NSTokenField selection list shows empty space while scrolling

Question

While using NSTokenField something strange is happening, as shown in the images below :

As I type A, selection from popup is shown.

I scrolled it

Some more scroll, and it went below the visible area.

This is a behaviour with all the tableviews. The view behind the rows are visible , but it automatically springs to normal position. But not in this case.

It is fine in Mail app, it is working fine.

My implementation is :

1. Created an NSTokenField.

2. Set its delegate to AppDelegate.

3. In the implementation file

    -(NSArray *)tokenField:(NSTokenField *)tokenField completionsForSubstring:(NSString *)substring indexOfToken:(NSInteger)tokenIndex indexOfSelectedItem:(NSInteger *)selectedIndex{
       return @[@"A",@"B",@"C"];
   }
   

Even the sample code from apple documentation behaves incorrectly.

How can I make it auto-spring or restrict by some code?

Answer 1

What you see in Mail.app is not an actual NSMenu (Apple cheats, shocking!). Turns out, it's actually a custom NSTextField linked to an NSTableView stuck in a transparent window.

It's a fairly old trick to get around the extremely poor version of scrollWheel: NSMenu happens to have implemented. MTTokenField is a mature alternative to pulling your hair out trying to stick a scroll view in an NSMenu.