[Bf-committers] Reference counting, deleting data and fake users

[Bassam Kurdali]

+1
On Fri, 2012-03-16 at 17:14 -0700, Nathan Vegdahl wrote:
> Upon further consideration, I've changed my mind: I think we should go
> back to actions having fake users by default.  For my particular
> use-cases it's fine (and convenient) for actions to not have fake
> users, but as is clear from the blenderartists.org thread, there are
> other use-cases that make this a problem.
> 
> It's very easy to simply forget to set an action to have a fake user,
> and the result of that easy mistake can be significant data loss.  It
> is better for people such as myself to be inconvenienced with dangling
> actions than it is for other people to suffer significant data loss
> from a simple mistake.  Easy-to-commit-user-error should never, ever
> result in significant data loss, and yet that is the situation we have
> here.  That is more important than being consistent.
> 
> Further discussion about how data should be handled in Blender is
> still valuable, but for now let's at least change the default back to
> actions having fake users.
> 
> --Nathan
> 
> 
> On Fri, Mar 16, 2012 at 2:49 PM, Juha Mäki-Kanto <kiskosika at gmail.com> wrote:
> > Would it be difficult to add a mode of saving which would not drop the
> > unreferenced data? This would allow the user to decide when the garbage
> > collection is done so you'd know when you have to worry about things going
> > missing. Additionally a way to list data to be deleted might be nice.
> >
> > 16. maaliskuuta 2012 18.43 Alexander Zubov <a_zubov11 at yahoo.com> kirjoitti:
> >
> >> I think the easiest solution to this issue would be adding a prompt
> >> message on exit "You have unsaved Actions. Would you like exit anyway?" or
> >> something on that nature. This way user can go back and press F button on
> >> the Actions he wants to keep.
> >>
> >> --- On Fri, 3/16/12, Bassam Kurdali <bassam at urchn.org> wrote:
> >>
> >> > From: Bassam Kurdali <bassam at urchn.org>
> >> > Subject: Re: [Bf-committers] Reference counting, deleting data and fake
> >> users
> >> > To: "bf-blender developers" <bf-committers at blender.org>
> >> > Date: Friday, March 16, 2012, 11:21 AM
> >> > big -1
> >> > I don't think it's simple, and I'm not sure it's even
> >> > desirable;
> >> > changing behavior like this, when the original complaint was
> >> > that
> >> > actions not getting fake users by default, going into a
> >> > massive change
> >> > of design.
> >> > there are so many things in blender that need big redesign,
> >> > like the
> >> > dependency graph and library linking/refrencing, that going
> >> > into major
> >> > restructuring of things that *aren't broken* just seem like
> >> > a ridiculous
> >> > thing. Especially as this would be at least a highly
> >> > controversial
> >> > change.
> >> > So if you're looking at a big architectural/ design/ under
> >> > the hood
> >> > challenge, wouldn't you please fix the depgraph first ;) ?
> >> >
> >> > > I don't see any big technical difficulty personally. We
> >> > can just
> >> > > modify the refcount increasing/decreasing function to
> >> > use an observer
> >> > > pattern scheme and if a datablock is deleted simply
> >> > inform the
> >> > > observers of the deletion (And the human user if the
> >> > datablock has
> >> > > more users). It will require some interface for the
> >> > observers too but
> >> > > I don't think it's an unsurpassable challenge, even in
> >> > C :p. The
> >> > > memory footprint of datablocks will slightly increase
> >> > but it's a
> >> > > negligible amount of data compared to meshes etc.
> >> > > _______________________________________________
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> >> >
> >> >
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