How to properly connect NSColorPanel to a server to avoid overload

Question

I'm using NSColorPanel to change the color of a view. The color of this view is also saved in a database (Firestore).

import AppKit

class ColorPanel {

    static var shared = ColorPanel()

    private var stage: DB.Stage.Document? = nil

    private let cp = NSColorPanel.shared

    init() {
        cp.setTarget(self)
        cp.setAction(#selector(colorDidChange(sender:)))
        cp.isContinuous = false
    }

    func show(stage: DB.Stage.Document) {
        self.stage = stage
        cp.makeKeyAndOrderFront(nil)
    }

    @objc func colorDidChange(sender: NSColorPanel) {
        guard let stage = stage else { return }
        stage.data?.color.red = Double(sender.color.redComponent)
        stage.data?.color.green = Double(sender.color.greenComponent)
        stage.data?.color.blue = Double(sender.color.blueComponent)
        stage.update()
    }
}

The problem is that I would like to set isContinuos true in order to see my view changing color real-time, but is sending too much updates to the server, so I have been forced to set it false.

There is a way to solve this? I just need to do an update when I finish the drag but I don't know how.

p.s. To call the ColorPanel in my SwiftUI view I do:

ColorPanel.shared.show(stage: stage)

Answer 1

Please try an approach I would use. Disclaimer: not tested due to absent Firestore setup

import Combine

class ColorPanel {

    static var shared = ColorPanel()

    private var stage: DB.Stage.Document? = nil

    private let cp = NSColorPanel.shared

    private var subscriber: AnyCancellable?
    private let publisher =
        PassthroughSubject<NSColor, Never>()
            .throttle(for: 10, scheduler: RunLoop.main, latest: true)

    init() {
        cp.setTarget(self)
        cp.setAction(#selector(colorDidChange(sender:)))
        cp.isContinuous = true
    }

    func show(stage: DB.Stage.Document) {
        self.stage = stage
        self.subscriber = nil

        if stage != nil {
            self.subscriber = self.publisher
                .sink { _ in
                    self.stage.update() // << be called once per 10 seconds
                }
        }
        cp.makeKeyAndOrderFront(nil)
    }

    @objc func colorDidChange(sender: NSColorPanel) {
        guard let stage = stage else { return }
        stage.data?.color.red = Double(sender.color.redComponent)
        stage.data?.color.green = Double(sender.color.greenComponent)
        stage.data?.color.blue = Double(sender.color.blueComponent)

        self.publisher.upstream.send(sender.color)
    }
}