[vtkusers] RE: User-defined ExitMethod to close an interactive vtk model by breaking threads to vtkRenderWindowInteractor and vtkRenderWindow gives Segmentation Fault

[Anwar Upal]

Dear Mr Prabhu Ramachandran & Other Users:

If I use a static member function instead of a static_cast, gdb gives the 
following error when compiling:
         carpus.cpp:798: cannot declare member function 
`carpus::MemberExitMethod(void *)' to have static linkage
         carpus.cpp: In function `static void carpus::MemberExitMethod(void 
*)':
         carpus.cpp:800: invalid use of member `carpus::iren' in static 
member function
         carpus.cpp:801: invalid use of member `carpus::renWindow' in 
static member function

where the line numbers are shown below:
         798:  static void carpus::MemberExitMethod(void *arg)
         799:  {
         800:    iren->Delete();
         801:    renWindow->Delete();
         802:  }

If I use a static_cast, then the program compiles successfully.  And the 
gdb debugger gives the following error at runtime when I press "q" to close 
the render window:
            Program received signal SIGSEGV, Segmentation fault.
            carpus::MemberExitMethod (this=0x0, arg=0x0) at carpus.cpp:800

where line 800 is as follows:
         798:  void carpus::MemberExitMethod(void *arg)
         799:  {
         800:    iren->Delete();  //*******************THIS IS LINE 
800*******************//
         801:    renWindow->Delete();
         802:  }

The associated code is listed in the previous message attached 
below.  Please let me know if there is anything else I can provide which 
may be helpful.

Thanks,
Anwar


PR>Its hard for people to figure out the problem with pure code. A trace 
from a debugger is usually
PR>more helpful. Try running your code with a debugger and see where it 
segfaults.
PR>Also try using a static member function instead of a static_cast etc. 
prabhu

>vtkRenderWindowInteractor's default exitMethod kills my application and 
>gui as well as the vtkRenderWindow.  We defined a user-defined exitMethod 
>to give control back to program by terminating the threads to 
>vtkRenderWindowInteractor and vtkRenderWindow.  This gives me a 
>segmentation fault when my exitMethod tries to break the threads.  Is 
>there another way...?
>
>I will show the relevant code below.  My program has a carpus class.  This 
>class has a method called carpalRender for rendering the carpus.  And a 
>new user-defined exitMethod to exit the vtk window opened by carpalRender.
>
>class carpus
>{
>private:
>
>   //I define these as members of carpus so that I can terminate the 
> threads from my exit method
>
>   vtkRenderWindowInteractor *iren;
>   vtkRenderWindow* renWindow;
>   vtkRenderer* scene_render;
>   ...
>
>public:
>   //render to show itself
>   void carpalRender(...);
>
>   //new exit method for vtkWindowInteractor so it does not terminate 
> application
>   void carpus::MemberExitMethod(void *arg);
>   ...
>};
>
>Now Here is the relevant code from the method carpus::carpalRender which 
>calls the ExitMethod.
>
>void carpus::carpalRender(...)
>{
>   ...
>   renWindow = vtkRenderWindow::New();
>   ...
>
>   // Create window interactor
>   iren = vtkRenderWindowInteractor::New();
>   ...
>
>   // set the user-defined C-style ExitMethod as the new exit method
>   iren->SetExitMethod (ExitMethod,NULL);
>
>   // Draw the resulting scene
>   renWindow->Render();
>
>   // Enable mouse interaction
>   iren->Start();
>
>   //since vtkRenderWindowInteractor does not give control back to 
> carpalRender
>   //any further code in carpalRender would not get executed
>};
>
>Now the following segment of code is the C-style exit method which then 
>executes another MemberExitMethod which is a member of the carpus class.
>
>//*********************>>> ExitMethod <<<<************************//
>   void ExitMethod(void *arg)
>   {
>     static_cast<carpus*>(arg)->MemberExitMethod(arg);
>   };
>
>//*********************>>> carpus::MemberExitMethod 
><<<<************************//
>   void carpus::MemberExitMethod(void *arg)
>   {
>     iren->Delete();
>     renWindow->Delete();
>  };
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