[Plugins] Asynchronous drawing

[Fabien-B]

Hello,
Is it possible, or could it be possible in the future to allow plugins to draw asynchronously ?

Consider this code as a minimal example:

void LC_myPlugin::execComm(Document_Interface *doc, QWidget *parent, QString cmd) {
    QTimer* timer = new QTimer(this);
    timer->setSingleShot(true);

    connect(timer, &QTimer::timeout, this, [=]() {
        qDebug() << "timer expired!";
        QPointF start(0,0);
        QPointF end(100, 200);
        doc->addLine(&start, &end);
    });

    timer->start(1000);
}

It crashes with a segfault because the doc pointer is a local variable in the calling method: https://github.com/LibreCAD/LibreCAD/blob/master/librecad/src/main/qc_applicationwindow.cpp#L724-L737

I would like to be able to access to all drawing methods from within the Qt event loop.

This minimal example demonstrate it with a timer, but the drawing could be triggered by any Qt signal.

[dxli]

The easiest could be adding an interface to accept a smart pointer of doc,

void LC_myPlugin::execComm(std::unique_ptr<Document_Interface> doc, QWidget *parent, QString cmd) {
// move the ownership to the current LC_myPlugin instance
this->m_doc = std::move(doc);
....
connect(timer, &QTimer::timeout, this, [this]() {
        qDebug() << "timer expired!";
        QPointF start(0,0);
        QPointF end(100, 200);
        m_doc->addLine(&start, &end);
    });
....
}