vtkCaptionWidget interferes with Qt C++ Application quit

Support
1

I am using vtkCaptionWidget to annotate the 2D image loaded in qvtkwidget. However once the caption widget is placed on the image QApplication::exit(0) doesn’t work. Even if the window is closed by calling close() function, application runs in the background.

This is my code for caption written in a clickcallback function

auto* iren = static_cast<vtkRenderWindowInteractor*>(caller);

    vtkSmartPointer<vtkCoordinate> coordinate = vtkSmartPointer<vtkCoordinate>::New();
    coordinate->SetCoordinateSystemToDisplay();
    coordinate->SetValue(iren->GetEventPosition()[0],iren->GetEventPosition()[1],0);

    double* world = coordinate->GetComputedWorldValue(iren->GetRenderWindow()->GetRenderers()->GetFirstRenderer());
    double pos[3] = {world[0], world[1], 0};

    std::string str = annotText.toStdString();
    const char* cText = str.c_str();

    vtkTextProperty *tprop = vtkTextProperty:: New();
    tprop->SetFontFamilyToArial();
    tprop->SetFontSize(14);
    tprop->BoldOn();
    tprop->ShadowOn();
    tprop->ItalicOn();
    tprop->SetColor(1, 1, 1);

    vtkNew<vtkCaptionRepresentation> captionRepresentation;
    captionRepresentation->GetCaptionActor2D()->GetTextActor()->SetTextScaleMode(1);
    captionRepresentation->GetCaptionActor2D()->SetCaptionTextProperty(tprop);
    captionRepresentation->GetCaptionActor2D()->SetCaption(cText);
    captionRepresentation->GetCaptionActor2D()->BorderOn();
    captionRepresentation->GetCaptionActor2D()->ThreeDimensionalLeaderOff();
    captionRepresentation->GetCaptionActor2D()->SetMaximumLeaderGlyphSize(10);
    //captionRepresentation->GetCaptionActor2D()->GetPositionCoordinate()->SetCoordinateSystemToViewport();
    captionRepresentation->SetPosition(0.7,0.3);
    captionRepresentation->SetPosition2(0.1,0.03);
    captionRepresentation->SetAnchorPosition(pos);

    vtkNew<vtkCaptionWidget> captionWidget;
    captionWidget->SetInteractor(iren);
    captionWidget->SetRepresentation(captionRepresentation);
    captionWidget->On();
    iren->Start();

This is the code in quit button click

    QApplication::exit(0);
    ui->~MainWindow();

What could be causing this. This doesn’t arise on placing any other widgets like distance or angle widget.

2

Hello,

Is there any reason to explicitly call QApplication::exit()? Once the application’s last QWidget gets destroyed, the UI’s event loop (QApplication::exec()) returns. If it is the last call in your program, the program finishes. You don’t need to call QApplication::exit() explicitly. Also, you’re not supposed to call a destructor like that. It either gets called by delete or when a stack or static object goes out of scope.

take care,

Paulo

3

You can try calling the MainWindow::close() slot from the button click to finish your program.

4

Hello… I have tried calling close(). The window shuts down. However the next time i try to build the application, previous instance is seen as crashed - which means it was running in background and didn’t have a normal exit.

5

This issue occurs only when we place the caption widget. No problem whatsoever otherwise. Was wondering why.

6

Do you have other Qt applications other than Qt Creator and your own?

7

Apologies for the late reply. No other applications other than Qt creator and mine are on the device. Could you say what implications are there if another one exists

8

Ill-written Qt applications may leave the Qt dynamic libraries in memory. I’ve seen such issue before.

9

Pelase, take a look at this: resources - Correct way to quit a Qt program? - Stack Overflow

And, again, don’t call the window’s destructor like you did. BTW, never explictly call any destructor.

1 Like
10

This hasn’t been resolved yet. Can’t figure out why placing a widget is affecting the exit of application. Searching for any possible background processes

11

Hello,

I believe it’s time to use a debugger. Do you have Qt and VTK compiled in debug mode?

best,

PC