[Interest] how exactly do you replace Qt4's QWidget::create(WId, ...) ?

[Sze Howe Koh]

On Mon, 10 Aug 2020 at 00:53, René J.V. Bertin <rjvbertin at gmail.com> wrote:
>
> Hi,
>
> According to the documentation, where in Qt4/X11 one could create a "foreign" QWidget with QWidget::create(WId id, ...), in Qt5 one has to do something like
>
>             externalWindow = QWindow::fromWinId(id);
>             if (externalWindow) {
>                 externalParent = externalWindow->parent();
>                 theWidget = QWidget::createWindowContainer(externalWindow);
>             }
>
> (with externalParent required to reparent externalWindow before destroying the container).
>
> Except that when I do this, I get 2 windows (neither of which will show my content), and the original window gets resized even when I take care not to ask for that (not directly at least).
>
> I also see a series of
>
> QWidget::paintEngine: Should no longer be called
> QPainter::begin: Paint device returned engine == 0, type: 1
>
> on the terminal which I don't see if I just create a new QWidget .
>
> I guess I must be missing something?

I haven't seen the symptoms that you've described, but I've seen other
weirdness with QWidget::createWindowContainer() on foreign windows:
https://bugreports.qt.io/browse/QTBUG-40320

I don't think they've ever been resolved in Qt 5.


> Thanks,
> R.
>
> PS: goal here is to convert an old KDE4 screensaver to Qt5 - a cute project for a steamy sunday afternoon ;)

Regards,
Sze-Howe