wxPython/demo/viewer.py

   1 #!/usr/bin/env python
   2
   3 """
   4     Run wxPython in a second thread.
   5
   6     Overview:
   7         Importing this module creates a second thread and starts
   8         wxPython in that thread.  Its single method,
   9         add_cone(), sends an event to the second thread
  10         telling it to create a VTK viewer window with a cone in
  11         it.
  12
  13         This module is meant to be imported into the standard
  14         Python interpreter.  It also works with Pythonwin.
  15         It doesn't seem to work with IDLE (on NT anyways).
  16         It should also work in a wxPython application.
  17
  18         Applications already running a wxPython app do not
  19         need to start a second thread.  In these cases,
  20         viewer creates the cone windows in the current
  21         thread.  You can test this by running shell.py
  22         that comes with wxPython, importing viewer and
  23         calling add_cone.
  24
  25     Usage:
  26         [user]$ python
  27         Python 1.5.2 (#1, Sep 17 1999, 20:15:36)  ...
  28         Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam
  29         >>> import viewer
  30         >>> viewer.add_cone() # pop up a cone window
  31         >>> a = 1
  32         1
  33         >>> viewer.add_cone() # create another cone window
  34
  35     Why would anyone do this?:
  36         When using wxPython, the call to app.Mainloop() takes over
  37         the thread from which it is called.  This presents a
  38         problem for applications that want to use the standard
  39         Python command line user interface, while occasionally
  40         creating a GUI window for viewing an image, plot, etc.
  41         One solution is to manage the GUI in a second thread.
  42
  43         wxPython does not behave well if windows are created in
  44         a thread other than the one where wxPython was originally
  45         imported. ( I assume importing wxPython initializes some
  46         info in the thread).  The current solution is to make the
  47         original import of wxPython in the second thread and then
  48         create all windows in that second thread.
  49
  50         Methods in the main thread can create a new window by issuing
  51         events to a "catcher" window in the second thread.  This
  52         catcher window has event handlers that actually create the
  53         new window.
  54 """
  55
  56 class viewer_thread:
  57     def start(self):
  58         """ start the GUI thread
  59         """
  60         import  time
  61         import  thread
  62         thread.start_new_thread(self.run, ())
  63
  64     def run(self):
  65         """
  66             Note that viewer_basices is first imported ***here***.
  67             This is the second thread.  viewer_basics imports
  68             wxPython.  if we imported it at
  69             the module level instead of in this function,
  70             the import would occur in the main thread and
  71             wxPython wouldn't run correctly in the second thread.
  72         """
  73         import  viewer_basics
  74
  75         try:
  76             self.app = viewer_basics.SecondThreadApp(0)
  77             self.app.MainLoop()
  78         except TypeError:
  79             self.app = None
  80
  81     def add_cone(self):
  82         """
  83             send an event to the catcher window in the
  84             other thread and tell it to create a cone window.
  85         """
  86         import  viewer_basics
  87
  88         if self.app:
  89             evt = viewer_basics.AddCone()
  90             viewer_basics.wxPostEvent(self.app.catcher, evt)
  91         else:
  92             viewer_basics.add_cone()
  93
  94 viewer = viewer_thread()
  95 viewer.start()
  96
  97 def add_cone():
  98     viewer.add_cone()
  99
 100