novaBBS - comp.fonts - Truetype and Opentype outline restrictions?

Truetype and Opentype outline restrictions?

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https://www.novabbs.com/devel/article-flat.php?id=13&group=comp.fonts#13

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Subject: Truetype and Opentype outline restrictions?
From: kevinrog...@invisionapp.com (Kevin Rogovin)
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by: Kevin Rogovin - Tue, 2 Nov 2021 10:10 UTC

Hi,

I am thinking about writing (another) GPU glyph renderer. My usual jazz is that I do not make any assumptions on the nature of the contours of a scalable glyph: I just treat it as an arbitrary path fill. However, recently I have (another) glyph rendering idea and it requires some properties on the outlines (or rather without various restrictions, the complexity gets higher). With that in mind, my questions:

1. Is it legal for a contour of a font to self intersect? I.e. a single contour intersects itself?
2. If two contours intersect, are they guaranteed to be oriented the same way? i.e. they won't "cancel" their winding over the region of their interior?

I ask these questions because one part of the spec talks about computing a winding number and using the non-zero fill rule and another part talks about that contour orientation is that clockwise oriented contours encode empty space and counter-clockwise encode solid space.

If the contour's are somewhat separable, i.e. question 2, some issues go away...

You might have mail.

devel / comp.fonts / Truetype and Opentype outline restrictions?

Subject	Author
Truetype and Opentype outline restrictions?	Kevin Rogovin