result from dispatchTouchEvent, 
+				// it then knows to ignore that result and return false/unhandled. This allows the event to propagate up the tree.
+				#endregion
+
+				_notReallyHandled = false;
+
+				var result = base.DispatchTouchEvent(e);
+
+				if (result && _notReallyHandled)
+				{
+					// If the child control returned true from its touch event handler but signalled that it was a fake "true", leave the event unhandled
+					// so parent controls have the opportunity
+					return false;
+				}
+
+				return result;
+			}
 		}
 
 		#region IPlatformEngine implementation