How to show context menu in NSCollectionView

Issue #321

Detect locationInWindow in NSEvent

class ClickedCollectionView: NSCollectionView {
    var clickedIndex: Int?

    override func menu(for event: NSEvent) -> NSMenu? {
        clickedIndex = nil

        let point = convert(event.locationInWindow, from: nil)
        for index in 0..<numberOfItems(inSection: 0) {
            let frame = frameForItem(at: index)
            if NSMouseInRect(point, frame, isFlipped) {
                clickedIndex = index
                break
            }
        }

        return super.menu(for: event)
    }
}

let menu = NSMenu()
menu.addItem(NSMenuItem(title: "Delete", action: #selector(didSelectDelete(_:)), keyEquivalent: ""))
collectionView.menu = menu

@objc func didSelectDelete(_ item: NSMenuItem) {
    guard
        let index = collectionView.clickedIndex,
        index < notes.count
    else {
        return
    }
    
    let indexPath = IndexPath(item: index, section: 0)
    notes.remove(at: index)
    collectionView.deleteItems(at: Set(arrayLiteral: indexPath))
}

For NSCollectionView with more than 1 sections

let frame = layoutAttributesForItem(at: IndexPath(item: index, section: 0))?.frame ?? .zero

Use Omnia

Omnia supports clicked indexPath for multi section NSCollectionView

collectionViewHandler.addMenuItem(title: "Add to Favorite", action: { item in
    print(item)            
})