[Interest] How can I block the WindowActivate and FocusIn events when showing window programmatically

[Yili Pan]

Hi John:

Thanks:) Actually we have some problem with the resize and move also, I can
understand most of your solution, but could you explain more about why
calling doing this part
                moving = true;
                movedWidget = somewidget;
                somewidget->move();
                return <whatever>;

inside of a event filter?

Thanks,
-Yili


On Fri, Oct 31, 2014 at 11:56 AM, John Weeks <john at wavemetrics.com> wrote:

> It's the same situation with Move and Resize events. In Qt 4, you could do
> this:
>
> bool myclass::eventFilter(QObject * target, QEvent *event)
> {
>         static bool moving = false;
>
>         case QEvent::move:
>
>                 // In Qt 4, the move event comes synchronously, so we know
> that only our call to QWidget::move
>                 // can cause a reentrant call here.
>                 if (moving)
>                         return;
>
>                 moving = true;
>                 ... call QWidget::move ....
>                 moving = false;
> }
>
>
> But in Qt 5 the Move event is put on the queue and delivered
> asynchronously. So now I have this sort of code:
>
> class myclass
> {
>         ...
>
>         private:
>                 bool moving;
>                 QWidget * movedWidget;
> };
>
> bool myclass::eventFilter(QObject * target, QEvent *event)
> {
>         somewidget = qobject_cast<QWidget *>(target);
>
>         case QEvent::move:
>                 // in Qt 5, the call to QWidget::move doesn't cause a
> reentrant call here, it triggers
>                 // another move event later on. So we have to store away
> info on this call to QWidget::move,
>                 // and detect that move event later on when it looks like
> other move events.
>                 if (moving && somewidget == movedWidget)
>                 {
>                         moving = false;
>                         movedWidget = NULL;             // not at C++11
> yet!
>                         return false;
>                 }
>
>                 moving = true;
>                 movedWidget = somewidget;
>                 somewidget->move();
>                 return <whatever>;
> }
>
> I put in a check on the widget that was moved out of paranoia that some
> other move event could sneek in while I was waiting. In our case, we have
> the same filter on multiple widgets.
>
> Warning: I could have made some typo in the process of abstracting the
> method from much more complex code...
>
> -John Weeks
>
> On Oct 31, 2014, at 7:35 AM, Yili Pan <pyl0420 at gmail.com> wrote:
>
> > Hi Bo:
> >
> > Thank you for the reply!
> >
> > I do not want to filter out all the WindowActivate or FocusIn event
> tough, only these are triggered by calling QWidget::show(). But because the
> events are processed asynchronously in Qt5, when I catch them in the
> eventfilter, I don't know whether they are originated from calling show()
> or they are spontaneous event caused by manual interaction. I also tried to
> filter out the event by telling whether they are spontaneous, but
> unfortunately no matter where they originate from, they are spontaneous
> (could this be a bug??). Any thoughts or suggestion :)
> >
> > Thank you!
> >
> > -Yili
> >
> > On Fri, Oct 31, 2014 at 4:01 AM, Bo Thorsen <bo at vikingsoft.eu> wrote:
> > Den 30-10-2014 20:30, Yili Pan skrev:
> > > Hi:
> > >
> > > We want to block the widget's WindowActivate and FocusIn event
> > > triggered by calling its show() function, with Qt4,  we used to do
> > > that by setting flag before and after show() and filter out the event
> > > in eventfilter based on the flag.  But with Qt5, the events are
> > > processed asynchronously, we cannot block the event in the same way
> > > anymore.
> > >
> > > Any ideas how I can identify those events that are caused by calling
> > > QWdiget::show() and filter them out?
> >
> > You can use an event filter for this. Take a look at the documentation
> > for QObject::installEventFilter, it should be simple to follow.
> >
> > Bo.
> >
> > --
> > Viking Software
> > Qt and C++ developers for hire
> > http://www.vikingsoft.eu
> >
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>
> -John
>
>
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