How can I change the background color of a focused item of a NSTableView?

Here is a more simplified example of the app:

import SwiftUI

struct NSTableViewWrapper: NSViewRepresentable {

    class Coordinator: NSObject, NSTableViewDataSource, NSTableViewDelegate {
        var parent: NSTableViewWrapper

        init(parent: NSTableViewWrapper) {
            self.parent = parent
        }

        func numberOfRows(in tableView: NSTableView) -> Int { 1 }

        func tableView(_ tableView: NSTableView, viewFor tableColumn: NSTableColumn?, row: Int) -> NSView? {
            return NSTextField(labelWithString: "Item")
        }

        func tableView(_ tableView: NSTableView, rowActionsForRow row: Int, edge: NSTableView.RowActionEdge) -> [NSTableViewRowAction] {
            return [NSTableViewRowAction(style: .destructive, title: "Delete") { _, _ in }]
        }
    }

    func makeCoordinator() -> Coordinator {
        return Coordinator(parent: self)
    }

    func makeNSView(context: Context) -> NSScrollView {
        let scrollView = NSScrollView()
        let tableView = NSTableView()
    
        let column = NSTableColumn(identifier: NSUserInterfaceItemIdentifier("Column"))
        tableView.addTableColumn(column)

        tableView.delegate = context.coordinator
        tableView.dataSource = context.coordinator

        scrollView.documentView = tableView

        return scrollView
    }

    func updateNSView(_ nsView: NSScrollView, context: Context) {
        (nsView.documentView as? NSTableView)?.reloadData()
    }
}

struct ContentView: View {
    var body: some View {
        NSTableViewWrapper()
    }
}

And here is the demo:

There are two things which can be done:

1:

Add another tableView method into the Coordinator which looks like this:

func tableView(_ tableView: NSTableView, rowViewForRow row: Int) -> NSTableRowView? {
    return MyCustomRowView()
}

And MyCustomRowView would just have a isEmphasized property override:

class MyCustomRowView: NSTableRowView {
    override var isEmphasized: Bool {
        set {}
        get { false }
    }
}

It can not give us any selection color we want, but it does change the color. To gray:

2:

Replace property override with a method override in the MyCustomRowView from the code above:

class MyCustomRowView: NSTableRowView {
    override func drawSelection(in dirtyRect: NSRect) {
        NSColor.brown.setFill()
        self.bounds.fill()
    }
}

It changes the background, but not the background we had initially. It completely ignores the interaction with the swipe action:

Another thing that I could do – is change AccentColor in project's Assets.xcassets.

But it does not address the issue from this topic, because setting a color with 0.10% opacity gives an unexpected result :(

Here i set the same brown color, but set the slider at the very left (1%) in the Assets.xcassets making the color barely visible:

As you can see instead of giving me a barely brown color it gave me almost white...

Here is a solution i found:

1. Remove the highlight style of your tableView like this:

tableView.selectionHighlightStyle = .none

1. Set different background in  tableViewSelectionDidChange method like this:

func tableViewSelectionDidChange(_ notification: Notification) {
    guard let tableView = notification.object as? NSTableView else { return }
    
    guard tableView.selectedRow >= 0 else {
        for i in 0..<tableView.numberOfRows {
            guard let rowView = tableView.rowView(atRow: i, makeIfNecessary: false) else {
                return
            }
            rowView.backgroundColor = .clear
        }

        return
    }
    
    guard let rowView = tableView.rowView(atRow: tableView.selectedRow, makeIfNecessary: false) else {
        return
    }
    rowView.backgroundColor = .red.withAlphaComponent(0.1)
}

The full code can be found here.