Determine source of QKeyEvent - c++

Question

I have a Qt application with multiple widgets showing buttons at the same time. In certain circumstances, I want key presses to be sent to one of the widgets, even if that widget doesn't have focus. To do this, I have overridden keyPressEvent() in the master widget (that owns all subwidgets in this application) and re-send the key event to the subwidget if it doesn't have focus using code similar to this:
if (!someWidget->hasFocus())
{
QApplication::sendEvent(someWidget, keyEvent);
}
This works great as long as someWidget handes said event. If it ignores it, then it enters a nasty infinite recursive loop since events flow up to parents.
Is there a way to know where an event came from so I can prevent this infinite loop? I'm thinking of something like this:
if (!someWidget->hasFocus() && (keyEvent->source != someWidget))
{
QApplication::sendEvent(someWidget, keyEvent);
}
Or is there a different way I can prevent this from happening?

Answer 1

When you use signals and slots mechanism you can call sender() which can give you information, but here you can do next: use eventFilter which can give you information about every QObject which sends events to mainWindow, so you can catch event and sender
bool MainWindow::eventFilter(QObject *obj, QEvent *event)
{
if(event->type() == QEvent::KeyPress)//your keyPressEvent but with eventFilter
if(!someWidget->hasFocus() && obj != someWidget)//your focus and source checkings, obj is object which send some event,
// but eventFilter catch it and you can do something with this info
{
//do something, post event
}
return QObject::eventFilter(obj, event);
}
Don't forget
protected:
bool eventFilter(QObject *obj, QEvent *event);
Maybe you need use QKeyEvent, so cast QEvent if you sure that event->type() == QEvent::KeyPress. For example:
QKeyEvent *key = static_cast<QKeyEvent*>(event);
if(key->key() == Qt::Key_0)
{
//do something
}