implementing custom completer, popup window steal the focus - c++

Question

I need to implement custom completer, similar to QCompleter but containing customized widgets. I got stuck at the very beginning, I can't make the popup work as it should work. In the following example I attach a completer (well, just a plain widget) to the first line edit. The second line edit is there just to test the focus in/out behavior. The problem is that when the popup displays, it steals the focus from the line edit. But this is not what I want, I want to be able to keep typing in the line edit. I tried several other options as commented out in the code below, but non of them worked.
#include <QApplication>
#include <QLineEdit>
#include <QHBoxLayout>
#include <QWidget>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QWidget container;
QLineEdit editor;
QLineEdit editor2;
QHBoxLayout layout(&container);
layout.addWidget(&editor);
layout.addWidget(&editor2);
QWidget completer; // or QWidget completer(&editor);?
//completer.setFocusProxy(&editor); // tried this, but it does not help
completer.setWindowFlags(Qt::Popup);
// the following lines are an alternative to Qt::Popup but the window
// does not close automatically, which is a problem
// e.g. when moving or resizing the parent window
//completer.setAttribute(Qt::WA_ShowWithoutActivating);
//completer.setWindowFlags(Qt::Tool | Qt::FramelessWindowHint);
QObject::connect(&editor, &QLineEdit::textEdited,
[&] {
completer.resize(editor.width(), 100);
completer.move(editor.mapToGlobal(QPoint(0, editor.height())));
completer.show();
// editor.setFocus(); // does not help either
});
container.show();
return a.exec();
}
How to implement custom completer?
UPDATE: From the docs, I read that "A popup widget is a special top-level widget that sets the Qt::WType_Popup widget flag, e.g. the QMenu widget. When the application opens a popup widget, all events are sent to the popup. Normal widgets and modal widgets cannot be accessed before the popup widget is closed."
So it seems that when I open a popup it automatically receives the events and therefore I have to forward the events to the line edit using QCoreApplication::sendEvent(editor, event); inside my Completer::keyPressEvent. This seems to work fine except the fact that the cursor in the line edit is not visible or not blinking.

Answer 1

Just apply this method to your completer widget:
setWindowFlags(Qt::Tool | Qt::FramelessWindowHint|Qt::WindowStaysOnTopHint);
It works for me.