How can I make a QWidget semitransparent to events? - qt

Question

I've seen similar questions but no answers that fit what I need. I want an invisible widget that lives on top of my whole application (no problems here). I want this widget to catch events so that I can print stuff about them, record them, whatever. I currently have an event filter hooked up that does this just fine. Then I want it to let the event go through to whatever is behind the widget. So for instance, if I try to push a button, the invisible widget should notice that a press happened on that spot, and then the button should actually be pressed. Can this be done in a simple way, or am I going to have to write code to simulate all the events beneath the invisible widget?

Answer 1

From all the information you disclosed in the comments, I suggest you filter the event as previously discussed, and then use QCoreApplication::sendEvent to forward the desired events to the invisible widget. It will then propagate the event accordingly to its children.
EDIT: OK, here is quick example that includes a QObject based event filter, that will filter the events for a widget, if the event is mouse event, it will be left for the widget to handle and print the output, if the event is a key event, it will be filtered and not forwarded back to the widget:
The event filter class:
class EventInfo : public QObject {
Q_OBJECT
public:
explicit EventInfo(QObject *parent = 0) : QObject(parent) {}
bool eventFilter(QObject *, QEvent *e) {
if (e->type() == QEvent::MouseButtonRelease){
qDebug() << "click event not filtered";
return false;
}
if (e->type() == QEvent::KeyRelease) {
QKeyEvent *event = static_cast<QKeyEvent *>(e);
if (event) qDebug() << "key" << event->key() << "filtered";
return true;
}
return false;
}
};
The widget:
class Widget : public QWidget {
Q_OBJECT
public:
Widget(QWidget *parent = 0) : QWidget(parent) {}
protected:
void mouseReleaseEvent(QMouseEvent *e) {
qDebug() << "widget clicked at position" << e->pos();
}
void keyReleaseEvent(QKeyEvent *e) {
qDebug() << "pressed key" << e->key();
}
};
main.cpp:
int main(int argc, char *argv[]) {
QApplication a(argc, argv);
Widget w;
EventInfo info;
w.installEventFilter(&info);
w.show();
return a.exec();
}
Testing output to show that keyboard events are filtered and mouse press events are forwarded to the widget:
click event not filtered
widget clicked at position QPoint(352,230)
key 70 filtered
click event not filtered
widget clicked at position QPoint(405,163)
key 87 filtered