Event Tap(CFMachPortRef) problem for Hot Key- callback is not invoked

Question

I am developing a desktop application that supports one of the feature through Hot Key. I am using Event Tap for this to work.

But, sometimes (randomly) the callback is not invoked; Hot Key does not work and hence the feature seems to be not working.

How can I identify the problem here?

Following is the code snippet:

-( void )startEventTapinThread //Called in a separate thread.
{
    NSAutoreleasePool *pool =[ [ NSAutoreleasePool alloc] init];
    
    CFRunLoopRef runloop =(CFRunLoopRef)CFRunLoopGetCurrent();
    CGEventMask interestedEvents = CGEventMaskBit(kCGEventFlagsChanged)|CGEventMaskBit(kCGEventKeyDown);
    CFMachPortRef eventTap = CGEventTapCreate(kCGSessionEventTap, kCGHeadInsertEventTap, 0, interestedEvents, myCGEventCallback, self); //self is the object pointer our method
    CFRunLoopSourceRef source = CFMachPortCreateRunLoopSource(kCFAllocatorDefault, eventTap, 0);
    CFRunLoopAddSource((CFRunLoopRef)runloop , source, kCFRunLoopCommonModes);
    CFRunLoopRun();
    [ pool release];
}

CGEventRef myCGEventCallback(CGEventTapProxy proxy, CGEventType type, CGEventRef event, void *refcon)
{
    CGEventType eventType = CGEventGetType(event);
    //execute the code related to feature
}

After debugging for hours I noticed that myCGEventCallback is invoked only for kCGEventFlagsChanged ; It is not invoked only for kCGEventKeyDown. What am I doing wrong? — spd, Mar 28 '11 at 06:21

score 1 · Answer 1 · answered Sep 13 '11 at 08:15

I would pass the event kCGEventMaskForAllEvents rather than only set the hook for certain events.

Then, in your callback function, filter the events.

CGEventRef myCGEventCallback(CGEventTapProxy proxy, CGEventType type, CGEventRef event, void *refcon)
{

if (type == kCGEventTapDisabledByTimeout) {
    NSLog(@"Event Taps Disabled! Re-enabling");
    CGEventTapEnable(eventTap, true);
    return event;
}

if (type == kCGEventLeftMouseDown) {
    //...
}

if (type != kCGEventKeyDown) {
    //...
}

if (type == kCGEventKeyDown) {
    //...
}

Let me try this and post the output here :) – spd Sep 14 '11 at 03:39 — spd, Sep 14 '11 at 03:39

score 0 · Answer 2 · edited May 23 '17 at 11:49

0

The solution to your problem is most likely described in the top answer to this question. I would mark this question as a dupe if I had the rep score to do so.

edited May 23 '17 at 11:49

Community

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1

answered Mar 08 '14 at 18:50

Winter Dragoness

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Event Tap(CFMachPortRef) problem for Hot Key- callback is not invoked

2 Answers2