[vtk-developers] Delayed mouse interaction due to event-loop bug in Qt5

[David Gobbi]

My strong preference is only call Render() within Qt's paintEvent(),
and to disable Render() everywhere else.  Then, when I want VTK
to render, I call update() on my QWidget to let Qt know that it has
to re-paint.

This keeps things nicely synchronized between VTK and Qt, which
is especially important for things like resizing the window.

Another thing that I do differently from QVTKWidget is that I install
a dummy QPaintEngine so that Qt never executes any drawing
commands within the widget, but that's a separate issue from the
event loop bug.

 - David


On Mon, Apr 10, 2017 at 1:13 PM, Elvis Stansvik <
elvis.stansvik at orexplore.com> wrote:

> 2017-04-10 21:10 GMT+02:00 Elvis Stansvik <elvis.stansvik at orexplore.com>:
> > 2017-04-10 20:07 GMT+02:00 Pat Marion <james.patrick.marion at gmail.com>:
> >> Hi Elvis,
> >>
> >> In prior emails you mentioned that you use a QVTKWidget subclass (or
> >> QVTKWidget2?) that contains a workaround for this event issue.  Is this
> >> class something that you can share?  Do you recommend using this
> workaround,
> >> or is the patched qt5.5 preferable?
> >
> > Sure, I'm attaching VTKWidget.h/cpp, which contains the QVTKWidget
> > subclass I'm currently using.
> >
> > If I remember correctly, it was David Gobbi who led me to this
> > workaround, so he should have the credit.
>
> My bad, it was Clint and David together who helped me out. This was
> the original thread:
>
>     http://public.kitware.com/pipermail/vtkusers/2016-July/095802.html
>
> Elvis
>
> >
> > It's of course preferable to use a fixed Qt (5.6 or higher, or patched
> > 5.5.1), but I'll use this workaround until the patched package is in
> > the xenial-updates repo (the upload to xenial-proposed seems to take
> > some time, I guess the approvers are busy).
> >
> > Elvis
> >
> >>
> >> Pat
> >>
> >> On Mon, Mar 20, 2017 at 4:55 PM, Elvis Stansvik
> >> <elvis.stansvik at orexplore.com> wrote:
> >>>
> >>> > On Mon, Jul 13, 2015 at 16:51:34 -0400, Ben Boeckel wrote:
> >>> >> On Mon, Jul 13, 2015 at 15:00:56 -0400, Ben Boeckel wrote:
> >>> >>>     https://codereview.qt-project.org/#/c/115531/
> >>> >>
> >>> >> Applying this patch (with one conflicting hunk) to 5.5.0 fixes the
> >>> >> problem for me. I'll poke the review to see if some movement can't
> be
> >>> >> made.
> >>> >
> >>> > It looks like the patch has been merged for 5.6.0 (due at the end of
> >>> > October).
> >>>
> >>> Just in case anyone is in the same boat like me, hitting this bug on
> >>> Ubuntu 16.04 LTS (which has Qt 5.5.1), just FYI I'm trying to get an
> >>> SRU (Stable Release Update) going with this fix:
>
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