custom Qt event is not delivered (event flow: Widget inside -> QMainWindow)

Question

I have a QMainWindow-derived Widget that contains a QGLWidget-derived Widget. I have a custom Event that will get fired from within the GLWidget's paintGL() method that way (the notification shall be asynchonous, that's why I'd like to post an event):

QCoreApplication::postEvent(parent(),new ColpickEvent(rgb, pickPoint));

The event looks like this (very simple, no capsuling of data):

#define COLORPICK_EVENT QEvent::Type(31337)
class ColpickEvent : public QEvent
{
public:
    ColpickEvent(QRgb col, const QPoint& pos)
        : QEvent(COLORPICK_EVENT), Color(col), PixelPos(pos) {};
    QColor  Color;
    QPoint  PixelPos;
};

The MainWindow overrides QObject::event(QEvent*) like this:

#define EVENT_TYPE(ClassName) { ClassName *e = static_cast<ClassName*>(event)
#define END_EVENT } break
#define ACCEPT_EVENT e->accept(); return true
bool MainWindow::event(QEvent* event)
{
    switch(event->type())
    {
    /*... handle other events ...*/
    case COLORPICK_EVENT:
        EVENT_TYPE(ColpickEvent);
        // do something with the data provided by the event ...
        ACCEPT_EVENT;
        END_EVENT;
    /*... handle other events ...*/
    }
    return QMainWindow::event(event);
}

What happens is, that my ColpickEvent never seems to get dispatched to MainWindow. Any ideas why this happens (or actually doesn't happen)?

you should post an answer with your solution and accept it so it's clearer for future visitors — ratchet freak
You're right, but I found my solution too quickly - I wasn't allowed to add an answer by myself for 8 hours. — St0fF

St0fF St0fF · Accepted Answer · 2014-01-10T21:55:59

OOPS.

As the top level widget was derived from QMainWindow, it needed to have a centralWidget. Somehow it wasn't possible to set the GLWidget as centralWidget, as I needed a Layout to overlay other widgets on top of it. So the centralWidget of MainWindow is a simple QWidget "w" with a GridLayout. The GLWidget is added to the Layout, that way its parent was changed to "w".

Because of this, the solution is simply enough:

QCoreApplication::postEvent(parent()->parent(),new ColpickEvent(rgb, pickPoint));

(see the double-parent-call).

custom Qt event is not delivered (event flow: Widget inside -> QMainWindow)

1 Answers