tap.swift

//
//  ScreenCapture.swift
//  Screenotate
//
//  Created by Omar Rizwan on 7/6/17.
//  Copyright © 2017 Omar Rizwan. All rights reserved.
//

import Foundation
import Cocoa

class Tap {
    var eventTap: CFMachPort!
    var selfPtr: Unmanaged<Tap>!

    init() {
        // Catch all events.
        let eventMask: CGEventMask = ~0
        
        // Need to keep this pointer around for a while until we're sure of being done,
        // or else Tap gets freed and the event tap has a dangling pointer to it (??)
        selfPtr = Unmanaged.passRetained(self)

        eventTap = CGEvent.tapCreate(
            tap: CGEventTapLocation.cgSessionEventTap,
            place: CGEventTapPlacement.headInsertEventTap,
            options: CGEventTapOptions.defaultTap,
            eventsOfInterest: eventMask,
            callback: { proxy, type, event, refcon in
                // Trick from https://stackoverflow.com/questions/33260808/how-to-use-instance-method-as-callback-for-function-which-takes-only-func-or-lit
                let mySelf = Unmanaged<Tap>.fromOpaque(refcon!).takeUnretainedValue()
                return mySelf.eventTapCallback(proxy: proxy, type: type, event: event, refcon: refcon)
            },
            userInfo: selfPtr.toOpaque())!

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

    func eventTapCallback(proxy: CGEventTapProxy, type: CGEventType, event: CGEvent, refcon: UnsafeMutableRawPointer?) -> Unmanaged<CGEvent>? {
        if type == CGEventType.tapDisabledByUserInput {
            return nil
        }

        // Need to convert CGEvent to NSEvent to analyze
        // Touch Bar events for some reason.
        if #available(OSX 10.12.2, *) {
            if let cocoaEvent = NSEvent(cgEvent: event) {
                if cocoaEvent.type == NSEvent.EventType.directTouch {
                    print("Touch bar touch")
                }
            }
        }

        switch type {
        case .leftMouseDown:
            print("Left mouse down")
            break
        case .keyDown:
            print("Key down", event.getIntegerValueField(.keyboardEventKeycode))
            break
        default:
            break
        }

        // print("event", type, type.rawValue, event)

        // If you don't return the event, it will be suppressed!
        return Unmanaged.passUnretained(event)
    }

    func done() {
        CGEvent.tapEnable(tap: self.eventTap, enable: false)

        // FIXME: Wait some random period of time and then manually free the
        // event tap pointer?
        // This whole thing is really weird and probably overthinking --
        // stems from the odd unused construction of the Tap object at main.
        DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
            let _ = self.selfPtr.autorelease()
        }
    }
}

// Ripped off from https://stackoverflow.com/questions/40144259/modify-accessibility-settings-on-macos-with-swift
// You need accessibility access to tap key events.
public func checkAccess() -> Bool{
    //get the value for accesibility
    let checkOptPrompt = kAXTrustedCheckOptionPrompt.takeUnretainedValue() as NSString
    //set the options: false means it wont ask
    //true means it will popup and ask
    let options = [checkOptPrompt: true]
    //translate into boolean value
    let accessEnabled = AXIsProcessTrustedWithOptions(options as CFDictionary?)
    return accessEnabled
}
if checkAccess() {
    // Eh. This is not good OOP
    Tap()
} else {
    print("Enable access in System Preferences, then rerun.")
}

it doesnt leak