Critical crash: Rectangle selection crashes app (VisualLinesInvalidException)

[mx7b7]

Describe the bug
Performing a rectangle selection in AvaloniaEdit (Alt + mouse)
and extending the selection to the right edge of the editor triggers a
VisualLinesInvalidException and crashes the application immediately.

Steps to reproduce

1. Open the AvaloniaEdit demo (v12.0 RC1 or 11.4.x)
2. Select text horizontally with Alt + mouse until you reach the right edge of the editor
3. The app crashes immediately

Expected behavior
Rectangle selection should work correctly, even at the right edge,
without throwing an exception.

Actual behavior
The application crashes with:
Exception of type 'AvaloniaEdit.Rendering.VisualLinesInvalidException' was thrown.
at AvaloniaEdit.Rendering.TextView.get_VisualLines()
at AvaloniaEdit.Rendering.BackgroundGeometryBuilder.GetRectsForSegmentImpl(TextView textView, ISegment segment, Boolean extendToFullWidthAtLineEnd)+MoveNext()
at AvaloniaEdit.Rendering.BackgroundGeometryBuilder.AddSegment(TextView textView, ISegment segment)
at AvaloniaEdit.Editing.SelectionLayer.Render(DrawingContext drawingContext)
at Avalonia.Rendering.Composition.CompositingRenderer.UpdateCore()
at Avalonia.Rendering.Composition.CompositingRenderer.Update()
at Avalonia.Rendering.Composition.Compositor.CommitCore()
at Avalonia.Rendering.Composition.Compositor.Commit()
at Avalonia.Media.MediaContext.CommitCompositor(Compositor compositor)
at Avalonia.Media.MediaContext.CommitCompositorsWithThrottling()
at Avalonia.Media.MediaContext.RenderCore()
at Avalonia.Media.MediaContext.Render()
at Avalonia.Threading.DispatcherOperation.InvokeCore()

Notes

• This crash happens regardless of syntax highlighting (XSHD or TextMate)
• Older version 11.3.0 does not reproduce the crash
• Regression appears in 11.4.x and continues in v12.0 RC1
• App crash occurs immediately on reaching the right edge, even with a single line of text

Environment:

• AvaloniaEdit v11.4.x and v12.0 RC1
• AvaloniaUI v11.3.11and v12.0 RC1
• OS: Windows 10

[textGamex]

I encountered the same problem; however, my application hangs rather than raising an exception.

[mx7b7]

I encountered the same problem; however, my application hangs rather than raising an exception.

The exception is internal to AvaloniaEdit the only way to actually see it (whether the app freezes or crashes) is if the application has a global UnhandledException handler implemented.

[textGamex]

The exception is internal to AvaloniaEdit the only way to actually see it (whether the app freezes or crashes) is if the application has a global UnhandledException handler implemented.

Thanks for clearing that up.

Is there any temporary workaround for now?

[mx7b7]

The exception is internal to AvaloniaEdit the only way to actually see it (whether the app freezes or crashes) is if the application has a global UnhandledException handler implemented.

Thanks for clearing that up.

Is there any temporary workaround for now?

I have temporarily disabled rectangular selection in my project.

textEditor.Options.EnableRectangularSelection = false;