Resize internal content container when ScrollView content is resized (#16385)

* Resize internal content container when ScrollView content is resized
Fixes #14257

* Fix constructor

Author: hartez

src/Controls/samples/Controls.Sample.UITests/Issues/Issue14257.cs

@@ -0,0 +1,39 @@
+using Microsoft.Maui.Controls;
+
+namespace Maui.Controls.Sample.Issues
+{
+	[Issue(IssueTracker.Github, 14257, "VerticalStackLayout inside Scrollview: Button at the bottom not clickable on IOS", PlatformAffected.iOS)]
+	public class Issue14257 : TestContentPage
+	{
+		protected override void Init()
+		{
+			var scrollView = new ScrollView();
+			var layout = new VerticalStackLayout() { Margin = new Microsoft.Maui.Thickness(10, 40) };
+
+			var description = new Label { Text = "Tap the Resize button; this will force the Test button off the screen. Then tap the Test button; if a Label with the text \"Success\" appears, the test has passed." };
+
+			var resizeButton = new Button() { Text = "Resize", AutomationId = "Resize" };
+			var layoutContent = new Label() { Text = "Content", HeightRequest = 50 };
+			var testButton = new Button() { Text = "Test", AutomationId = "Test" };
+			var resultLabel = new Label() { AutomationId = "Result" };
+
+			layout.Add(description);
+			layout.Add(resizeButton);
+			layout.Add(layoutContent);
+			layout.Add(resultLabel);
+			layout.Add(testButton);
+
+			scrollView.Content = layout;
+			Content = scrollView;
+
+			resizeButton.Clicked += (sender, args) => { 
+				// Resize the ScrollView content so the test button will be off the screen
+				// If the bug is present, this will make the button untappable
+				layoutContent.HeightRequest = 1000; 
+			};
+
+			// Show the Success label if the button is tapped, so we can verify the bug is not present
+			testButton.Clicked += (sender, args) => { resultLabel.Text = "Success"; };
+		}
+	}
+}

src/Controls/tests/UITests/Tests/Issues/Issue14257.cs

@@ -0,0 +1,26 @@
+using Microsoft.Maui.Appium;
+using NUnit.Framework;
+
+namespace Microsoft.Maui.AppiumTests.Issues
+{
+	public class Issue14257 : _IssuesUITest
+	{
+		public Issue14257(TestDevice device) : base(device) { }
+
+		public override string Issue => "VerticalStackLayout inside Scrollview: Button at the bottom not clickable on IOS";
+
+		[Test]
+		public void ResizeScrollViewAndTapButtonTest()
+		{
+			// Tapping the Resize button will change the height of the ScrollView content
+			App.Tap("Resize");
+
+			// Scroll down to the Test button. When the bug is present, the button cannot be tapped.
+			App.ScrollDownTo("Test");
+			App.Tap("Test");
+
+			// If we can successfully tap the button, the Success label will be displayed
+			Assert.IsTrue(App.WaitForTextToBePresentInElement("Result", "Success"));
+		}
+	}
+}

src/Core/src/Handlers/ScrollView/ScrollViewHandler.iOS.cs

@@ -188,36 +188,6 @@ static void InsertContentView(UIScrollView platformScrollView, IScrollView scrol
 			platformScrollView.AddSubview(contentContainer);
 		}
 
-		static Size MeasureScrollViewContent(double widthConstraint, double heightConstraint, Func<double, double, Size> internalMeasure, UIScrollView platformScrollView, IScrollView scrollView)
-		{
-			var presentedContent = scrollView.PresentedContent;
-			if (presentedContent == null)
-			{
-				return Size.Zero;
-			}
-
-			var scrollViewBounds = platformScrollView.Bounds;
-			var padding = scrollView.Padding;
-
-			if (widthConstraint == 0)
-			{
-				widthConstraint = scrollViewBounds.Width;
-			}
-
-			if (heightConstraint == 0)
-			{
-				heightConstraint = scrollViewBounds.Height;
-			}
-
-			// Account for the ScrollView Padding before measuring the content
-			widthConstraint = AccountForPadding(widthConstraint, padding.HorizontalThickness);
-			heightConstraint = AccountForPadding(heightConstraint, padding.VerticalThickness);
-
-			var result = internalMeasure.Invoke(widthConstraint, heightConstraint);
-
-			return result.AdjustForFill(new Rect(0, 0, widthConstraint, heightConstraint), presentedContent);
-		}
-
 		public override Size GetDesiredSize(double widthConstraint, double heightConstraint)
 		{
 			var virtualView = VirtualView;
@@ -338,6 +308,16 @@ Size ICrossPlatformLayout.CrossPlatformArrange(Rect bounds)
 		{
 			var scrollView = VirtualView;
 			var platformScrollView = PlatformView;
+			
+			var contentSize = scrollView.CrossPlatformArrange(bounds);
+
+			// The UIScrollView's bounds are available, so we can use them to make sure the ContentSize makes sense
+			// for the ScrollView orientation
+			var viewportBounds = platformScrollView.Bounds;
+			var viewportHeight = viewportBounds.Height;
+			var viewportWidth = viewportBounds.Width;
+			SetContentSizeForOrientation(platformScrollView, viewportWidth, viewportHeight, scrollView.Orientation, contentSize);
+
 			var container = GetContentView(platformScrollView);
 
 			if (container?.Superview is UIScrollView uiScrollView)
@@ -347,23 +327,15 @@ Size ICrossPlatformLayout.CrossPlatformArrange(Rect bounds)
 				// container. (Everything will look correct if they do, but hit testing won't work properly.)
 
 				var scrollViewBounds = uiScrollView.Bounds;
-				var containerBounds = container.Bounds;
+				var containerBounds = contentSize;
 
 				container.Bounds = new CGRect(0, 0,
 					Math.Max(containerBounds.Width, scrollViewBounds.Width),
 					Math.Max(containerBounds.Height, scrollViewBounds.Height));
+
 				container.Center = new CGPoint(container.Bounds.GetMidX(), container.Bounds.GetMidY());
 			}
 
-			var contentSize = scrollView.CrossPlatformArrange(bounds);
-
-			// The UIScrollView's bounds are available, so we can use them to make sure the ContentSize makes sense
-			// for the ScrollView orientation
-			var viewportBounds = platformScrollView.Bounds;
-			var viewportHeight = viewportBounds.Height;
-			var viewportWidth = viewportBounds.Width;
-			SetContentSizeForOrientation(platformScrollView, viewportWidth, viewportHeight, scrollView.Orientation, contentSize);
-
 			return contentSize;
 		}