Issue with CGEventTapCreate() call.

Question

Hi All,

I'm trying to register for global key events using this code :

void function() {

CFMachPortRef keyUpEventTap = CGEventTapCreate(kCGHIDEventTap,kCGHeadInsertEventTap,kCGEventTapOptionListenOnly,CGEventMaskBit(kCGEventKeyUp),&keyUpCallback,NULL);

CFRunLoopSourceRef keyUpRunLoopSourceRef = CFMachPortCreateRunLoopSource(NULL, keyUpEventTap, 0);

CFRelease(keyUpEventTap);

CFRunLoopAddSource(CFRunLoopGetCurrent(), keyUpRunLoopSourceRef, kCFRunLoopDefaultMode);

CFRelease(keyUpRunLoopSourceRef);

}

The application crashes while executing CFMachPortCreateRunLoopSource() call. I think the crash is because of CGEventMaskBit(kCGEventKeyUp) when I create an event tap.

But if I create event tap using CGEventTapCreate(kCGHIDEventTap,kCGHeadInsertEventTap,kCGEventTapOptionListenOnly,CGEventMaskBit(kCGEventFlagsChanged),&keyUpCallback,NULL), the application works fine. It does not crash. I'm getting callbacks when any modifier key is pressed. But I need to get callbacks for delete key pressed.

Any ideas?

Thanks,

Dheeraj.

Answer 1

I think you need special permission to register for keyboard events. I forget off hand what that is, but to test it run the program as root and see if it still crashes.

Edit:

According to this article you must either run the program as root or enable assistive devices.

The crash may just be because CGEventTapCreate returns NULL.

Answer 2

I found the fix for this issue on this link :

http://www.cocoabuilder.com/archive/cocoa/242438-trouble-with-event-taps.html