DoEvents equiv?

[Mark Hammond]

Carlos Ribeiro wrote:

> At 22:58 09/05/01 +0000, Mark Hammond wrote:
> 
>> Carlos Ribeiro wrote:
>>
>>> Mark, don't you think that it would make sense for the Python 
>>> interpreter to have some option to call PumpMessages internally from 
>>> time to time? It's part of being a good citizen of Windowsland. I was 
>>> wondering if it is possible to make a call from inside the 
>>> interpreter, yielding control back to Windows periodically.
>>
>>
>> As I mentioned, it depends on the GUI system.  I dont know how Python 
>> could implement this so it works with MFC, Win32GUI, wxPython and 
>> Tkinter apps.
> 
> 
> I'm not an expert on this issue, 


But don't let that stop you :)


> but, as far as I know, it doesn't depend on the GUI system. 


It does.

> It's just a matter of calling PumpMessages, from the Win32 library. 


There is no such call in the Win32 library.

Each app provides its own event loop.  DoEvents/PumpMessages dispatches 
events waiting in the event queue.  Different apps have different 
requirements for their event queues.  For example, Tkinter has a very 
complex event loop, and it is almost certain that a simple event loop 
would not work for Tkinter.

> All Win32 applications should honor this call. 


What call?


> Mark, it's not lazyness. The problem is that you can't just put it in a 
> single line of code. You have to scatter calls to 
> pythoncom.PumpWaitingMessages all over the place, specially if you are 
> doing something more complex. And using threads just for this is 
> overkill. 


I disagree.  If you are writing a GUI app, you should design an 
architecture so that the GUI does not block for long periods of time.

What happens if during your PumpMessages() call, the user actually 
selects a different menu item, and recursively starts an operation?

> Also, note that this call is not available under Linux, so you 
> have to take this in account also (test the os, load pythoncom only on 
> Win32...).


So what do you suggest we use for Linux?  If we can not define a 
standard event loop for a Windows app, I doubt we will be able to for Linux.

If you really believe we can do this, submit some patches.

Mark.