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static OSStatus applicationEventHandler(EventHandlerCallRef next_ref, EventRef event, void *data);
static EventHandlerUPP applicationEventHandlerUPP = 0;
static EventTypeSpec application_events[] = {
    { kEventClassAccessibility,  kEventAccessibleGetChildAtPoint },
    { kEventClassAccessibility,  kEventAccessibleGetNamedAttribute }
};

static CFStringRef kObjectQtAccessibility = CFSTR("com.trolltech.qt.accessibility");
static EventHandlerUPP objectCreateEventHandlerUPP = 0;
static EventTypeSpec objectCreateEvents[] = {
    { kEventClassHIObject,  kEventHIObjectConstruct },
    { kEventClassHIObject,  kEventHIObjectInitialize },
    { kEventClassHIObject,  kEventHIObjectDestruct },
    { kEventClassHIObject,  kEventHIObjectPrintDebugInfo }
};

static OSStatus accessibilityEventHandler(EventHandlerCallRef next_ref, EventRef event, void *data);
static EventHandlerUPP accessibilityEventHandlerUPP = 0;
static EventTypeSpec accessibilityEvents[] = {
    { kEventClassAccessibility,  kEventAccessibleGetChildAtPoint },
    { kEventClassAccessibility,  kEventAccessibleGetFocusedChild },
    { kEventClassAccessibility,  kEventAccessibleGetAllAttributeNames },
    { kEventClassAccessibility,  kEventAccessibleGetNamedAttribute },
    { kEventClassAccessibility,  kEventAccessibleSetNamedAttribute },
    { kEventClassAccessibility,  kEventAccessibleIsNamedAttributeSettable },
    { kEventClassAccessibility,  kEventAccessibleGetAllActionNames },
    { kEventClassAccessibility,  kEventAccessiblePerformNamedAction },
    { kEventClassAccessibility,  kEventAccessibleGetNamedActionDescription }
};

static void installAcessibilityEventHandler(HIObjectRef hiObject)
{
    if (!accessibilityEventHandlerUPP)
        accessibilityEventHandlerUPP = NewEventHandlerUPP(accessibilityEventHandler);

    InstallHIObjectEventHandler(hiObject, accessibilityEventHandlerUPP,
                                        GetEventTypeCount(accessibilityEvents),
                                        accessibilityEvents, 0, 0);
}

static OSStatus objectCreateEventHandler(EventHandlerCallRef next_ref, EventRef event, void *data)
{
    Q_UNUSED(data)
    Q_UNUSED(event)
    Q_UNUSED(next_ref)
    return noErr;
}

static void registerQtAccessibilityHIObjectSubclass()
{
    if (!objectCreateEventHandlerUPP)
        objectCreateEventHandlerUPP = NewEventHandlerUPP(objectCreateEventHandler);
    OSStatus err = HIObjectRegisterSubclass(kObjectQtAccessibility, 0, 0, objectCreateEventHandlerUPP,
                                         GetEventTypeCount(objectCreateEvents), objectCreateEvents, 0, 0);
    if (err && err != hiObjectClassExistsErr)
        qWarning("qaccessible_mac internal error: Could not register accessibility HIObject subclass");
}

static void installApplicationEventhandler()
{
    if (!applicationEventHandlerUPP)
        applicationEventHandlerUPP = NewEventHandlerUPP(applicationEventHandler);

    OSStatus err = InstallApplicationEventHandler(applicationEventHandlerUPP,
                            GetEventTypeCount(application_events), application_events,
                            0, 0);

    if (err && err != eventHandlerAlreadyInstalledErr)
        qWarning("qaccessible_mac internal error: Could not install application accessibility event handler");
}

static void removeEventhandler(EventHandlerUPP eventHandler)
{
    if (eventHandler) {
        DisposeEventHandlerUPP(eventHandler);
        eventHandler = 0;
    }
}