[IPython-dev] [Enthought-Dev] Ctypes based prototype of PyOS_InputHook for wx 2.8 and 2.9

Development matplotlib-devel
1

The chunkiness probably comes from the fact that inputhook_wx is called repeatedly. This is different from how PyOS_InputHook is being used in Tkinter, PyGTK, and the Mac OS X backend.

Schematically, this is how the Tkinter/PyGTK/MacOSX event loops work:

1) PyOS_InputHook is called when Python is waiting for the user to type in the next Python command.

2) The hook function sets up the event loop such that stdin is being monitored while the event loop is running.

3) The hook function then starts the event loop.

4) When input is available on stdin, the hook function exits the event loop, and returns.

This is how the proposed Wx event loop currently works:

1) PyOS_InputHook is called when Python is waiting for the user to type in the next Python command.

2) The hook function processes whatever events are available at the time.

3) The hook function returns.

4) If still no input is available on stdin, Python calls the hook function again via PyOS_InputHook after a timeout.

I believe the timeout is 0.1 seconds by default. However, Python may not call PyOS_InputHook repeatedly at all; this depends on which Python version is being used, and the version of the readline library. In some configurations (particularly on Windows), PyOS_InputHook is called only once, so wx will freeze between Python commands.

I am not familiar with wx, but there hopefully there is some way to monitor stdin while the event loop is running?

--Michiel.

···

--- On Thu, 7/16/09, Brian Granger <ellisonbg.net@...149...> wrote:

From: Brian Granger <ellisonbg.net@...149...>
Subject: Re: [matplotlib-devel] [IPython-dev] [Enthought-Dev] Ctypes based prototype of PyOS_InputHook for wx 2.8 and 2.9
To: "Robert Kern" <rkern@...492...>
Cc: enthought-dev@...492..., "matplotlib development list" <matplotlib-devel@lists.sourceforge.net>, "IPython Development list" <ipython-dev@...741.....>
Date: Thursday, July 16, 2009, 6:57 PM
Robert,

Thanks for testing this so quickly. Performance is one of
the big issues that I am concerned about. I will work on a
Cython based version to see if that solves the problem.

Cheers,

Brian

Works for me with wx 2.8.8.1 on OS X 10.5 and
Chaco. Pan and zoom

interactions are substantially chunky, though. I do not see
such

chunkiness with -wthread. It would be worth exploring a
Cython

alternative to see if it is just ctypes and general Python
overhead to

blame.

--

Robert Kern

"I have come to believe that the whole world is an
enigma, a harmless

enigma that is made terrible by our own mad attempt to
interpret it as

though it had an underlying truth."

-- Umberto Eco

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Michiel,

Thanks for the reply, this will help us to find a better approach. According to one of the wx devs, Robin Dunn, wx currently does not have the ability to monitor stdin in its even loop without polling. I guess there is a GSoC project to add this capability, but it is not there yet. Any thoughts on how this could be done without monitoring stdin. I will give the polling stdin approach a try though.

Cheers,

Brian

···

The chunkiness probably comes from the fact that inputhook_wx is called repeatedly. This is different from how PyOS_InputHook is being used in Tkinter, PyGTK, and the Mac OS X backend.

Schematically, this is how the Tkinter/PyGTK/MacOSX event loops work:

  1. PyOS_InputHook is called when Python is waiting for the user to type in the next Python command.

  2. The hook function sets up the event loop such that stdin is being monitored while the event loop is running.

  3. The hook function then starts the event loop.

  4. When input is available on stdin, the hook function exits the event loop, and returns.

This is how the proposed Wx event loop currently works:

  1. PyOS_InputHook is called when Python is waiting for the user to type in the next Python command.

  2. The hook function processes whatever events are available at the time.

  3. The hook function returns.

  4. If still no input is available on stdin, Python calls the hook function again via PyOS_InputHook after a timeout.

I believe the timeout is 0.1 seconds by default. However, Python may not call PyOS_InputHook repeatedly at all; this depends on which Python version is being used, and the version of the readline library. In some configurations (particularly on Windows), PyOS_InputHook is called only once, so wx will freeze between Python commands.

I am not familiar with wx, but there hopefully there is some way to monitor stdin while the event loop is running?

–Michiel.

— On Thu, 7/16/09, Brian Granger <ellisonbg.net@gmail.com> wrote:

From: Brian Granger <ellisonbg.net@gmail.com>

Subject: Re: [matplotlib-devel] [IPython-dev] [Enthought-Dev] Ctypes based prototype of PyOS_InputHook for wx 2.8 and 2.9

To: “Robert Kern” <rkern@…492…>

Cc: enthought-dev@…492…, “matplotlib development list” matplotlib-devel@lists.sourceforge.net, “IPython Development list” <ipython-dev@…336…>

Date: Thursday, July 16, 2009, 6:57 PM

Robert,

Thanks for testing this so quickly. Performance is one of

the big issues that I am concerned about. I will work on a

Cython based version to see if that solves the problem.

Cheers,

Brian

Works for me with wx 2.8.8.1 on OS X 10.5 and

Chaco. Pan and zoom

interactions are substantially chunky, though. I do not see

such

chunkiness with -wthread. It would be worth exploring a

Cython

alternative to see if it is just ctypes and general Python

overhead to

blame.

–

Robert Kern

"I have come to believe that the whole world is an

enigma, a harmless

enigma that is made terrible by our own mad attempt to

interpret it as

though it had an underlying truth."

– Umberto Eco

IPython-dev mailing list

IPython-dev@…336…

http://mail.scipy.org/mailman/listinfo/ipython-dev

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limited time,

vendors submitting new applications to BlackBerry App

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the opportunity to enter the BlackBerry Developer

Challenge. See full prize

details at: http://p.sf.net/sfu/Challenge

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