Ensure that viewport calculations for iOS ScrollView account for cont…

…ent insets (dotnet#18277)

* Ensure that viewport calculations for iOS ScrollView account for content insets
Fixes dotnet#17224

* Update baseline image

src/Controls/tests/DeviceTests/Elements/ScrollView/ScrollViewTests.iOS.cs

@@ -7,6 +7,7 @@
 using Microsoft.Maui.Graphics;
 using Microsoft.Maui.Handlers;
 using Microsoft.Maui.Hosting;
+using UIKit;
 using Xunit;
 
 namespace Microsoft.Maui.DeviceTests
@@ -35,5 +36,52 @@ await scrollViewHandler.PlatformView.AttachAndRun(() =>
  });
  });
  }
+
+ [Fact]
+ public async Task ContentSizeExpandsToViewport()
+ {
+ EnsureHandlerCreated(builder => { builder.ConfigureMauiHandlers(handlers => { handlers.AddHandler<Entry, EntryHandler>(); }); });
+
+ var scrollView = new ScrollView();
+
+ var entry = new Entry() { Text = "In a ScrollView", HeightRequest = 10 };
+
+
+ static CoreGraphics.CGSize getViewportSize(UIScrollView scrollView)
+ {
+ return scrollView.AdjustedContentInset.InsetRect(scrollView.Bounds).Size;
+ };
+
+ var scrollViewHandler = await InvokeOnMainThreadAsync(() =>
+ {
+ return CreateHandlerAsync<ScrollViewHandler>(scrollView);
+ });
+
+ await InvokeOnMainThreadAsync(async () =>
+ {
+ await scrollViewHandler.PlatformView.AttachAndRun(async () =>
+ {
+ var uiScrollView = scrollViewHandler.PlatformView;
+
+ uiScrollView.ContentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentBehavior.Always;
+ var parent = uiScrollView.Superview;
+ uiScrollView.Bounds = parent.Bounds;
+ uiScrollView.Center = parent.Center;
+
+ scrollView.Content = entry;
+
+ parent.SetNeedsLayout();
+ parent.LayoutIfNeeded();
+
+ await Task.Yield();
+
+ var contentSize = uiScrollView.ContentSize;
+ var viewportSize = getViewportSize(uiScrollView);
+
+ Assert.Equal(viewportSize.Height, contentSize.Height);
+ Assert.Equal(viewportSize.Width, contentSize.Width);
+ });
+ });
+ }
  }
 }

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

@@ -1,13 +1,7 @@
 using System;
-using System.Collections.Generic;
-using System.ComponentModel;
-using System.Drawing;
-using System.Text;
 using CoreGraphics;
 using Microsoft.Maui.Graphics;
 using Microsoft.Maui.Layouts;
-using Microsoft.Maui.Platform;
-using ObjCRuntime;
 using UIKit;
 using Size = Microsoft.Maui.Graphics.Size;
 
@@ -103,9 +97,11 @@ public static void MapOrientation(IScrollViewHandler handler, IScrollView scroll
  // without having to re-layout the ScrollView
 
  var fullContentSize = scrollView.PresentedContent?.DesiredSize ?? Size.Zero;
- var viewportBounds = uiScrollView.Bounds;
+
+ var viewportBounds = GetViewportBounds(uiScrollView);
  var viewportWidth = viewportBounds.Width;
  var viewportHeight = viewportBounds.Height;
+
  SetContentSizeForOrientation(uiScrollView, viewportWidth, viewportHeight, scrollView.Orientation, fullContentSize);
  }
 
