https://stackoverflow.com/questions/63043081/nstableview-selected-row-flickering-while-scrolling-with-arrow-keys

ViewController.swift

class ClipView: NSClipView {
    var isScrollAnimationEnabled: Bool = true
    
    override func scroll(to newOrigin: NSPoint) {
        if isScrollAnimationEnabled {
            super.scroll(to: newOrigin)
        } else {
            setBoundsOrigin(newOrigin)
        }
    }
}

class OutlineView: NSOutlineView {
    private var arrowKeysDown = Set<UInt16>()
    
    override func keyDown(with event: NSEvent) {
        if (125...126).contains(event.keyCode) {
            arrowKeysDown.insert(event.keyCode)
            (enclosingScrollView?.contentView as? ClipView)?.isScrollAnimationEnabled = false
        }
        super.keyDown(with: event)
    }
    
    override func keyUp(with event: NSEvent) {
        super.keyUp(with: event)
        arrowKeysDown.remove(event.keyCode)
        (enclosingScrollView?.contentView as? ClipView)?.isScrollAnimationEnabled = arrowKeysDown.isEmpty
    }
}

Did update the gist. We can set it to false explicitly in the keyDown, but we have to keep it in the keyUp to be sure that both Up / Down arrow keys are released.

@zrzka

I see, thanks. In practice I wasn't able to re-enable the scrolling animation with the scenario you described, as the down arrow keeps calling key down, which immediately disables it again. But it sure is best practice to not rely on that.

Yeah, you're probably right, feel free to modify it in any way :)