[vtkusers] the New QVTKOpenGLWidget

[Elvis Stansvik]

Den tors 23 aug. 2018 11:09Mathieu Westphal <mathieu.westphal at kitware.com>
skrev:

> Hello list,
>
> If you are working on a VTK/Qt application this information should
> interest you.
> Sometime ago, a new QVTKOpenGLWidget implementation has been added to VTK,
> while the old one has been moved to QVTKOpenGLSimpleWidget.
> The last fixes for this change have just been merged, so make sure to use
> VTK master to test this.
>
> *1. Why is there a new widget and what does it do ?*
> We have been having some issues reported for the old widget, and the old
> widget could not support quad buffer stereo rendering by design.
> Has it is a needed feature in ParaView, a reimplementation was necessary.
> This new widget fix most of the reported issues with the old widget as well
> as adding stereo support.
>
> *2. Why keeping the old widget around then ?*
> Due to Qt limitations, this new implementation does not support very well
> being a native widget.
> But native widget are sometimes mandatory, for example within QScrollArea
> and QMDIArea, so the
>

Do you know what other containers apart from QScrollArea will require
native widget? Will QTabWidget?

Asking because we are planning to possibly put one of our VTK views in a
tab widget, but would really like to benefit from some of the improvements
in the new VTK widget (respect for fractional device pixel ratio mostly).

If tab widget will require native, then I should really brush up an old MR
of mine that fixes fractional device pixel ratio in the "old" native
widget. I should do this anyway of course, but now I've heard that 8.2
might be around the corner, making it more urgent to do that asap.

Elvis

QVTKOpenGLSimpleWidget should be used when in needs of VTK rendering in the
> contact of Qt native widget.
>
> Also it allows users to switch back to the old widget if necessary.
>
> *3. I'm not sure what native widgets are, what should I do in my
> application ?*
>
> Here are the different situation :
>
>    1. Your Qt application only uses a central QVTKOpenGLWidget for
>    rendering:
>    -> Nothing to do, just build with last master and make sure all is
>    working well
>    2. Your Qt application only uses QVTKOpenGLWidget within QScrollArea
>    or QMDIArea, or manually set widgets to be native and you are not
>    interested by stereo rendering.
>     -> Change all your QVTKOpenGLWidget to QVTKOpenGLSimpleWidget and you
>    are good to go
>    3. Your application uses a non-native QVTKOpenGLWidget for rendering
>    as well as native QVTKOpenGLWidget for rendering (eg: ParaView, with the
>    central rendering widget and the color map editor rendering widget in
>    scroll areas) :
>     -> Use QVTKOpenGLWidget for non-native widgets and
>    QVTKOpenGLSimpleWidget for native ones. The later will never support stereo.
>
>
> *4. I followed your recommendation but I see some strange
> stuff/bugs/rendering issues*
> Even if this new class has been tested extensively and will be used in the
> next ParaView release, It may still contains some issues. Feel free to
> discuss them in this mailing list or on our gitlab
> <https://gitlab.kitware.com/vtk/vtk>.
>
> Best regards,
>
> Mathieu Westphal
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