NSOutlineView how to show blue outline during right click - cocoa

Question

Everyone discussed about how to get rid of the blue outline during right click... but me.
Instead, I'm trying to display the blue outline.
I didn't get any outline when I right clicked my outline view row. The menu appeared but the outline wasn't. You can see that the blue outline is not visible in this picture below:
Below is what I'm trying to achieve.
Update
This is how I implemented the NSMenu. I subclassed the NSOutlineView and made a new protocol to override NSOutlineViewDelegate.
This idea was to make it simple by letting the NSOutlineView ask the NSMenu for each item, so we can implement different menu for each item. It works but the blue outline view doesn't show up during right click.
KRMenuOutlineView.swift
import Cocoa
#objc protocol KRMenuOutlineViewDelegate: NSOutlineViewDelegate {
// This method will ask NSMenu for each item in outline view
func outlineView(_ outlineView: KRMenuOutlineView, menuFor item: Any, event: NSEvent) -> NSMenu?
}
class KRMenuOutlineView: NSOutlineView {
override var delegate: NSOutlineViewDelegate? {
didSet {
if let newValue = delegate {
/*
* Swift doesn't support overriding inherited properties with different type
* like Objective C Does, therefore we need internal delegate.
*/
internalDelegate = unsafeBitCast(newValue, to: KRMenuOutlineViewDelegate.self)
} else {
internalDelegate = nil
}
}
}
private var internalDelegate: KRMenuOutlineViewDelegate?
override func menu(for event: NSEvent) -> NSMenu? {
let point = self.convert(event.locationInWindow, from: nil)
if let item = self.item(atRow: self.row(at: point)) {
return self.internalDelegate?.outlineView(self, menuFor: item, event: event)
}
return super.menu(for: event)
}
}
Then, I use it in my view controller like this:
KRTreeViewController.swift
extension KRTreeViewController: KRMenuOutlineViewDelegate {
func outlineView(_ outlineView: KRMenuOutlineView, menuFor item: Any, event: NSEvent) -> NSMenu? {
let menu = NSMenu(title: "Contextual Menu")
menu.delegate = self
let key = String(utf16CodeUnits: [unichar(NSBackspaceCharacter)], count: 1) as String
let deleteMenuItem = menu.addItem(withTitle: "Delete",
action: #selector(didClickMenuItem(_:)),
keyEquivalent: key)
deleteMenuItem.representedObject = myItem
deleteMenuItem.target = self
return menu
}
#objc fileprivate func didClickMenuItem(_ menuItem: NSMenuItem) {
// ...
}
}

Answer 1

How to properly show a context menu:
If you have created your menu using a storyboard:
First, go to the storyboard and add the menu to the viewController that contains the outlineView.
Then make it an #IBOutlet so you can reference it later.
In a method like viewDidLoad(), add the menu to the outlineView by calling
outlineView.menu = myMenu
where myMenu can either be the one you created in Interface Builder or in code.
You can run the app now and should see the blue outline around the cell.
The problem now is that you don't know which cell the user has clicked.
To fix this, set yourself as the delegate of myMenu and adopt the NSMenuDelegate protocol.
func menuNeedsUpdate(_ menu: NSMenu) {
let row = self.outlineView.clickedRow
guard row != -1 else { return }
for item in menu.items {
item.representedObject = row
}
}
Here you can do whatever you need. This implementation sets the rowIndex as the representedObject of each menu item. Keep in mind that this only works on static outlineViews (ones that don't change in the background) and menus which only go one level deep.
You could also store the index or object represented by the cell (if the outlineView is not static) in a local variable.