[vtkusers] the New QVTKOpenGLWidget

[Mathieu Westphal]

Hi Elvis,

This is down to Qt developpers only, see this 2013 change :
https://codereview.qt-project.org/#/c/68683/
And associated code :
https://code.woboq.org/qt5/qtbase/src/widgets/kernel/qwindowcontainer.cpp.html#101

QTabWidget will never force it to be a native widget though and even if it
was, you will be informed as we do put a QVTKOpenGLWidget in a QTabWidget
in ParaView.
My Advice is to use the new QVTKOpenGLWidget in your case.

Best regards,

Mathieu Westphal


On Fri, Sep 21, 2018 at 6:48 PM Elvis Stansvik <elvis.stansvik at orexplore.com>
wrote:

> 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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