[feature request] anchors for line's coordinates + length and area

[Akilon27]

It would be interesting to have anchors to the coordinates that makes the line up.

I know it was already proposed in #640 and closed as not planned after the author refused the proposed syntax (which was very reasonable). Could you add it ?

The proposed syntax was : for a line name "line", "line.pt-1" for the first point and so on.

The advantages I see :

• the line function resolves coordinates so no need to resolve them again if they are necessary elsewhere
• it add the possibility to compute the line length (and if close: true, the area with the shoelace formula)

In the angle function, the measure can be accessed if a function is given to the label which is awesome, could the same be implemented for the length and area ?

Thanks

[johannes-wolf]

In the angle function, the measure can be accessed if a function is given to the label which is awesome, could the same be implemented for the length and area ?

A function to get the length/area as a callback to which parameter? Do you have an example of your possible use?

[Akilon27]

My idea was they could be given to a label parameter... I don't think a number can be saved in a string like "line.area".
For an angle, you can do angle.angle(a,b,c, label:x=>$#x/1deg °$).
I was thinking they could both be used the same : line(a,b,c,d, close:true, name: "line", label: (x,y) => $P("ABCD") = #x "cm" \ A("ABCD"=#y "cm"^2$) for exemple with the label at the centroid or another anchor (maybe relative to "line.pt-1" or something).

I hope I expressed my idea clearly.