wxPython/demo/viewer.py

   1 #!/usr/bin/env python
   2 #
   3 # 11/15/2003 - Jeff Grimmett (grimmtooth@softhome.net)
   4 #
   5 # o Updated for wx namespace
   6 #
   7
   8 """
   9     Run wxPython in a second thread.
  10
  11     Overview:
  12         Importing this module creates a second thread and starts
  13         wxPython in that thread.  Its single method,
  14         add_cone(), sends an event to the second thread
  15         telling it to create a VTK viewer window with a cone in
  16         it.
  17
  18         This module is meant to be imported into the standard
  19         Python interpreter.  It also works with Pythonwin.
  20         It doesn't seem to work with IDLE (on NT anyways).
  21         It should also work in a wxPython application.
  22
  23         Applications already running a wxPython app do not
  24         need to start a second thread.  In these cases,
  25         viewer creates the cone windows in the current
  26         thread.  You can test this by running shell.py
  27         that comes with wxPython, importing viewer and
  28         calling add_cone.
  29
  30     Usage:
  31         [user]$ python
  32         Python 1.5.2 (#1, Sep 17 1999, 20:15:36)  ...
  33         Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam
  34         >>> import viewer
  35         >>> viewer.add_cone() # pop up a cone window
  36         >>> a = 1
  37         1
  38         >>> viewer.add_cone() # create another cone window
  39
  40     Why would anyone do this?:
  41         When using wxPython, the call to app.Mainloop() takes over
  42         the thread from which it is called.  This presents a
  43         problem for applications that want to use the standard
  44         Python command line user interface, while occasionally
  45         creating a GUI window for viewing an image, plot, etc.
  46         One solution is to manage the GUI in a second thread.
  47
  48         wxPython does not behave well if windows are created in
  49         a thread other than the one where wxPython was originally
  50         imported. ( I assume importing wxPython initializes some
  51         info in the thread).  The current solution is to make the
  52         original import of wxPython in the second thread and then
  53         create all windows in that second thread.
  54
  55         Methods in the main thread can create a new window by issuing
  56         events to a "catcher" window in the second thread.  This
  57         catcher window has event handlers that actually create the
  58         new window.
  59 """
  60
  61 class viewer_thread:
  62     def start(self):
  63         """ start the GUI thread
  64         """
  65         import  time
  66         import  thread
  67         thread.start_new_thread(self.run, ())
  68
  69     def run(self):
  70         """
  71             Note that viewer_basices is first imported ***here***.
  72             This is the second thread.  viewer_basics imports
  73             wxPython.  if we imported it at
  74             the module level instead of in this function,
  75             the import would occur in the main thread and
  76             wxPython wouldn't run correctly in the second thread.
  77         """
  78         import  viewer_basics
  79
  80         try:
  81             self.app = viewer_basics.SecondThreadApp(0)
  82             self.app.MainLoop()
  83         except TypeError:
  84             self.app = None
  85
  86     def add_cone(self):
  87         """
  88             send an event to the catcher window in the
  89             other thread and tell it to create a cone window.
  90         """
  91         import  viewer_basics
  92
  93         if self.app:
  94             evt = viewer_basics.AddCone()
  95             viewer_basics.wxPostEvent(self.app.catcher, evt)
  96         else:
  97             viewer_basics.add_cone()
  98
  99 viewer = viewer_thread()
 100 viewer.start()
 101
 102 def add_cone():
 103     viewer.add_cone()
 104
 105