[Bf-python] Generate NLA Strips with Python

[Roland Hess]

Hi all. In order for my BlenderPeople project to continue, I needed 
to be able to generate NLA strips from existing actions via Python. I 
just finished testing a compiled build with that functionality. I'll 
give you an overview and post a link to the patch file. I'm not sure 
what the standards/best practices are for actually writing this 
stuff, so anything that's bad, well, feel free to send me back to the 
drawing board.

Method of Attack:
Trying to keep the Python layer as thin as possible, I wrote the main 
NLA strip creation function directly into editnla.c in the blender 
/src directory. The new function is public and accepts inputs of 
armature and action name, start and end frames, and a repeat value. 
If the armature name and action name exist, an NLA strip is created 
with the specified values. I put the functionality in the editnla.c 
section so that other Blender functions can internally call it and 
send it generic values for NLA creation, if they should ever need to.

The Python portion only defines the function for scripting access, 
does some validity checking on user inputs, then calls the function 
found in editnla.c.

As I wasn't sure if an all new Python module called NLA would 
necessitate changes in the makefiles (which I have no clue about), I 
rolled this into the Armature module. The function is accessed from 
Python as:

Armature.AddNLA(ArmatureName,ActionName,startframe,endframe,repeat)

Things to consider:
I believe it would be beneficial to have two different functions: the 
one I have written in editnla.c and a new one that accepts a link to 
an armature object instead of an armature name.  It might also be 
useful to split off two lookup functions that return both armature 
and action object pointers given the respective names.

As far as editing already existing NLA strips, this may not be 
possible. NLA strips are not currently named. Within the NLA source, 
they are only accessed sequentially when generating animation, and by 
proximity to the mouse pointer when editing, so there is no way I can 
think of to direct changes to a particular strip, unless you went 
through the list of all strips, checking for armature/action name and 
start/end frame characteristics. Bleh. Deleting strips also faces the 
same problem.

As there is really only a single function, and it applies to armature 
objects, is there any reason to split this off into its own NLA 
module as opposed to piggybacking on the Armature module?

Patch:

http://66.134.133.114/patch.txt

In case you just want to look at the code, my new stuff is:

in editnla.c: add_nlablock_generic(args)
in armature.c: M_Armature_AddNLA(args)

Thoughts? Anyone else want to test/fix/beautify/advise about this code?
-- 
Roland Hess (harkyman)
Digital Prepress/Network Administrator
Reed & Witting Company