How to tap (hook) F7 through F12 and Power/Eject o

This question follows from How to hook/remap an arbitrary keyboard event on OSX?

So far I am able to tap the modifier keys and most of the other keys using:

    _eventTap = CGEventTapCreate( kCGHIDEventTap, 
                                  kCGHeadInsertEventTap,
                                  kCGEventTapOptionDefault,
                                       CGEventMaskBit( kCGEventKeyDown )
                                     | CGEventMaskBit( kCGEventFlagsChanged )
                                     ,
                                  (CGEventTapCallBack)_tapCallback,
                                  (__bridge void *)(self));

Notably, F3 correctly reports a keycode (160) before taking action. i.e. I can disable the action by having my event handler return NULL (and thus failing to propagate the event).

However, F7 through F12 and Eject/Power don't trigger the callback.

If I add:

                                     | CGEventMaskBit( NSSystemDefined )

... Now the remaining Fx keys DO trigger the callback (although Power/Eject still doesn't), but I can't access the keyCode method of the event.

It produces an error:

2015-05-21 12:30:02.044 tap_k[16532:698660] NSSystemDefined: 0 2015-05-21 12:30:02.044 tap_k[16532:698660] * Assertion failure in -[NSEvent keyCode], /SourceCache/AppKit/AppKit-1347.57/AppKit.subproj/NSEvent.m:2471 2015-05-21 12:30:02.045 tap_k[16532:698660] * Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Invalid message sent to event "NSEvent: type=SysDefined loc=(882,687) time=118943.3 flags=0 win=0x0 winNum=0 ctxt=0x0 subtype=8 data1=2560 data2=-1"'

So either:
(1) I need some other way of extracting some unique identifier from NSEvent, or
(2) I need to tap/hook at a lower level.

Working with (1), I notice NSEvent has a data1 property. Logging this is in hex gives:

2015-05-21 12:40:05.428 tap_k[16576:704298] NSSystemDefined: 140b00
2015-05-21 12:40:06.914 tap_k[16576:704298] NSSystemDefined: 100a00
2015-05-21 12:40:06.992 tap_k[16576:704298] NSSystemDefined: 100b00
2015-05-21 12:40:07.600 tap_k[16576:704298] NSSystemDefined: 130a00
2015-05-21 12:40:07.690 tap_k[16576:704298] NSSystemDefined: 130b00
2015-05-21 12:40:08.219 tap_k[16576:704298] NSSystemDefined: 70a00
2015-05-21 12:40:08.277 tap_k[16576:704298] NSSystemDefined: 70b00
2015-05-21 12:40:09.062 tap_k[16576:704298] NSSystemDefined: 10a00
2015-05-21 12:40:09.186 tap_k[16576:704298] NSSystemDefined: 10b00
2015-05-21 12:40:09.637 tap_k[16576:704298] NSSystemDefined: a00
2015-05-21 12:40:09.726 tap_k[16576:704298] NSSystemDefined: b00

.. When I keydown/keyup F6 F7 F8 F9 F10 F11 F12.

(also, the last value changes to a 1 for repeats).

So I guess I could just eat events with these values, and pass other NSSystemDefined events through.

And it still doesn't solve the problem of catching Eject/Power.

But is there a cleaner/better way?

If anyone is interested to play around, here is the complete code:

// compile and run from the commandline with:
//    clang -fobjc-arc -framework Cocoa  ./foo.m  -o foo
//    sudo ./foo

#import <Foundation/Foundation.h>
#import <AppKit/NSEvent.h>

typedef CFMachPortRef EventTap;

// - - - - - - - - - - - - - - - - - - - - -

@interface KeyChanger : NSObject
{
@private
    EventTap            _eventTap;
    CFRunLoopSourceRef  _runLoopSource;
    CGEventRef          _lastEvent;
}
@end

// - - - - - - - - - - - - - - - - - - - - -

CGEventRef _tapCallback(
                        CGEventTapProxy proxy,
                        CGEventType     type,
                        CGEventRef      event,
                        KeyChanger*     listener
                        );

// - - - - - - - - - - - - - - - - - - - - -

@implementation KeyChanger

- (BOOL)tapEvents
{
    if (!_eventTap) {
        NSLog(@"Initializing an event tap.");

