wxPython/demo/viewer.py

   1 #!/usr/bin/env python
   2 """
   3     Run wxPython in a second thread.
   4
   5     Overview:
   6         Importing this module creates a second thread and starts
   7         wxPython in that thread.  Its single method,
   8         add_cone(), sends an event to the second thread
   9         telling it to create a VTK viewer window with a cone in
  10         it.
  11
  12         This module is meant to be imported into the standard
  13         Python interpreter.  It also works with Pythonwin.
  14         It doesn't seem to work with IDLE (on NT anyways).
  15         It should also work in a wxPython application.
  16
  17         Applications already running a wxPython app do not
  18         need to start a second thread.  In these cases,
  19         viewer creates the cone windows in the current
  20         thread.  You can test this by running shell.py
  21         that comes with wxPython, importing viewer and
  22         calling add_cone.
  23
  24     Usage:
  25         [user]$ python
  26         Python 1.5.2 (#1, Sep 17 1999, 20:15:36)  ...
  27         Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam
  28         >>> import viewer
  29         >>> viewer.add_cone() # pop up a cone window
  30         >>> a = 1
  31         1
  32         >>> viewer.add_cone() # create another cone window
  33
  34     Why would anyone do this?:
  35         When using wxPython, the call to app.Mainloop() takes over
  36         the thread from which it is called.  This presents a
  37         problem for applications that want to use the standard
  38         Python command line user interface, while occasionaly
  39         creating a GUI window for viewing an image, plot, etc.
  40         One soultion is to mangage the GUI in a second thread.
  41
  42         wxPython does not behave well if windows are created in
  43         a thread other than the one where wxPython was originally
  44         imported. ( I assume importing wxPython initializes some
  45         info in the thread).  The current solution is to make the
  46         original import of wxPython in the second thread and then
  47         create all windows in that second thread.
  48
  49         Methods in the main thread can create a new window by issuing
  50         events to a "catcher" window in the second thread.  This
  51         catcher window has event handlers that actually create the
  52         new window.
  53 """
  54
  55 class viewer_thread:
  56     def start(self):
  57         """ start the GUI thread
  58         """
  59         import thread,time
  60         thread.start_new_thread(self.run, ())
  61
  62     def run(self):
  63         """
  64             Note that viewer_basices is first imported ***here***.
  65             This is the second thread.  viewer_basics imports
  66             wxPython.  if we imported it at
  67             the module level instead of in this function,
  68             the import would occur in the main thread and
  69             wxPython wouldn't run correctly in the second thread.
  70         """
  71         from viewer_basics import *
  72         try:
  73             self.app = SecondThreadApp(0)
  74             self.app.MainLoop()
  75         except TypeError:
  76             self.app = None
  77
  78     def add_cone(self):
  79         """
  80             send an event to the catcher window in the
  81             other thread and tell it to create a cone window.
  82         """
  83         import viewer_basics
  84         if self.app:
  85             evt = viewer_basics.AddCone()
  86             viewer_basics.wxPostEvent(self.app.catcher, evt)
  87         else:
  88             viewer_basics.add_cone()
  89
  90 viewer = viewer_thread()
  91 viewer.start()
  92
  93 def add_cone():
  94     viewer.add_cone()
  95
  96