Strange CGEventPost mouse click behavior

In my Mac application I am trying to intercept right mouse down/up events using CG Event Taps. I have the code that is registering as a listener working just fine. What I am trying to do is intercept when the user clicks down with the right mouse button, and eat the event temporarily. When they let go of the right mouse button I want to post a right mouse down event if they haven't moved the mouse since the original mouse down event. If they have moved the mouse I want my app's code to do something different. This all works great if I run the code on my Macbook using the trackpad. However, when I plug a mouse into the same computer every other mouse down event does not trigger my callback.

The basic logic for doing this is I keep track of an "ignore next event" bool. When my program first runs this is set to false. When I get a right mouse down event I return NULL. When the right mouse up event triggers I create and post a new right mouse down event with ignoreNext to true. I then return the right mouse up event.

Here is my code:

CGPoint mouseDownPoint;
bool ignoreNext;

//---------------------------------------------------------------------------
CGEventRef MouseTapCallback( CGEventTapProxy aP开发者_运维问答roxy, CGEventType aType, CGEventRef aEvent, void* aRefcon ) 
//---------------------------------------------------------------------------
{
    if( aType == kCGEventRightMouseDown ) NSLog( @"down" );
    else if( aType == kCGEventRightMouseUp ) NSLog( @"up" );
    else NSLog( @"other" );

    NSLog( @"ignored: %d", ignoreNext );

    CGPoint theLocation = CGEventGetLocation(aEvent);

    if( !ignoreNext )
    {
        if( aType == kCGEventRightMouseDown )
        {
            mouseDownPoint = theLocation;

            return NULL;
        }
        else if( aType == kCGEventRightMouseUp )
        {
            if( abs( theLocation.x - mouseDownPoint.x ) < 1 &&
                abs( theLocation.y - mouseDownPoint.y ) < 1 )
            {
                ignoreNext = true;

                CGEventRef theNewEvent = CGEventCreateMouseEvent( NULL,
                                                                 kCGEventRightMouseDown, 
                                                                 mouseDownPoint, 
                                                                 kCGMouseButtonRight );

                CGEventSetType( theNewEvent, kCGEventRightMouseDown );
                CGEventPost( kCGHIDEventTap, theNewEvent );

                return aEvent;
            }
            else
            {
                // execute my app's code here...

                return NULL;
            }
        }
    }

    ignoreNext = false;
    return aEvent; 
}

The output for this when I test it with the track pad is (working correctly):

down ignored: 0 up ignored: 0 down ignored: 1

The output for this when I test it with an actual mouse (note: the mouse down event is missing on the second run through):

First time clicking down then up...

down ignored: 0 up ignored: 0 down ignored: 1

Second time, the mouse down event doesn't trigger my callback...

up ignored: 0

Has anyone seen anything like this before, and if so, what did you do to solve this problem? Thanks for your time.