Event System

This guide covers the event system used in MNE Analyze, not to be confused with the Event Manager plugin.

Overview

In addition to the Qt Framerork’s signal/slot system, MNE Analyze uses an event system for all communication between plugins. This event system is integrated in all plugins through the interface IPlugin, allowing all plugins to send and receive events. The event manager itself runs on a separate thread and runs on a cycle will check for buffered events and deliver them if available.

Sending Events

Events are sent using the Communicator class (applications/mne_analyze/libs/anShared/Management/communicator.h), using publishEvent(). When sending an event we pass an event type, and can also pass data though a QVariant. Below is a code snippet of the Filtering plugin broadcasting an event with data.

void Filtering::setFilterChannelType(const QString& sType)
{
    QVariant data;
    data.setValue(sType);
    m_pCommu->publishEvent(EVENT_TYPE::FILTER_CHANNEL_TYPE_CHANGED, data);
}

The string sType is added to QVariant data with setValue()

Receiving Events

To receive an event or a certain type, a plugin has to subscribe to that event type. This can be done in a plugin’s implementation of IPlugin’s getEventSubscriptions() by returning a vector of all the vent types the plugin is subscribing to. Below is a code snippet of the Averaging plugin subscribing to events.

QVector<EVENT_TYPE> Averaging::getEventSubscriptions(void) const
{
    QVector<EVENT_TYPE> temp;
    temp.push_back(SELECTED_MODEL_CHANGED);
    temp.push_back(FILTER_ACTIVE_CHANGED);
    temp.push_back(FILTER_DESIGN_CHANGED);
    temp.push_back(EVENT_GROUPS_UPDATED);
    temp.push_back(CHANNEL_SELECTION_ITEMS);
    temp.push_back(SCALING_MAP_CHANGED);
    temp.push_back(VIEW_SETTINGS_CHANGED);

    return temp;
}

Once subscribed, plugins can handle incoming events with handleEvent(). Below is how the Events plugin handles its events.

void AnnotationManager::handleEvent(QSharedPointer<Event> e)
{
    switch (e->getType()) {
        case EVENT_TYPE::NEW_ANNOTATION_ADDED:
            emit newAnnotationAvailable(e->getData().toInt());
            onTriggerRedraw();
            break;
        case EVENT_TYPE::SELECTED_MODEL_CHANGED:
            onModelChanged(e->getData().value<QSharedPointer<ANSHAREDLIB::AbstractModel> >());
            break;
        default:
            qWarning() << "[AnnotationManager::handleEvent] Received an Event that is not handled by switch cases.";
    }
}

Event Types

All event types are declared in applications/mne_analyze/libs/anShared/Utils/types.h in the enum EVENT_TYPE. Add a new event type by adding an entry to the list.