NsTextView.ShouldChangeText throws ArgumentNullException

[tipa]

Apple platform

macOS

Framework version

net10.0-*

Affected platform version

macOS 26.0.1 - net10-rc2

Description

When subclassing ShouldChangeText of NSTextView, sometimes null is provided as replacementString. The Apple docs say: ... If only text attributes are being changed, replacementString is nil.

The .NET bindings appear to null-check the parameter and throw an ArgumentNullException when calling the base-method in a subclass:

System.ArgumentNullException: Value cannot be null. (Parameter 'replacementString')

Steps to Reproduce

public partial class ViewController : NSViewController
{
    public override void LoadView()
    {
        var tv = new DelegateDrivenUndoTextView()
        {
            AutoresizingMask = NSViewResizingMask.WidthSizable | NSViewResizingMask.HeightSizable,
            Value = "test"
        };
        View = new NSScrollView { DocumentView = tv };

        tv.SelectAll(this);
        var delay = new CoreFoundation.DispatchTime(CoreFoundation.DispatchTime.Now, TimeSpan.FromMilliseconds(100));
        CoreFoundation.DispatchQueue.MainQueue.DispatchAfter(delay, () =>
        {
            NSFontManager.SharedFontManager.PerformSelector(new Selector("addFontTrait:"),
                NSNumber.FromInt32((int)NSFontTraitMask.Bold));
        });
    }
}

sealed class DelegateDrivenUndoTextView : NSTextView
{
    public override bool ShouldChangeText(NSRange affectedCharRange, string replacementString)
    {
        return base.ShouldChangeText(affectedCharRange, replacementString);
    }
}

Example project: test_nstextview.zip

Did you find any workaround?

I can check for this case, but it shows a warning:

Additionally, doing this causes the NSTextView's undo manager not register the trait change and it cannot be undone without further customization

[rolfbjarne]

Thanks for the report! I can confirm the issue, and I'll get this fixed.