The function window()->windowHandle(); always returns nullptr in my custom widget.

[Paul Xu]

I want to obtain the QWindow handler within the constructor of my custom widget, but it always returns a null pointer.

class MyWidget : public QWidget {
    Q_OBJECT

 public:
    MyWidget() {
           QWindow *win = window()->windowHandle();
           std::println("win equals nullptr: {}", win == nullptr);  // prints true
    }
};

How can I get the QWindow handler ?

[Pl45m4]

@Paul-Xu

AFAIK the widget has no valid window handle while being constructed.
Try after the widget is shown on screen.

[hskoglund]

The QWindows has not been rendered yet, try holding your horses for say 20 ms:

...
   MyWidget() {
      QTimer::singleShot(20,[this] {
           QWindow *win = window()->windowHandle();
           std::println("win equals nullptr: {}", win == nullptr);  // prints true
      });
   }

[Pl45m4]

@Paul-Xu

AFAIK the widget has no valid window handle while being constructed.
Try after the widget is shown on screen.

[Paul Xu]

@Pl45m4

void MyWidget::showEvent(QShowEvent *event) {
    if(this->win == nullptr) {
           this->win = window()->windowHandle();
   }
   QWidget::showEvent(event);
}

Apart from this way, I wonder if there are any other more elegant solutions?

[JonB]

@Paul-Xu
If it works (I would have put it after the QWidget::showEvent(event);) then it's fine, what is not "elegant" about it?