[SciPy-dev] gui_thread and chaco under Linux

Pearu Peterson pearu at scipy.org
Wed Oct 8 06:56:07 CDT 2003

Hi Prabhu,

On Tue, 7 Oct 2003, Prabhu Ramachandran wrote:

> Well, gui_thread does work under Linux.  For example, this works for
> me:
> In [1]: import gui_thread
> In [2]: gui_thread.start()
> <Importing wxPython... i done.>
> >>>
> In [3]: import scipy.plt as plt
> In [4]: p = plt.plot([1,4,9])
> I think its just that wxplt is not using gui_thread and is currently
> pure wxPython code.

Thank you for the clarification! I must admit that at first I really
didn't understand the code in gui_thread (now I do, after re-implementing
it almost from a scratch;-).

>  As you have rightly discovered the way to
> chaco-on-interpreter-heaven is to call all wxPython related functions
> from another thread and this thread must be the first to import
> wxPython.  To use gui_thread you need to 'register' a class with it.
> gui_thread then returns a massaged class wraps around the actual class
> that the actual functions are called in the right thread.  It also
> tries to handle attribute access safely.  However, this is from memory
> having hacked on gui_thread about two years ago and a few things might
> have changed.  Anyway, the way to register a class with gui_thread is
> to do the following:
> wrapped_class = gui_thread.register(some_wx_python_class)
> Then you create wrapped_class instances as you would create
> some_wx_python_class and it should work (in theory).

This will not work for chaco anymore because chaco executes wxPython 
functions during chaco.wxplt import. 

>  I can't test this because I cannot run chaco anymore.  kiva no longer
> builds under gcc 2.95.4. :(

Yes. In fact, this triggered me to upgrade gcc on my debian system.
It turned out to be quite painless, now I have
  gcc-2.95  gcc-3.2   gcc-3.3
nicely co-existing on my system. 
You could try the same ^K ;-)

> Admittedly, the gui_thread approach is a hack and has limitations but
> it used to work pretty OK.  Eric was talking about a better approach
> that IIRC is similar to your approach (1).  As you notice its a
> non-trivial job and AFAIK no one has yet had a stab at it.

I took this challenge and here are intermediate results:

>>> from parallel_exec import ParallelExec
>>> pexec=ParallelExec() # create wxPython thread
>>> pexec('import wxPython.wx')
>>> pexec('from wrap_wx import ParallelExec_wxApp;app=ParallelExec_wxApp()')
>>> pexec('app.run()')
# Now calling app will execute commands in wxPython thread:
>>> app('from chaco.wxplt import *')
>>> app('plot([1,2])') # creates a plot [1,2]
>>> app('figure()')    # opens new empty window
>>> app('plot([5,2])') # creates a plot [5,2] in new window
>>> app.shutdown()

that is, I can already use chaco from my Linux prompt! And I have made no 
changes to chaco for that. The next step is to make

>>> from chaco.wxplt import *
>>> plot([1,2])



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