You are right, Point is incorrectly exposing "x" and "y" properties (lowercase).

But I see that Rect class is properly exposing "X", "Y", "Width" and "Height", even in 3.1.4. Could you please paste your converter here?

I'm sorry, I double-checked and indeed, X, Y, Width and Height properties of the Rect can be used with binding. However, other properties like IsEmpty, Top, Bottom, Location etc. still can not be bound to. It was some time ago, so I've confused the exact names of the properties that were causing problems. I've used a simple converter to extract the properties I needed:

public class RectPropertyConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value == DependencyProperty.UnsetValue)
return DependencyProperty.UnsetValue;

        var r = (Rect)value;
        return parameter switch
        {
            nameof(r.Width) => r.Width,
            nameof(r.Height) => r.Height,
            nameof(r.Left) => r.Left,
            nameof(r.Right) => r.Right,
            nameof(r.Top) => r.Top,
            nameof(r.Bottom) => r.Bottom,
            nameof(r.X) => r.X,
            nameof(r.Y) => r.Y,
            nameof(r.Location) => r.Location,
            nameof(r.Size) => r.Size,
            nameof(r.TopLeft) => r.TopLeft,
            nameof(r.TopRight) => r.TopRight,
            nameof(r.BottomLeft) => r.BottomLeft,
            nameof(r.BottomRight) => r.BottomRight,
            _ => r
        };
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

Thanks for this!

Properties renamed to "X" and "Y"
Added IsEmpty, Left, Top, Right, Bottom To Rect. Unfortunately, the other properties can't be added until the next reflection system.

Thanks for your feedback!