When a paint stroke is executed instead of processed via the modal
handler, prior to this commit, the `paint_brush_update` function was
not called. This method handles initialization of some temporary stroke
data inside `UnifiedPaintSettings`, which is used by dyntopo when
performing edge collapse.
This had the result of causing a divide by 0 with certain uninitalized
settings when using a brush with dyntopo enabled and calling the
operator from the python API (e.g. from unit testing), resulting in
nonsensical deformations.
There are a number of weak points with the current design:
* This issue was only exposed because of the refactor to the
`UnifiedPaintSettings`, indicating that despite these values being
runtime-only, they were still persisted in some cases in .blend files
* The data stored as individual stroke steps is not sufficient to
reconstruct a paint stroke given a list of screen-space locations, and
this data is populated outside of the common `stroke` callbacks.
Both of the above issues are wider reaching than this PR is intended to
fix.
This commit ensures that `paint_brush_update` is called in the `exec`
codepath and updates the related test image.
Pull Request: https://projects.blender.org/blender/blender/pulls/141314
6fb90e5303