        // kCGHeadInsertEventTap -- new event tap should be inserted before any pre-existing event taps at the same location,
        _eventTap = CGEventTapCreate( kCGHIDEventTap, // kCGSessionEventTap,
                                      kCGHeadInsertEventTap,
                                      kCGEventTapOptionDefault,
                                           CGEventMaskBit( kCGEventKeyDown )
                                         | CGEventMaskBit( kCGEventFlagsChanged )
                                         | CGEventMaskBit( NSSystemDefined )
                                         ,
                                      (CGEventTapCallBack)_tapCallback,
                                      (__bridge void *)(self));
        if (!_eventTap) {
            NSLog(@"unable to create event tap. must run as root or "
                    "add privlidges for assistive devices to this app.");
            return NO;
        }
    }
    CGEventTapEnable(_eventTap, TRUE);

    return [self isTapActive];
}

- (BOOL)isTapActive
{
    return CGEventTapIsEnabled(_eventTap);
}

- (void)listen
{
    if( ! _runLoopSource ) {
        if( _eventTap ) { //dont use [self tapActive]
            _runLoopSource = CFMachPortCreateRunLoopSource( kCFAllocatorDefault,
                                                            _eventTap, 0);
            // Add to the current run loop.
            CFRunLoopAddSource( CFRunLoopGetCurrent(), _runLoopSource,
                                kCFRunLoopCommonModes);

            NSLog(@"Registering event tap as run loop source.");
            CFRunLoopRun();
        }else{
            NSLog(@"No Event tap in place! You will need to call "
                    "listen after tapEvents to get events.");
        }
    }
}

- (CGEventRef)processEvent:(CGEventRef)cgEvent
{
    NSEvent* event = [NSEvent eventWithCGEvent:cgEvent];

    NSUInteger modifiers = [event modifierFlags] &
        (NSCommandKeyMask | NSAlternateKeyMask | NSShiftKeyMask | NSControlKeyMask);

    enum {
       kVK_ANSI_3 = 0x14,
    };


    switch( event.type ) {
        case NSFlagsChanged:
            NSLog(@"NSFlagsChanged: %d", event.keyCode);
            break;

        case NSSystemDefined:
            NSLog(@"NSSystemDefined: %x", event.data1);
            return NULL;

        case kCGEventKeyDown:
            NSLog(@"KeyDown: %d", event.keyCode);
            break;

        default:
            NSLog(@"WTF");
    }


    // TODO: add other cases and do proper handling of case
    if (
        //[event.characters caseInsensitiveCompare:@"3"] == NSOrderedSame
        event.keyCode == kVK_ANSI_3
        && modifiers == NSShiftKeyMask
        ) 
    {
        NSLog(@"Got SHIFT+3");

        event = [NSEvent keyEventWithType: event.type
                                 location: NSZeroPoint
                            modifierFlags: event.modifierFlags & ! NSShiftKeyMask
                                timestamp: event.timestamp
                             windowNumber: event.windowNumber
                                  context: event.context
                               characters: @"#"
              charactersIgnoringModifiers: @"#"
                                isARepeat: event.isARepeat
                                  keyCode: event.keyCode];
    }
    _lastEvent = [event CGEvent];
    CFRetain(_lastEvent); // must retain the event. will be released by the system
    return _lastEvent;
}

- (void)dealloc
{
    if( _runLoopSource ) {
        CFRunLoopRemoveSource( CFRunLoopGetCurrent(), _runLoopSource, kCFRunLoopCommonModes );
        CFRelease( _runLoopSource );
    }
    if( _eventTap ) {
        //kill the event tap
        CGEventTapEnable( _eventTap, FALSE );
        CFRelease( _eventTap );
    }
}

@end

// - - - - - - - - - - - - - - - - - - - - -

CGEventRef _tapCallback(
                        CGEventTapProxy proxy,
                        CGEventType     type,
                        CGEventRef      event,
                        KeyChanger*     listener
                        )
{
    //Do not make the NSEvent here.
    //NSEvent will throw an exception if we try to make an event from the tap timout type
    @autoreleasepool {
        if( type == kCGEventTapDisabledByTimeout ) {
            NSLog(@"event tap has timed out, re-enabling tap");
            [listener tapEvents];
            return nil;
        }
        if( type != kCGEventTapDisabledByUserInput ) {
            return [listener processEvent:event];
        }
    }
    return event;
}

