Fix Bug between addText3D and QVTKWidget

[booksuper]

When using addtext3d to display 3D text in qvtkwidget, an error "access conflict occurs when reading position 0x000000000000008" will be reported. The reason is that "render - > render()" has been used in addtext3d once, but to send 3D text to qvtkwidget window, execute "UI - > qvtkwidget - > setrenderwindow (viewer - > getrenderwindow());Viewer - > setupinteractor (UI - > qvtkwidget - > getinteractor()); ", which is equivalent to repeated rendering, resulting in pointer out of bounds.
After experiments, it is OK to delete "render - > render()" and it works normally when it does not interact with qvtkwidget

[larshg]

Instead of commenting the line, just remove it.

Which version of VTK have you tested with?

I can reproduce it with VTK 9.0.1, so unless you have tested VTK 6,7,8 I'd suggest to wrap it in:

      #if VTK_MAJOR_VERSION < 9
      renderer->Render ();
      #endif

[booksuper]

Instead of commenting the line, just remove it.

Which version of VTK have you tested with?

I can reproduce it with VTK 9.0.1, so unless you have tested VTK 6,7,8 I'd suggest to wrap it in:

      #if VTK_MAJOR_VERSION < 9
      renderer->Render ();
      #endif

[booksuper]

Instead of commenting the line, just remove it.
Which version of VTK have you tested with?
I can reproduce it with VTK 9.0.1, so unless you have tested VTK 6,7,8 I'd suggest to wrap it in:

      #if VTK_MAJOR_VERSION < 9
      renderer->Render ();
      #endif

I have tested with vtk8.0.0, but vtk6 and 7 have not been tested

[larshg]

Eventually someone could test it on linux, but for now, since its the only place its called, I'll be fine with just removing it.
A render call will eventually be called later, so the text will definitely appear at some point 😄

[larshg]

FYI. You can just commit to your branch and push it again with new changes - you don't have to create a new pull request.

[booksuper]

FYI. You can just commit to your branch and push it again with new changes - you don't have to create a new pull request.

Thanks for your suggestion
Thanks for your advice. This is my first pull request, and your suggestion has helped me a lot. I'm going to change it like this. Do you think it's feasible
#if VTK_MAJOR_VERSION < 8
renderer->Render ();
#endif

[larshg]

I got time to test it with vtk 6.3 and it seg faults as well so let's just remove the line entirely.

[booksuper]

I got time to test it with vtk 6.3 and it seg faults as well so let's just remove the line entirely.

Thanks for your great work. That is great!

[booksuper]

I've been thinking about the essential reason for this bug recently, but I'm not a computer major. This problem is a little difficult for me. After consulting a lot of blogs and books, I guess the reason for the error is that the memory access is out of bounds. I'm not sure, so I'd like to consult you. I look forward to your reply. Thank you

[mvieth]

I tested (with VTK 9.0.1) and found:

• In connection with Qt/QVTKWidget, addText3D segfaults without the fix, but works with the fix
• if PCLVisualizer is used without Qt/QVTKWidget, addText3D works fine with and without this fix

So looks good to me

[booksuper]

I tested (with VTK 9.0.1) and found:

• In connection with Qt/QVTKWidget, addText3D segfaults without the fix, but works with the fix
• if PCLVisualizer is used without Qt/QVTKWidget, addText3D works fine with and without this fix

So looks good to me

In the VTK 8.0.0，my test is the same as yours