Update the Python API documentation about crashes with multi-threaded
code.
- Move the "threading gotcha" into a file of its own. That way it's
immediately clear from looking at the Gotcha table of contents that
threading is not supported.
- Simplify the example code, so that it doesn't access `bpy`.
Apparently the problem is much wider than just multi-threaded access
to `bpy`, and involves _all_ Python threads, regardless of what they
do / access.
- Add some more explanation and move some text from the bottom to the
top, so that the first-read part (when reading top to bottom) has
most of the information.
Pull Request: https://projects.blender.org/blender/blender/pulls/139279
Essentially, any operator modifying Blender data should enable this
`UNDO` option, else bad things (corruption, crashes...) are likely to
happen.
* Added a new Operator example to explain this topic.
* Updated some existing Operator examples that were not correct anymore.
* Added a new small section in the gotchas page linking to it.
* Added also short reminder about this in the `UNDO` 'tooltip'
description itself.
Related to #77557.
This PR:
* Splits the `Gotchas` page into several sub-sections. This was getting too big and hard to navigate.
* Adds some information regarding Python instances life-time of objects wrapping Blender internal data.
* Adds some information about usage of constructors and destructors for sub-classes of Blender-defined types.
Pull Request: https://projects.blender.org/blender/blender/pulls/129814
Blender may not apply certain UI data changes immediately when done via BPY.
This is a rather typical gotcha, better to have it documented.
Reviewed By: campbellbarton
Differential Revision: https://developer.blender.org/D15614
Especially with new undo/redo it is even less recommended to perform
complex operations in those callbacks, they should remain as fast and
localized as possible.
Also updated the section about undo/redo a bit.
As exposed in T62406, we can have some rare cases of crashes due to
memory re-allocation happening outside of expected scenarii.
Ideally this should be re-designed, but at least keep track of those
known exceptions to general rules...
* Added a TL;DR first paragraph summarizing that one shall not keep any
reference to Blender data when modifying its container.
* Added some info about fact that adding items to some data containers
(like Collection) can also invalidate existing items (due to array
re-allocation).
* Added a Do/Don't example which shows a crash after adding some items
to a collection.
Related to T61297.
Loop triangles are tessellated triangles create from polygons, for renderers
or exporters that need to match Blender's polygon tesselation exactly. These
are a read-only runtime cache.
Tessfaces are a legacy data structure from before Blender supported n-gons,
and were already mostly removed from the C code.
Details on porting code to loop triangles is in the release notes.
Differential Revision: https://developer.blender.org/D3539
- Blender/Python Addon Tutorial: a step by step guide on how to write an addon from scratch
- Blender/Python API Reference Usage: examples of how to use the API reference docs
Thanks to John Nyquist for editing these docs and giving feedback.
This also makes it clearer that the faces are for tessellated results only.
Added a section on the Gotcha's about upgrading scripts, the pros and cons of MeshTessFace/MeshPoly/BMFace.
and spesifically how to upgrade importers and exporters for 2.63+.
added python doc section on script performance and a note on relative file paths in the gotcha's page.
also added script for spell checking py comments.
