[Bf-committers] [Bf-blender-cvs] SVN commit: /data/svn/bf-blender [37260] trunk/blender/source/blender: Support for update callbacks in python defined RNA properties as discussed last meeting .

[Matt Ebb]

Hi Campbell, I've been looking into this feature a bit further and tried to
use it in my scripts, and it's not quite as useful as I'd expected.

The main reason for this is the limited access to other blender data - I can
access self (the property itself), and I can access context, but there's not
a lot I can do with that. For example if I'm adding an update function to a
material property, there's not really any easy way of finding the material
that the property is attached to, via context. I've noticed this for the
dynamic enums too, just self and context really isn't enough to be useful.

What would be really handy is if there was something similar to RNA usage in
C, where you have access to not only the pointer itself, but also the data
that contains that pointer (ptr->data) and also the top level ID block
(ptr->id.data). This would be much more practical for update functions,
enabling the sort of things that are commonly done in the C RNA definitions.

One possibility could be to pass those pointers as arguments to the update
function, but I also wonder if it would it be possible to expose the
ptr->data and ptr->id.data as children of the python RNA property object
itself? Perhaps in a similar way to how an RNA property contains flags like
read only and hidden, its type and subtype, units, etc. Then in an update
function you could use self.id_data or something like that. I have no idea
about the practicalities of how this could work in python though, it's just
an idea.

Regardless, having access to data such as this, however it may be
implemented, would be very useful!

cheers

Matt


On Sat, Jun 25, 2011 at 12:09 PM, Campbell Barton <ideasman42 at gmail.com>wrote:

> @Matt, yes it does use the internal RNA update function, it also
> disables the readonly state (if set) for the duration of the update
> call.
>
> Agree the animation system should be calling update functions though I
> think we need to have it optimized for arrays.
> If you have 20 layers all animated, ideally wouldn't call update 20
> times for example.
>
> Slightly related is the layer animation bug, where setting the layer
> doesn't always work right because blender ensures at any point in time
> at least 1 layer is enabled.
>
> IMHO it's worth looking into collecting RNA writes per datablock and
> assigning arrays so the 'set' functions get the new array as a single
> assignment (currently each index is assigned individually).
> With this we could run each properties update function once too.
>
> - Campbell
>
> On Sat, Jun 25, 2011 at 1:20 AM, Daniel Salazar - 3Developer.com
> <zanqdo at gmail.com> wrote:
> > Indeed it's weird.. see this example with a driver based on
> > scene.frame_current. It will not update on frame change but it can be
> > tricked to do so by adding a variable pointing to an object (even to
> > itself) with an object level property animated. In this case I
> > inserted a keyframe on bounding box display type! :p after that it
> > will correctly update on frame change.. even if the variable isn't
> > even used in the expression
> >
> > http://www.pasteall.org/blend/7167
> >
> > what's going on?
> >
> > cheers to you two!
> >
> > Daniel Salazar
> > 3Developer.com
> >
> >
> >
> > On Fri, Jun 24, 2011 at 7:06 PM, Matt Ebb <matt at mke3.net> wrote:
> >> On Tue, Jun 7, 2011 at 3:50 AM, Campbell Barton <ideasman42 at gmail.com
> >wrote:
> >>
> >>> Revision: 37260
> >>>
> >>>
> http://projects.blender.org/scm/viewvc.php?view=rev&root=bf-blender&revision=37260
> >>> Author:   campbellbarton
> >>> Date:     2011-06-06 17:50:20 +0000 (Mon, 06 Jun 2011)
> >>> Log Message:
> >>> -----------
> >>> Support for update callbacks in python defined RNA properties as
> discussed
> >>> last meeting.
> >>> This means script authors can perform actions using these callbacks
> rather
> >>> then on drawing which puts blender in a readonly state.
> >>
> >>
> >> Late reply, I'm just getting some time to look into editing scripts to
> use
> >> this and wanted to say thanks for this Campbell, it's great. Just to
> >> clarify, is this implemented as a proper RNA update function which will
> act
> >> exactly like any other C-defined ones? If so, that's great, but useful
> >> either way.
> >>
> >> Probably worthwhile bringing up this issue again too (certain rna
> properties
> >> not running update functions in animation system), since it may be
> affected:
> >>
> http://lists.blender.org/pipermail/bf-committers/2010-November/029482.html
> >>
> >> cheers,
> >>
> >> Matt
> >> _______________________________________________
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>
>
>
> --
> - Campbell
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