// - - - - - - - - - - - - - - - - - - - - -

int main(int argc, const char * argv[])
{
    @autoreleasepool {
        KeyChanger* keyChanger = [KeyChanger new];
        [keyChanger tapEvents];
        [keyChanger listen];//blocking call.
    }
    return 0;
}

回答1:

I'd just point out that if you haven't, you should look into MASShortcut to see how it hooks in for the F7-F12 keys. That said, I don't believe it can recognize the Power + Eject keys.

回答2:

This goes halfway. It prints out the scancode for every key. It could really do with being rewritten in ObjC/ARC to tidy up the retain/release bobbins.

Does anyone feel like having a go?

I've pulled the code from Using IOHIDManager to Get Modifier Key Events

// compile and run from the commandline with:
//    clang  -framework coreFoundation  -framework IOKit  ./HID.c  -o hid
//    sudo ./hid

// This code works with the IOHID library to get notified of keys.
//   Still haven't figured out how to truly intercept with
//   substitution.

#include <IOKit/hid/IOHIDValue.h>
#include <IOKit/hid/IOHIDManager.h>

void myHIDKeyboardCallback( void* context,  IOReturn result,  void* sender,  IOHIDValueRef value )
{
    IOHIDElementRef elem = IOHIDValueGetElement( value );

    if (IOHIDElementGetUsagePage(elem) != 0x07)
        return;

    uint32_t scancode = IOHIDElementGetUsage( elem );

    if (scancode < 4 || scancode > 231)
        return;

    long pressed = IOHIDValueGetIntegerValue( value );

    printf( "scancode: %d, pressed: %ld\n", scancode, pressed );
}


CFMutableDictionaryRef myCreateDeviceMatchingDictionary( UInt32 usagePage,  UInt32 usage )
{
    CFMutableDictionaryRef dict = CFDictionaryCreateMutable(
                                                            kCFAllocatorDefault, 0
                                                        , & kCFTypeDictionaryKeyCallBacks
                                                        , & kCFTypeDictionaryValueCallBacks );
    if ( ! dict )
        return NULL;

    CFNumberRef pageNumberRef = CFNumberCreate( kCFAllocatorDefault, kCFNumberIntType, & usagePage );
    if ( ! pageNumberRef ) {
        CFRelease( dict );
        return NULL;
    }

    CFDictionarySetValue( dict, CFSTR(kIOHIDDeviceUsagePageKey), pageNumberRef );
    CFRelease( pageNumberRef );

    CFNumberRef usageNumberRef = CFNumberCreate( kCFAllocatorDefault, kCFNumberIntType, & usage );

    if ( ! usageNumberRef ) {
        CFRelease( dict );
        return NULL;
    }

    CFDictionarySetValue( dict, CFSTR(kIOHIDDeviceUsageKey), usageNumberRef );
    CFRelease( usageNumberRef );

    return dict;
}


int main(void)
{
    IOHIDManagerRef hidManager = IOHIDManagerCreate( kCFAllocatorDefault, kIOHIDOptionsTypeNone );

    CFArrayRef matches;
    {
        CFMutableDictionaryRef keyboard = myCreateDeviceMatchingDictionary( 0x01, 6 );
        CFMutableDictionaryRef keypad   = myCreateDeviceMatchingDictionary( 0x01, 7 );

        CFMutableDictionaryRef matchesList[] = { keyboard, keypad };

        matches = CFArrayCreate( kCFAllocatorDefault, (const void **)matchesList, 2, NULL );
    }

    IOHIDManagerSetDeviceMatchingMultiple( hidManager, matches );

    IOHIDManagerRegisterInputValueCallback( hidManager, myHIDKeyboardCallback, NULL );

    IOHIDManagerScheduleWithRunLoop( hidManager, CFRunLoopGetMain(), kCFRunLoopDefaultMode );

    IOHIDManagerOpen( hidManager, kIOHIDOptionsTypeNone );

    CFRunLoopRun(); // spins
}