[vtkusers] wxVTKRenderWindowInteractor use question

[Dean Inglis]

not sure if Im phrasing this correctly but I am
trying to subclass a wx.Frame and during its initialization,
set up a wxVTKRenderWindowInteractor.  In the
example code that appends the file
VTK/Wrapping/Python/vtk/wx/wxVTKRenderWindowInteractor.py
an application instance must first be created:
<snip>
import wx
import vtk
from vtk.wx.wxVTKRenderWindowInteractor import wxVTKRenderWindowInteractor

#--------------------------------------------------------------------
def simpleExample():
    """Like it says, just a simple example
    """
    # every wx app needs an app
    app = wx.PySimpleApp()

    # create the top-level frame, sizer and wxVTKRWI
    frame = wx.Frame(None, -1, "wxVTKRenderWindowInteractor", 
size=(400,400))
    widget = wxVTKRenderWindowInteractor(frame, -1)
    sizer = wx.BoxSizer(wx.VERTICAL)
    sizer.Add(widget, 1, wx.EXPAND)
    frame.SetSizer(sizer)
    frame.Layout()

    # It would be more correct (API-wise) to call widget.Initialize() and
    # widget.Start() here, but Initialize() calls RenderWindow.Render().
    # That Render() call will get through before we can setup the
    # RenderWindow() to render via the wxWidgets-created context; this
    # causes flashing on some platforms and downright breaks things on
    # other platforms.  Instead, we call widget.Enable().  This means
    # that the RWI::Initialized ivar is not set, but in THIS SPECIFIC CASE,
    # that doesn't matter.
    widget.Enable(1)

    widget.AddObserver("ExitEvent", lambda o,e,f=frame: f.Close())

    ren = vtk.vtkRenderer()
    widget.GetRenderWindow().AddRenderer(ren)

# later on in the code the app main loop is activated
<snip>

but I would like to do something like the following:


<snip>
import wx
import vtk
from vtk.wx.wxVTKRenderWindowInteractor import wxVTKRenderWindowInteractor

class MyFrame(wx.Frame):

    def __init__(self, parent, title):
        wx.Frame.__init__(self, parent, -1, title,
                          size=wx.Size(400,400))

        # create the top-level frame, sizer and wxVTKRWI
        widget = wxVTKRenderWindowInteractor(self, -1)        sizer = 
wx.BoxSizer(wx.VERTICAL)
        sizer.Add(widget, 1, wx.EXPAND)
        self.SetSizer(sizer)
        self.Layout()

    # It would be more correct (API-wise) to call widget.Initialize() and
    # widget.Start() here, but Initialize() calls RenderWindow.Render().
    # That Render() call will get through before we can setup the
    # RenderWindow() to render via the wxWidgets-created context; this
    # causes flashing on some platforms and downright breaks things on
    # other platforms.  Instead, we call widget.Enable().  This means
    # that the RWI::Initialized ivar is not set, but in THIS SPECIFIC CASE,
    # that doesn't matter.
        widget.Enable(1)

        widget.AddObserver("ExitEvent", lambda o,e,f=self: f.Close())

        ren = vtk.vtkRenderer()
        widget.GetRenderWindow().AddRenderer(ren)
<snip>

and subclass the application so that in its OnInit method
instantiates the subclassed frame with the vtkRWI:


class App(wx.App):

    def OnInit(self):
        self.frame = MyFrame(None,'test')
        self.frame.Show()
        return True

if __name__ == '__main__':
    app = App(0)
    app.MainLoop()


however, if I run the example with the latter code, as soon as the
mouse is over the render window, the app crashes. Why in the first case
does an application have to be created first (according to the documentation 
in
vtkRWI it does), while in the second case it appears that this is not 
possible
using a subclassed wx.App?

Dean