7f1a8f9956
While having negative values in the data itself seems fine (at least
there is nothing in the design forbidding it, and it was also allowed in
GPv2 data), drawing code should only accept positive values, and clamp
negative ones to zero:
* It matches GPv2 behavior.
* Drawing code uses negative values as some sort of 'flag' for
rounded tips of strokes.
Note: This is a follow-up of !120840.
Co-authored-by: Falk David <falk@blender.org>
Pull Request: https://projects.blender.org/blender/blender/pulls/122173