[Sugar-devel] [Physics Activity] Saving contraptions

[Gary C Martin]

Hi Asaf,

On 18 Jun 2009, at 02:42, Asaf Paris Mandoki wrote:

> I've been doing some research and I think that the easiest way to  
> save a world is by pickling. Pybox2d already supports it so it is  
> pretty straightforward. I think this should be implemented at the  
> level of Elements and not directly on the activity. Should I do it  
> in the modified elements we have inside the activity or should we  
> try to unify the different elements versions?

I guess working upstream would be best, is it a dead project now or do  
the original authors still have some interest? The Elements site did  
seem lacking in maintenance and love :-)

> I personally will prefer to unify the versions to get more benefit  
> from the work.

Yes, makes sense.

> We should take into account that after I finish with "world saving"  
> I will work on some new features for the activity that will require  
> adding features to elements.

Yes, I noticed the layers between gtk+, sugar stuff, elements,  
olpcgames, pygames was quite a nasty spaghetti stack to try and work/ 
look through and to know who could talk to what – found it pretty  
tough myself to reference/access to anything useful from the actual  
Activity code. Luckily I managed to re-work and trigger some pygame  
events created by the toolbox code for the things I needed to add / fix.

> There are other alternatives for world saving. An objection to  
> pickling is that is not human readable and we won't be able to edit  
> scenes with a text editor but I think that it's better if we add and  
> polish editing features directly in the activity. The odds that the  
> end user will try to edit a scene with a text editor are minimal.

I can't imagine 98% of users ever considering manual editing, though  
one thing to keep in mind is that pickling is Python specific, I guess  
there could be a vague possibility of wanting to open a file with  
another language (json implementations are widely available). But if  
you have a pickling solution, I would not let that stand in you way!  
We can't future proof everything :-)

Any other progress/ideas? Physics seems to have been quite a hit a  
LinuxTag :-)

Regards,
--Gary