[rfc] developer documentation on user interaction

[John Arbash Meinel]

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Vincent Ladeuil wrote:
>>>>>> "Gary" == Gary van der Merwe <garyvdm at gmail.com> writes:
> 
>     Gary> This seems to be quite an emotional discussion.... (/me treads carefully)
> 
> Sometimes things have to be said :-D
> 
> <snip/>
> 
>     Gary> No - I don't think that api stability was the reason
>     Gary> why we (luks) chose the subprocess design. The reason
>     Gary> why it was chosen was for maintaining ui interaction.
> 
> Nothing wrong with that, the problem is not trivial anyway.
> 
>     Gary> I personally feel that a single process, 2 threads, one
>     Gary> for ui, one for bzrlib, and some way for them to talk
>     Gary> (probably using qt event signals) would be much
>     Gary> better.
> 
> I'm pretty sure GTK provides ways for processes to exchange
> events, I'd be surprised if qbzr couldn't do the same.
> 
> Otherwise, you'll have to serialize/deserialize them in the
> pipes, since you're dealing with the same code on both sides, you
> shouldn't encounter nasty problems there.
> 

So interestingly, python2.6 provides a 'multiprocessing' module in the
standard lib, which is roughly equivalent to 'threading'.

In that you can say "multiprocessing.Process(python_func, *args)" and it
will spawn a subprocess that calls python_func with appropriate
arguments. It basically uses cPickle to marshal and unmarshal python
objects across the barrier.

I *don't* know how well it works with interactivity, or getting
progressive updates (can python_func be a generator rather than a plain
function? etc)

I would certainly consider switching the windows installers to python2.6
 for 2.1.0b1 and if it goes well, we could do the same for 2.0.1 or
whatever version comes out at a reasonable time.

I realize qbzr may want to keep backwards compatibility with python 2.4,
which is what bzrlib itself works to support. But it is an idea.


John
=:->

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