[Insight-users] [vtkusers] QWidget:Must construct a QApplication before a QPaintDevice

[Dženan Zukić]

Since I use VTK 5.6.1, and not the current development version I do
not have QVTKApplication.h. The following code works (screenshot
attached) on my computer:

#include "qmainwindow.h"
 #include "qapplication.h"
 #include <QVTKWidget.h>
 //#include <QVTKApplication.h>
 #include <vtkRenderWindow.h>
 #include <vtkRenderer.h>
 #include <vtkTextSource.h>
 #include <vtkVectorText.h>
 #include <vtkPolyDataMapper.h>
 #include <vtkActor.h>
 int main( int argc, char **argv )
 {
 QApplication app(argc,argv);
 QMainWindow *mainWindow = new QMainWindow;
  mainWindow->setFixedSize(640,360);
 QVTKWidget *widget = new QVTKWidget;
  mainWindow->setCentralWidget(widget);
 vtkTextSource *text = vtkTextSource::New();
  text->SetText("Hello World!");
  text->BackingOff();
 vtkVectorText *vectorText = vtkVectorText::New();
  vectorText->SetText("QVTKWidget");
 vtkPolyDataMapper *textMapper = vtkPolyDataMapper::New();
  textMapper->SetInput(text->GetOutput());
 vtkPolyDataMapper *vectorTextMapper = vtkPolyDataMapper::New();
  vectorTextMapper->SetInput(vectorText->GetOutput());
 vtkActor *textActor = vtkActor::New();
  textActor->SetMapper(textMapper);
 vtkActor *vectorTextActor = vtkActor::New();
  vectorTextActor->SetMapper(vectorTextMapper);
 vtkRenderer *renderer = vtkRenderer::New();
  renderer->SetBackground(0.4,0.6,0.8);
  renderer->AddActor(textActor);
  renderer->AddActor(vectorTextActor);
 vtkRenderWindow *renderWindow = vtkRenderWindow::New();
  renderWindow->AddRenderer(renderer);
  renderWindow->SetStereoTypeToDresden();
 widget->SetRenderWindow(renderWindow);
 mainWindow->show();
 app.aboutQt();
    return app.exec();
 }
2011/8/15 Leonid Dulman <leonid_dulman at yahoo.co.uk>
>
> I changed release VTK  building to Debug (VC 2010), but in Windows 7 SP1 have got message
> "QWidget:Must construct a QApplication before a QPaintDevice"
> Thank you Leonid
>
>
> --- On Mon, 15/8/11, Dženan Zukić <dzenanz at gmail.com> wrote:
>
> From: Dženan Zukić <dzenanz at gmail.com>
> Subject: Re: [vtkusers] QWidget:Must construct a QApplication before a QPaintDevice
> To: "Leonid Dulman" <leonid_dulman at yahoo.co.uk>
> Cc: vtkusers at vtk.org
> Date: Monday, 15 August, 2011, 10:16
>
> Does this help:
> http://dzenanz.wordpress.com/2011/04/05/qwidget-must-construct-a-qapplication-before-a-qpaintdevice/
>
> On Mon, Aug 15, 2011 at 09:09, Leonid Dulman <leonid_dulman at yahoo.co.uk> wrote:
>
> Hi to All
> In next Example
> #include "qmainwindow.h"
>  #include "qapplication.h"
>
>  #include <QVTKWidget.h>
>  #include <QVTKApplication.h>
>
>  #include <vtkRenderWindow.h>
>  #include <vtkRenderer.h>
>  #include <vtkTextSource.h>
>  #include <vtkVectorText.h>
>  #include <vtkPolyDataMapper.h>
>  #include <vtkActor.h>
>
>  int main( int argc, char **argv )
>  {
>  QVTKApplication app(argc,argv);
>  QMainWindow *mainWindow = new QMainWindow;
>   mainWindow->setFixedSize(640,360);
>
>  QVTKWidget *widget = new QVTKWidget;
>   mainWindow->setCentralWidget(widget);
>
>  vtkTextSource *text = vtkTextSource::New();
>   text->SetText("Hello World!");
>   text->BackingOff();
>  vtkVectorText *vectorText = vtkVectorText::New();
>   vectorText->SetText("QVTKWidget");
>  vtkPolyDataMapper *textMapper = vtkPolyDataMapper::New();
>   textMapper->SetInput(text->GetOutput());
>  vtkPolyDataMapper *vectorTextMapper = vtkPolyDataMapper::New();
>   vectorTextMapper->SetInput(vectorText->GetOutput());
>  vtkActor *textActor = vtkActor::New();
>   textActor->SetMapper(textMapper);
>  vtkActor *vectorTextActor = vtkActor::New();
>   vectorTextActor->SetMapper(vectorTextMapper);
>  vtkRenderer *renderer = vtkRenderer::New();
>   renderer->SetBackground(0.4,0.6,0.8);
>   renderer->AddActor(textActor);
>   renderer->AddActor(vectorTextActor);
>  vtkRenderWindow *renderWindow = vtkRenderWindow::New();
>   renderWindow->AddRenderer(renderer);
>   renderWindow->SetStereoTypeToDresden();
>
>  widget->SetRenderWindow(renderWindow);
>  mainWindow->show();
>  app.aboutQt();
>     return app.exec();
>  }
>
> I have got massage "QWidget:Must construct a QApplication before a QPaintDevice" only in Windows 7 SP1, in Windows XP and linux I have no any problems
>
> My installation is
> Qt 4.7.3
> VTK 5.9.0 (from git)
> Thank you. Leonid
>
>
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