@@ -127,7 +123,7 @@ public static void MapRequestScrollTo(IScrollViewHandler handler, IScrollView sc
  var availableScrollWidth = uiScrollView.ContentSize.Width - uiScrollView.Frame.Width;
  var minScrollHorizontal = Math.Min(request.HorizontalOffset, availableScrollWidth);
  var minScrollVertical = Math.Min(request.VerticalOffset, availableScrollHeight);
- uiScrollView.SetContentOffset(new CoreGraphics.CGPoint(minScrollHorizontal, minScrollVertical), !request.Instant);
+ uiScrollView.SetContentOffset(new CGPoint(minScrollHorizontal, minScrollVertical), !request.Instant);
 
  if (request.Instant)
  {
@@ -185,16 +181,15 @@ static void InsertContentView(UIScrollView platformScrollView, IScrollView scrol
  return;
  }
 
- var contentContainer = new ContentView()
+ var contentContainer = new ContentView
  {
  View = scrollView.PresentedContent,
- Tag = ContentPanelTag
+ Tag = ContentPanelTag,
+ // This is where we normally would inject the cross-platform ScrollView's layout logic; instead, we're injecting the
+ // methods from this handler so it can make some adjustments for things like Padding before the default logic is invoked
+ CrossPlatformLayout = crossPlatformLayout
  };
 
- // This is where we normally would inject the cross-platform ScrollView's layout logic; instead, we're injecting the
- // methods from this handler so it can make some adjustments for things like Padding before the default logic is invoked
- contentContainer.CrossPlatformLayout = crossPlatformLayout;
-
  platformScrollView.ClearSubviews();
  contentContainer.AddSubview(platformContent);
  platformScrollView.AddSubview(contentContainer);
@@ -289,6 +284,11 @@ static void SetContentSizeForOrientation(UIScrollView uiScrollView, double viewp
  uiScrollView.ContentSize = contentSize;
  }
 
+ static CGRect GetViewportBounds(UIScrollView platformScrollView)
+ {
+ return platformScrollView.AdjustedContentInset.InsetRect(platformScrollView.Bounds);
+ }
+
  Size ICrossPlatformLayout.CrossPlatformMeasure(double widthConstraint, double heightConstraint)
  {
  var scrollView = VirtualView;
@@ -301,17 +301,18 @@ Size ICrossPlatformLayout.CrossPlatformMeasure(double widthConstraint, double he
  return Size.Zero;
  }
 
- var scrollViewBounds = platformScrollView.Bounds;
+ var viewPortBounds = GetViewportBounds(platformScrollView);
+
  var padding = scrollView.Padding;
 
  if (widthConstraint == 0)
  {
- widthConstraint = scrollViewBounds.Width;
+ widthConstraint = viewPortBounds.Width;
  }
 
  if (heightConstraint == 0)
  {
- heightConstraint = scrollViewBounds.Height;
+ heightConstraint = viewPortBounds.Height;
  }
 
  // Account for the ScrollView Padding before measuring the content
@@ -330,29 +331,28 @@ Size ICrossPlatformLayout.CrossPlatformArrange(Rect bounds)
  var crossPlatformLayout = scrollView as ICrossPlatformLayout;
  var platformScrollView = PlatformView;
 
- var contentSize = crossPlatformLayout.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 viewportBounds = GetViewportBounds(platformScrollView);
+
+ var contentSize = crossPlatformLayout.CrossPlatformArrange(viewportBounds.ToRectangle());
+
  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)
+ if (container != null)
  {
  // Ensure the container is at least the size of the UIScrollView itself, so that the 
  // cross-platform layout logic makes sense and the contents don't arrange outside the 
  // container. (Everything will look correct if they do, but hit testing won't work properly.)
-
- var scrollViewBounds = uiScrollView.Bounds;
  var containerBounds = contentSize;
 
  container.Bounds = new CGRect(0, 0,
- Math.Max(containerBounds.Width, scrollViewBounds.Width),
- Math.Max(containerBounds.Height, scrollViewBounds.Height));
+ Math.Max(containerBounds.Width, viewportBounds.Width),
+ Math.Max(containerBounds.Height, viewportBounds.Height));
 
  container.Center = new CGPoint(container.Bounds.GetMidX(), container.Bounds.GetMidY());
  }