[Bf-committers] Simplifying node tree do_versions

[Ton Roosendaal]

Hi,

The macro is useful, I agree with that.

What we should keep in mind is that we should not abuse do-versions so much. It's currently being flooded with node patches, and in my perception most of these just aren't needed.

Design of .blend data can be done in a careful way, keeping for/backwards compatibility work, and just code functionality updates to be handled where this is being used.

The example I mailed yesterday (missing node->storage for translate node) is a good case, it's not depending on any versioning, it's just about upgrading the spec to always have such a struct. You can do that in direct-link, or better: in the code accessing the data.

My only objection is not the macro in itself, but by making it even easier to add version hacks. I would rather see this used with an absolute mininum.

So: before adding a versioning patch: consult at least some others to check if it's really needed, and if you can avoid it by smarter design.

-Ton-

------------------------------------------------------------------------
Ton Roosendaal  Blender Foundation   ton at blender.org    www.blender.org
Blender Institute   Entrepotdok 57A  1018AD Amsterdam   The Netherlands

On 8 Feb, 2013, at 10:38, Lukas Tönne wrote:

> I propose to introduce a C macro for use in readfile.c to clean up the
> frequent node tree do_versions mess. Currently whenever we need to
> iterate over all node trees in the library data we have to either make
> a number of repetitive bloated loops and/or use callbacks outside the
> actual do_versions function. Here's an example of one of my own fixes:
> 
> http://www.pasteall.org/39515/c
> 
> As you can see the loops in do_versions and the actual fix in the
> callback are spaced far apart and to figure out what is going on you
> have to jump around in this monster file quite a lot. Furthermore
> since we have node trees in 6 different ID data blocks currently it
> requires looping over all these blocks to iterate all potential node
> trees.
> 
> This macro would help make the code localized to just a few lines like
> most of the other do_versions code and keep things much more readable:
> 
> http://www.pasteall.org/39514/c
> 
> The macro automatically loops over all existing node trees with a
> single inner code block, so you don't have to repeat the same code
> over and over. If necessary it can be filtered easily by checking the
> node tree type. A minor overhead for looping over unused node trees
> would be added, but that should be nowhere near significant.
> 
> Using it for the example above boils it down to:
> 
> http://www.pasteall.org/39516/c
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