Fills a path with a shading pattern.
void FillPathWithShading(PathView path, FillRule rule, in DisplayShading shading)
The path in user space under the current transform, exactly as for FillPath(PathView, FillRule, in DisplayColor).
The rule that decides the inside (§8.5.3.3.2, §8.5.3.3.3).
The pattern's shading, in pattern space (Matrix), with its Background.
ISO 32000-2 §8.7.4.1, Table 75, and §8.7.4.3, Table 77: inside the path (and the clip), the Background, when present, fills the points outside the shading's bounds, then the shading paints the points it defines within its BBox.