To do a strictly correct approach, that may be right.
However looking at the workaround I’ve done above, an idea for a much simpler approach occurs to me.
(it may only appear in Gerber files, but that’s probably tolerable) When you select Segment Hatch mode, add field to allow the user to select a simple skip-value.
1:1 plots every line, for solid segments
1:2 plots every second segment line, for 50% hatch
1:3 plots every 3rd segment line, for 33% hatch
1:4 plots every 4th segment line, for 25% hatch You could also allow allow define of that Hatch line width, (<= outline width) to fine-tune the grid.
(that’s what I did in Gerber file)
So that’s two simple numbers the user enters, and the algorithm is a very simple skip-lines one, nothing complex needed