An NSButton that repeats (after a delay) while holding the mouse down

DSFDelayedRepeatingButton.swift

//
//  DSFDelayedRepeatingButton.swift
//
//  Created by Darren Ford on 16/1/21.
//
// MIT License
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
//

#if canImport(AppKit) && os(macOS)

import AppKit

/// A simple NSButton that supports a delayed button repeat if the user clicks and holds the button
internal class DSFDelayedRepeatingButton: NSButton {

   private var eventTimer: Timer?

   deinit {
      self.eventTimer?.invalidate()
      self.eventTimer = nil
   }

   override func mouseDown(with _: NSEvent) {
      guard let w = self.window else {
         return
      }

      self.performClick(self)

      self.eventTimer = Timer.scheduledTimer(
         timeInterval: NSEvent.keyRepeatDelay,
         target: self,
         selector: #selector(self.initialTimerCallback),
         userInfo: "initial",
         repeats: false
      )

      RunLoop.current.add(self.eventTimer!, forMode: .eventTracking)

      var keepGoing = true
      while keepGoing {
         guard let theEvent = w.nextEvent(matching: [.leftMouseUp]) else {
            keepGoing = false
            break
         }

         switch theEvent.type {
         case .leftMouseUp:
            self.eventTimer?.invalidate()
            keepGoing = false
         default:
            break
         }
      }

      self.eventTimer?.invalidate()
      self.eventTimer = nil

      self.needsDisplay = true
   }

   @objc func initialTimerCallback(_ timer: Timer) {
      guard let which = timer.userInfo as? String else {
         return
      }

      if which == "initial" {
         // Remove the old timer first
         self.eventTimer?.invalidate()
         self.eventTimer = nil

         self.eventTimer = Timer.scheduledTimer(
            timeInterval: NSEvent.keyRepeatInterval,
            target: self,
            selector: #selector(self.initialTimerCallback),
            userInfo: "repeat",
            repeats: true
         )
         RunLoop.current.add(self.eventTimer!, forMode: .eventTracking)
      }

      self.sendAction(self.action, to: self.target)
   }
}

#endif