swift - 你如何在 Swift 中使用 CGEventTapCreate？

Question

有没有人设法让这个函数在 Swift 中工作？

这是去年的引用 SO 帖子:Using CGEventTapCreate Trouble with parameters in Swift

Apple 文档:https://developer.apple.com/library/prerelease/mac/documentation/Carbon/Reference/QuartzEventServicesRef/index.html#//apple_ref/c/func/CGEventTapCreate

CGEventTapCallBack 的定义如下:

typealias CGEventTapCallBack = CFunctionPointer<((CGEventTapProxy, CGEventType, CGEvent!, UnsafeMutablePointer<Void>) -> Unmanaged<CGEvent>!)>

以下是我编写 block 的方式:

let eventTapCallBackBlock : @objc_block
(CGEventTapProxy, CGEventType, CGEventRef, UnsafeMutablePointer<Void>) -> CGEventRef =
{ (eventTapProxy: CGEventTapProxy, eventType: CGEventType, event: CGEventRef, refcon: UnsafeMutablePointer<Void>) in
  return event
}

然后我用像 unsafeBitCast(eventTapCallBackBlock, CGEventTapCallBack.self) 这样的回调参数调用了 CGEventTapCreate

我得到一个有效的 CFMachPortRef 返回，但在运行时我在第一个事件中得到一个访问冲突异常。在当前发布状态下，我“似乎”接近于 swift 的解决方案。

使用 Xcode 版本 6.4

Answer 1

CGEventTapCreate()的callback参数是一个C函数指针，在 Swift 1.x 中，无法使用 Swift 函数参数调用它。

但是，在 Swift 2 (Xcode 7) 中，接受函数指针参数的 C 函数可以使用闭包或全局函数调用(限制是闭包不得捕获其任何本地上下文)。

例如，这里是完整的翻译 Receiving, Filtering, and Modifying Key Presses and Releases swift :

import Foundation

func myCGEventCallback(proxy : CGEventTapProxy, type : CGEventType, event : CGEvent, refcon : UnsafeMutablePointer<Void>) -> Unmanaged<CGEvent>? {
    
    if [.KeyDown , .KeyUp].contains(type) {
        var keyCode = CGEventGetIntegerValueField(event, .KeyboardEventKeycode)
        if keyCode == 0 {
            keyCode = 6
        } else if keyCode == 6 {
            keyCode = 0
        }
        CGEventSetIntegerValueField(event, .KeyboardEventKeycode, keyCode)
    }
    return Unmanaged.passRetained(event)
}

let eventMask = (1 << CGEventType.KeyDown.rawValue) | (1 << CGEventType.KeyUp.rawValue)
guard let eventTap = CGEventTapCreate(.CGSessionEventTap,
    .HeadInsertEventTap,
    .Default,
    CGEventMask(eventMask),
    myCGEventCallback,
    nil) else {
        print("failed to create event tap")
        exit(1)
}

let runLoopSource = CFMachPortCreateRunLoopSource(kCFAllocatorDefault, eventTap, 0)
CFRunLoopAddSource(CFRunLoopGetCurrent(), runLoopSource, kCFRunLoopCommonModes)
CGEventTapEnable(eventTap, true)
CFRunLoopRun()

---

Swift 3 的更新:

import Foundation

func myCGEventCallback(proxy: CGEventTapProxy, type: CGEventType, event: CGEvent, refcon: UnsafeMutableRawPointer?) -> Unmanaged<CGEvent>? {
    
    if [.keyDown , .keyUp].contains(type) {
        var keyCode = event.getIntegerValueField(.keyboardEventKeycode)
        if keyCode == 0 {
            keyCode = 6
        } else if keyCode == 6 {
            keyCode = 0
        }
        event.setIntegerValueField(.keyboardEventKeycode, value: keyCode)
    }
    return Unmanaged.passRetained(event)
}

let eventMask = (1 << CGEventType.keyDown.rawValue) | (1 << CGEventType.keyUp.rawValue)
guard let eventTap = CGEvent.tapCreate(tap: .cgSessionEventTap,
                                      place: .headInsertEventTap,
                                      options: .defaultTap,
                                      eventsOfInterest: CGEventMask(eventMask),
                                      callback: myCGEventCallback,
                                      userInfo: nil) else {
                                        print("failed to create event tap")
                                        exit(1)
}

let runLoopSource = CFMachPortCreateRunLoopSource(kCFAllocatorDefault, eventTap, 0)
CFRunLoopAddSource(CFRunLoopGetCurrent(), runLoopSource, .commonModes)
CGEvent.tapEnable(tap: eventTap, enable: true)
CFRunLoopRun()