Line and LineSegment

[derekdreery]

The Line struct in kurbo is a straight line between 2 points. This is commonly called a LineSegment in other libraries (e.g. lyon), while the Line struct represents an infinite line.

Because kurbo doesn't have the concept of a lyon_geom::Line, it perhaps doesn't matter that there is this mismatch, but I just want to highlight it. Perhaps if something like lyon_geom::Line was added to kurbo in the future, it could be called InfiniteLine? Such a structure could be drawn (just draw the part of it that intersects with the viewport), and you could implement Shape for it (with some f64::INFINITYs).

Again I don't think it's worth or desirable to change the name for kurbo::Line, but I thought it was worth thinking about this mismatch.

[raphlinus]

I'm leaning toward not changing things, but it is an interesting question. I agree that more mathematically correct usage would be "line" for the infinite case and "line segment" for the bounded case. Actually if we're being really mathematically correct, it's a directed line segment, as the orientation is significant.

The other body of precedent includes SVG, which uses the word "line" for the same concept as in kurbo.

I'm not sure whether kurbo needs a type for the infinite line. It's not a proper shape (as it's not bounded), but I can see it maybe being useful for intersections.

[derekdreery]

I think sometimes it is useful to draw an infinite line. The way to draw it would be to clip it to whatever bounds the viewport was using.

[derekdreery]

I think the way to go naming-wise would be Line and InfiniteLine if there was a use-case.