[iOS] Bugfix/22469 ios label crash

[artemvalieiev]

Description of Change

I have found an alternative approach for calculating span regions to prevent crashes. Please try launching Issue22469 UITest with using original FormattedStringExtensions on the iPhone 15/XS simulator to reproduce the crash.

System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection. (Parameter 'index')
   at System.Collections.Generic.List`1[[System.Double, System.Private.CoreLib, Version=8.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].get_Item(Int32 index)
   at Microsoft.Maui.Controls.Platform.FormattedStringExtensions.CreateSpanRects(CGRect startRect, CGRect endRect, List`1 lineHeights, List`1 multilineRects, Boolean endsWithNewLine)
   at Microsoft.Maui.Controls.Platform.FormattedStringExtensions.GetMultilinedBounds(NSRange characterRange, NSLayoutManager layoutManager, NSTextContainer textContainer, CGRect startRect, CGRect endRect, List`1 lineHeights, Boolean endsWithNewLine)
   at Microsoft.Maui.Controls.Platform.FormattedStringExtensions.RecalculateSpanPositions(UILabel control, Label element)
   at Microsoft.Maui.Controls.Label.RecalculateSpanPositions()
   at Microsoft.Maui.Controls.Label.ArrangeOverride(Rect bounds)
   at Microsoft.Maui.Controls.VisualElement.Microsoft.Maui.IView.Arrange(Rect bounds)
   at Microsoft.Maui.Layouts.GridLayoutManager.ArrangeChildren(Rect bounds)
   at Microsoft.Maui.Controls.Layout.CrossPlatformArrange(Rect bounds)
   at Microsoft.Maui.Platform.MauiView.CrossPlatformArrange(Rect bounds)
   at Microsoft.Maui.Platform.MauiView.LayoutSubviews()
   at UIKit.UIApplication.UIApplicationMain(Int32 argc, String[] argv, IntPtr principalClassName, IntPtr delegateClassName) in /Users/builder/azdo/_work/1/s/xamarin-macios/src/UIKit/UIApplication.cs:line 58

In the original approach, the DefaultLineHeight is calculated and used to determine the number of text lines associated with the span, which is different from the number of lines returned by EnumerateLineFragments -> multilineRects. This causes an "argument out of range" exception in the loop at line 249, where the loop assumes that the line height count is equal to multilineRects.Count.

Instead, I am always using EnumerateLineFragments and I am trying to calculate each rect depending on line glyph indexes of this line fragment.

Video of Label controls page tests
https://github.com/dotnet/maui/assets/3391032/93f67658-71a5-4705-ab89-71004f4ad2d7

Issues Fixed

Fixes #22469

[artemvalieiev]

I just tried UI test from #22213 , and it works well too with my changes

[artemvalieiev]

I'm guessing this would require verification from Javier @jsuarezruiz anyway

[PureWeen]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[artemvalieiev]

Also fixes #22480 , since using GetBoundingRect for getting text/glyph range rectangle is RTL/LTR independent