A convenience type for working with the CFDictionary values returned by CGWindowListCopyWindowInfo(_:, _:)

CGWindowDictionary.swift

//
//  CGWindowDictionary.swift
//
//  Created by Stephan Casas on 11/2/23.
//

import Foundation
import CoreGraphics
import AppKit

typealias CGWindowDictionary = [CFString: Any]

// MARK: - Utilities

/// A convenience type for working with the CFDictionary values returned by `CGWindowListCopyWindowInfo(_:, _:)`.
extension CGWindowDictionary {

  /// Get a list of modernized window representations as `[CGWindowDictionary]` using
  /// the given constraints.
  /// - Parameters:
  ///   - option: The native window list filter option.
  ///   - window: The relative window when considering ordered window list filters.
  /// - Returns: An array of `CGWindowDictionary` types which match the given parameters.
  static func list(
    matching option: CGWindowListOption = .optionAll,
    relativeTo window: CGWindowID = kCGNullWindowID,
    where isIncluded: ((CGWindowDictionary) -> Bool)? = nil
  ) -> [CGWindowDictionary] {
    let windowList = CGWindowListCopyWindowInfo(
      option, window
    ) as? [CGWindowDictionary] ?? []

    guard let isIncluded = isIncluded else {
      return windowList
    }

    return windowList.filter(isIncluded)
  }

  /// Get the frontmost window dictionary for the window which is both on-screen and the
  /// frontmost window owned by the given process identifier.
  /// - Parameter owner: The window-owning process for which the frontmost window should be resolved.
  /// - Returns: The dictionary representation of the frontmost window of the given process.
  static func frontmost(for owner: pid_t) -> CGWindowDictionary? {
    var windowList = CGWindowDictionary.list(
      matching: .optionOnScreenOnly,
      where: { $0.processIdentifier == owner })

    var frontmost = windowList.first
    while windowList.count > 1 {
      guard let _frontmost = windowList.first else {
        return frontmost
      }

      frontmost = _frontmost

      windowList = CGWindowDictionary.list(
        matching: .optionOnScreenAboveWindow,
        relativeTo: _frontmost.id,
        where: { $0.processIdentifier == owner })
    }

    return frontmost
  }

  static func frontmost(for bundleIdentifier: String) -> CGWindowDictionary? {
    guard let processIdentifier = NSRunningApplication.runningApplications(
      withBundleIdentifier: bundleIdentifier
    ).first?.processIdentifier else {
      return nil
    }

    return .frontmost(for: processIdentifier)
  }


}

// MARK: - Typecast Properties

extension CGWindowDictionary {

  /// The window server-tracked window ID for this window.
  var id: CGWindowID {
    self[kCGWindowNumber] as! CGWindowID
  }

  /// The process name for the process which owns this window.
  var processName: String {
    self[kCGWindowOwnerName] as! String
  }

  /// The process identifier for the process which owns this window.
  var processIdentifier: pid_t {
    self[kCGWindowOwnerPID] as! pid_t
  }

  /// The title of this window.
  var name: String {
    (self[kCGWindowName] as? String) ?? ""
  }

  /// The window's bounds in the Quartz/CoreGraphics coordinate space — where `(0, 0)` is at the leftmost-lowermost point of the display which owns the space with the lowest ordered index value.
  var bounds: CGRect {
    .init(dictionaryRepresentation: self[kCGWindowBounds] as! CFDictionary)!
  }

  /// The layer at which this window draws.
  var layer: Int32 {
    self[kCGWindowLayer] as! Int32
  }

  /// The window's bounds in the AppKit coordinate space — where `(0, 0)` is at the leftmost-uppermost point of the display which owns the space with the lowest ordered index value.
  var appKitBounds: CGRect {
    guard
      let NSCGSWindow = objc_getClass(
        "NSCGSWindow") as? AnyClass,
      let convertRectFromCGCoordinatesPtr = class_getClassMethod(
        NSCGSWindow, Selector(("convertRectFromCGCoordinates:")))
    else { fatalError(
      "Could not load private class method +[NSCGSWindow convertRectFromCGCoordinates:]."
    ) }

    return unsafeBitCast(
      method_getImplementation(convertRectFromCGCoordinatesPtr),
      to: (@convention(c) (CGRect) -> CGRect).self
    )(self.bounds)
  }

  /// The `AXUIElement` (`AXApplication`) application element representing the owner process of this window.
  var axApplication: AXUIElement? {
    AXUIElementCreateApplication(self.processIdentifier)
  }

  /// The *most likely* `AXUIElement` representation of this window.
  ///
  /// There is no *documented* canonical associative value linking `NSWindow` to its `AXUIElement` representation.
  /// This extension attempts a best guess based solely on the bounds of the window. Matching further on the window name may, in
  /// some cases, reduce the likelihood of collisions but may also contribute to a greater number of false negatives.
  var axElement: AXUIElement? {
    guard let axApp = self.axApplication else {
      return nil
    }

    let bounds = self.bounds

    var windowList: AnyObject?
    guard AXUIElementCopyAttributeValue(
      axApp, kAXWindowsAttribute as CFString, &windowList
    ) == .success else {
      return nil
    }

    return (windowList as? [AXUIElement])?.first(where: { windowElement in
      var positionValue: AnyObject?
      var sizeValue: AnyObject?
      guard
        AXUIElementCopyAttributeValue(
          windowElement, kAXPositionAttribute as CFString, &positionValue) == .success,
        AXUIElementCopyAttributeValue(
          windowElement, kAXSizeAttribute as CFString, &sizeValue) == .success
      else {
        return false
      }
      var position = CGPointZero
      var size = CGSizeZero
      guard
        AXValueGetValue(positionValue as! AXValue, .cgPoint, &position),
        AXValueGetValue(sizeValue as! AXValue, .cgSize, &size)
      else {
        return false
      }

      return bounds.equalTo(.init(origin: position, size: size))
    })
  }

  /// The bundle identifier for the owner process of this window.
  var bundleId: String? {
    NSRunningApplication(
      processIdentifier: self.processIdentifier
    )?.bundleIdentifier
  }

}