Support for Get/Set callbacks in bpy.props

This patch adds support in bpy.props for getter/setter callback functions. We already have update callbacks, but generic get/set functions can come in handy in some cases where the functionality is too complex to use a single value.

The current C callback functions are too simple allow a straightforward implementation, in particular they don't receive the PropertyRNA pointer itself as an argument, which means the callback cannot directly access the PropertyRNA's py_data pointers which store the python function objects. For this reason a second runtime variant of these callbacks has been added. It is only used for runtime callbacks and not in makesrna, but otherwise works the same way.

A few possible improvements:

* BPy_EnumProperty: Could use generic property py_data slot for the enum item callback. Would be one unused pointer for non-enum properties, but a bit simpler.

* BPy_EnumProperty: Integrate enum item function argument check into general bpy_prop_callback_check.

* enum get/set callbacks only work with integer values for now. Using string identifiers would be better, for that the extended callback variants must be modified for runtime enum callbacks. No access to the items list in get/set itself (no context).

[lukas.toenne1, 2013-01-04 18:46:32]

Here is a small test file:

http://www.pasteall.org/blend/18621

Just run the test.py script from blender editor. It creates a number of
properties in Object using get/set functions and prints values.

[ideasman42, 2013-01-05 13:32:07]

LGTM, besides some minor suggestions

https://codereview.appspot.com/7027056/diff/1/source/blender/makesrna/intern/...
File source/blender/makesrna/intern/rna_access.c (right):

https://codereview.appspot.com/7027056/diff/1/source/blender/makesrna/intern/...
source/blender/makesrna/intern/rna_access.c:995: +		*softmin = MAX2(*softmin,
hardmin);
picky, preference for min_ii, max_ii

https://codereview.appspot.com/7027056/diff/1/source/blender/makesrna/intern/...
source/blender/makesrna/intern/rna_access.c:995: +		*softmin = MAX2(*softmin,
hardmin);
picky, preference for min_ff, max_ff

https://codereview.appspot.com/7027056/diff/1/source/blender/python/intern/bp...
File source/blender/python/intern/bpy_props.c (right):

https://codereview.appspot.com/7027056/diff/1/source/blender/python/intern/bp...
source/blender/python/intern/bpy_props.c:267: value = 0.0f;
float, should be true/false

https://codereview.appspot.com/7027056/diff/1/source/blender/python/intern/bp...
source/blender/python/intern/bpy_props.c:364: PyObject *py_seq =
PySequence_Fast(ret, "the return value must be a sequence");
Think it'd be better to use: PyC_AsArray here

https://codereview.appspot.com/7027056/diff/1/source/blender/python/intern/bp...
source/blender/python/intern/bpy_props.c:577: PyObject *py_seq =
PySequence_Fast(ret, "the return value must be a sequence");
Think it'd be better to use: PyC_AsArray here

https://codereview.appspot.com/7027056/diff/1/source/blender/python/intern/bp...
source/blender/python/intern/bpy_props.c:639: py_values = PyTuple_New(len);
Not so important but could have a util function - PyC_ToArray that works like
PyC_AsArray.

same goes for other types here.

https://codereview.appspot.com/7027056/diff/1/source/blender/python/intern/bp...
source/blender/python/intern/bpy_props.c:789: else {
Think it'd be better to use: PyC_AsArray here

https://codereview.appspot.com/7027056/diff/1/source/blender/python/intern/bp...
source/blender/python/intern/bpy_props.c:989: PyTuple_SET_ITEM(args, 1,
PyUnicode_FromString(value));
should error check that PyUnicode_FromString() isnt failing.

[lukas.toenne1, 2013-01-05 14:39:45]

https://codereview.appspot.com/7027056/diff/1/source/blender/makesrna/intern/...
File source/blender/makesrna/intern/rna_access.c (right):

https://codereview.appspot.com/7027056/diff/1/source/blender/makesrna/intern/...
source/blender/makesrna/intern/rna_access.c:995: *softmin = MAX2(*softmin,
hardmin);
On 2013/01/05 13:32:07, ideasman42 wrote:
> picky, preference for min_ii, max_ii

I basically just copy/pasted this from the case above, guess that should be
changed too then.

https://codereview.appspot.com/7027056/diff/1/source/blender/python/intern/bp...
File source/blender/python/intern/bpy_props.c (right):

https://codereview.appspot.com/7027056/diff/1/source/blender/python/intern/bp...
source/blender/python/intern/bpy_props.c:267: value = 0.0f;
On 2013/01/05 13:32:07, ideasman42 wrote:
> float, should be true/false

Done.

https://codereview.appspot.com/7027056/diff/1/source/blender/python/intern/bp...
source/blender/python/intern/bpy_props.c:364: PyObject *py_seq =
PySequence_Fast(ret, "the return value must be a sequence");
On 2013/01/05 13:32:07, ideasman42 wrote:
> Think it'd be better to use: PyC_AsArray here

Done.

https://codereview.appspot.com/7027056/diff/1/source/blender/python/intern/bp...
source/blender/python/intern/bpy_props.c:577: PyObject *py_seq =
PySequence_Fast(ret, "the return value must be a sequence");
On 2013/01/05 13:32:07, ideasman42 wrote:
> Think it'd be better to use: PyC_AsArray here

Done.

https://codereview.appspot.com/7027056/diff/1/source/blender/python/intern/bp...
source/blender/python/intern/bpy_props.c:639: py_values = PyTuple_New(len);
On 2013/01/05 13:32:07, ideasman42 wrote:
> Not so important but could have a util function - PyC_ToArray that works like
> PyC_AsArray.
> 
> same goes for other types here.

Done.

https://codereview.appspot.com/7027056/diff/1/source/blender/python/intern/bp...
source/blender/python/intern/bpy_props.c:789: else {
On 2013/01/05 13:32:07, ideasman42 wrote:
> Think it'd be better to use: PyC_AsArray here

Done.

https://codereview.appspot.com/7027056/diff/1/source/blender/python/intern/bp...
source/blender/python/intern/bpy_props.c:989: PyTuple_SET_ITEM(args, 1,
PyUnicode_FromString(value));
On 2013/01/05 13:32:07, ideasman42 wrote:
> should error check that PyUnicode_FromString() isnt failing.

Done.