Fix RTL in AbsoluteLayout (#7309)

* Add AbsoluteLayoutManager RTL tests

* First attempt at fix

* Fix up tests and RTL math

* Remove unnecessary using

* Remove unneeded and wrong code

src/Core/src/Layouts/AbsoluteLayoutManager.cs

@@ -60,11 +60,14 @@ public override Size ArrangeChildren(Rect bounds)
 		{
 			var padding = AbsoluteLayout.Padding;
 
-			double top = padding.Top + bounds.Y;
-			double left = padding.Left + bounds.X;
+			double top = padding.Top + bounds.Top;
+			double left = padding.Left + bounds.Left;
+			double right = bounds.Right - padding.Right;
 			double availableWidth = bounds.Width - padding.HorizontalThickness;
 			double availableHeight = bounds.Height - padding.VerticalThickness;
 
+			bool leftToRight = AbsoluteLayout.ShouldArrangeLeftToRight();
+
 			for (int n = 0; n < AbsoluteLayout.Count; n++)
 			{
 				var child = AbsoluteLayout[n];
@@ -93,7 +96,12 @@ public override Size ArrangeChildren(Rect bounds)
 					destination.Y = (availableHeight - destination.Height) * destination.Y;
 				}
 
-				destination.X += left;
+				// Figure out where we're starting from (the left edge of the padded area, or the right edge)
+				if (leftToRight)
+					destination.X += left;
+				else
+					destination.X = right - destination.X - destination.Width;
+
 				destination.Y += top;
 
 				child.Arrange(destination);

src/Core/tests/UnitTests/Layouts/AbsoluteLayoutManagerTests.cs

@@ -445,5 +445,47 @@ public void ChildMeasureRespectsProportionalBounds()
 
 			child.Received().Measure(Arg.Is(expectedWidth * widthConstraint), Arg.Is(expectedHeight * heightConstraint));
 		}
+
+		[Fact(DisplayName = "First View in LTR Absolute Layout is on the left")]
+		public void LtrShouldHaveFirstItemOnTheLeft()
+		{
+			var abs = CreateTestLayout();
+			var child = CreateTestView();
+			SubstituteChildren(abs, child);
+			var childBounds = new Rect(10, 0, 100, 100);
+			SetLayoutBounds(abs, child, childBounds);
+
+			abs.FlowDirection.Returns(FlowDirection.LeftToRight);
+
+			var manager = new AbsoluteLayoutManager(abs);
+			var measuredSize = manager.Measure(double.PositiveInfinity, 100);
+			manager.ArrangeChildren(new Rect(Point.Zero, measuredSize));
+
+			// We expect that the view should be arranged on the left
+			var expectedRectangle = new Rect(10, 0, 100, 100);
+
+			abs[0].Received().Arrange(Arg.Is(expectedRectangle));
+		}
+
+		[Fact(DisplayName = "First View in RTL Absolute Layout is on the right")]
+		public void RtlShouldHaveFirstItemOnTheRight()
+		{
+			var abs = CreateTestLayout();
+			var child = CreateTestView();
+			SubstituteChildren(abs, child);
+			var childBounds = new Rect(10, 0, 100, 100);
+			SetLayoutBounds(abs, child, childBounds);
+
+			abs.FlowDirection.Returns(FlowDirection.RightToLeft);
+
+			var manager = new AbsoluteLayoutManager(abs);
+			var measuredSize = manager.Measure(double.PositiveInfinity, 100);
+			manager.ArrangeChildren(new Rect(Point.Zero, measuredSize));
+
+			// We expect that the view should be arranged on the right
+			var expectedRectangle = new Rect(0, 0, 100, 100);
+
+			abs[0].Received().Arrange(Arg.Is(expectedRectangle));
+		}
 	}
 }