Blender Git Loki

Merge branch 'master' into temp-gpencil-interpolate

Merge branch 'master' into greasepencil-object

Starting the unit tests

Tracking: Expose track average in the menu

Patch by Sebastian Koenig, thanks!

Tracking: Tweak order of pivot and proportional editing

Matches other editors. Was a mistake in the original code.

Patch by Sebastian Koenig, thanks!

Tracking: Fix wrong interpolation at the end of markers array

Tracking: Add interpolated accessor for markers

Allows to get marker position interpolated through out a gap.

Currently unused, but is covered with test. Aimed to be used for
track average operator.

Tracking: Implement tracks average operator

Average selected tracks into the new one. This can be used to improve
stability of tracking on blurry or non-very-sharp feature shapes.

Averaging happens for all position, pattern corners and search area.
Disabled markers do not take effect on averaging. Keyframed flag is
copied from source.

Gaps in the source tracks will be linearly interpolated, to reduce
result track jump. Note that this only applies to gaps "inbetween".
This means that if an input track doesn't have markers in the
beginning/end of it, there is nothing to interpolate with and the
result track will jump.

Available from the Track panel, under the Merge category.

Differential Revision: https://developer.blender.org/D6323

Tracking: Simplify transform code

Reduce amount of duplicated pointer offset logic: advance transform
data pointers deep in the loop rather than have offset duplicated in
the outer loop.

Array size calculation still has duplicated, but that is another story.

Tracking: Re-duplicate logic used to count and initialize data

Allows to easily implement more comprehensive checks about which
markers get added to the transformation context.

No user measurable changes are expected, purely house-keeping to
ease an upcoming development.

Tracking: Fix wrong projection for post-draw pass

Allows to draw proportional editing circle at a proper location.

Tracking: Implement proportional editing

Disclaimer: the user interface and interaction is not final. There
are known sharp corners, which are planned to be addressed while
the patch is being tested by people.

The idea is to avoid sudden jumps of track path when artists detects
track got slid away from the feature and one re-positions track back.
The implementation is based on a proportional editing, which allows
to control whether to transform single marker or whether to propagate
transform to markers from neighbour frames. The proportional editing
also allows to control propagation curve. The propagation will stop
at the end of tracked segment.

To test the new functionality:

1. Enable proportional editing
2. Enable "Connected Only". This is essential, as otherwise the new
functionality is not enabled.
3. Grab marker.

Open topics:
- Make the functionality more discoverable.
- Make visualization of how far propagation goes more clear.
- Make defaults more usable.

Technical TODO:
- Most likely CANCEL of the transform does not properly restore the
full state prior to the transform. This needs to be solved.

Differential Revision: https://developer.blender.org/D2771

Remove asserts in versioning and use non type specific reading

Fix errors in docstrings and make indentation consistent

Fix typo in error message

Use `int_from_py_int_or_double` function

Rename `check_ui_data_value` to `pyobject_can_convert_to_number`

Support booleans as inputs for UI data

Add NULL check in string default access

Add a `max_len` argument to RNA_property_string_get_default