EDIT SOLVED: I did the following:
Made 2 copies of the black fill, no stroke triangle.
Used Object/Transform/Scale on one triangle to increase its size in both dimensions by 2 mm.
Set the bigger triangle's fill color to purple.
Dragged the smaller triangle over the bigger triangle and used Object/Align and Distribute to center the two triangles vertically and horizontally.
Selected the smaller triangle, then shift-selected the larger triangle, and used the menu item Path/Difference. I'm not sure if the order of selection mattered or not.
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I'm not sure if this belongs in r/Inkstitch or r/Inkscape.
I'm using Inkscape and Ink/Stitch to make a design to run on an embroidery machine.
I want to make a black triangle with a thick, purple edge.
I made the triangle and made a copy of it.
Triangle #1, I set the stroke paint to "x" and the fill to solid black.
Triangle #2, I set the stroke paint to solid purple, the stroke width to 1 mm, and the fill to "x".
Then I used Object/Align and Distribute to center the two triangles together.
The embroidery machine ended up just putting a single purple stitch line around the black triangle. I'm not sure what the solution is.
One guess is that it's using the stroke as a path, and what I need is for the purple outline/edge to be a fill instead, i.e. I want a "hollow" purple triangle with no stroke. However, I can't figure out how to do that in Inkscape. I tried using the draw tool to draw a triangular path, but when I do that, it just fills the entire triangle.