Why does fletcher's enclose option not enclose tightly in this figure?

[Paul744]

The following Typst fletcher code

#set page(
  width: auto,
  height: auto,
  margin: 2mm,
)

#import "@preview/fletcher:0.5.8" as fletcher: diagram, node, edge, cetz
#import fletcher.shapes: circle, pill, diamond, triangle

#diagram(
  debug: 3,
  node-shape: circle,
  node-outset: 0mm,
  node-fill: none,
  node-stroke: black,
  axes: (ltr, btt),
  let inn-dist = 1.8,
  let h-dist = 4.5,
  let v-dist = 2.5,
  // Vertex A
  node((0, 0), $a$, name: <a>),
  node((inn-dist*calc.cos(60deg), -inn-dist*calc.sin(60deg)), $b$, name: <b>),
  node((-inn-dist*calc.cos(60deg), -inn-dist*calc.sin(60deg)), $c$, name: <c>),
  node([], enclose: (<a>, <b>, <c>), stroke: orange, shape: triangle,),
)

produces the following plot:

I was trying to use the enclose option to easily create a triangular contour around the nodes a, b, and c, but for some reason, the contour is way too wide and high, despite wrapping fairly tightly the bottom of the bottom nodes.

I have tried adjusting things like the inset and outset of that node, but it doesn’t do anything. Does anyone have a solution and/or explanation for why the enclose node is wrapping so loosely?

[Jollywatt]

This is because all node have rectangular bounding boxes, according to the model of nodes in fletcher’s layout algorithm. Most node shapes do, however, have a fit parameter which you can use to control how tightly the shape fits in/around the node’s rectangular bounds.

For example, changing the last line to

node([], enclose: (<a>, <b>, <c>), stroke: orange, shape: triangle.with(fit: 0.2)),

results in:

See the “Node shapes” section of the manual or search for the “fit” keyword for details.