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

[patrick boelens]

Agreed. The fake-user system is confusing to a lot of people regardless 
of the default, so might as well make the default a safe one.
As long
 as an action (or any other datablock for that matter, but that's 
probably a whole nother discussion) isn't explicitly deleted, most users
 would probably expect it to be there the next time they load Blender.

-Patrick

> From: bassam at urchn.org
> To: bf-committers at blender.org
> Date: Fri, 16 Mar 2012 21:47:44 -0400
> Subject: Re: [Bf-committers] Reference counting, deleting data and fake users
> 
> +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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