Fletcher: how to apply inset for certain nested objects only?

[aurel]

Hi, I am trying to create a fletcher diagram. It includes a box which encloses two other boxes. These boxes should be inset from the enclosing box at 1em. Now I want to also set some text at the top-left corner of the enclosing box. This text should not be inset.
Is there a solution to this?

This is what I have come up with:

#import "@preview/fletcher:0.5.8" as fletcher: diagram, node, edge
#diagram(
  node-stroke: 0.5pt,
  spacing: 1em,
  node(enclose: (<2>, <3>), inset: 1em, align(top+left,
  text(size:8pt)[A short description]), name: <1>),
  node((0,4), [Some box], name: <2>),
  edge("-|>"),
  node((0,5), [Some other box], name: <3>),
)

#let node = node.with(shape: rect, corner-radius: 4pt)
#diagram(
  node-stroke: 0.5pt,
  spacing: 1em,
  node(enclose: (<2>, <3>), inset: 1em, name: <1>),
  node((rel: (0, 0), to: <1.north-west>), align(left, text(size:8pt)[A
  description]), inset: 0.1em),
  node((0,4), [Some box], name: <2>),
  edge("-|>"),
  node((0,5), [Some other box], name: <3>),
)

But you can see, both are not ideal. Basically I want the description to just be placed at the top-left of the enclosing box, with no inset.

[janekfleper]

You could add an additional node that encloses the node <1> with the inset set to 0. I have no idea whether this is actually the best approach though, I have not spent a lot of time working with fletcher so far.

#import "@preview/fletcher:0.5.8" as fletcher: diagram, node, edge
#let node = node.with(shape: rect, corner-radius: 4pt)

#diagram(
  node-stroke: 0.5pt,
  spacing: 1em,
  node(
    enclose: (<1>,),
    inset: 0em,
    stroke: none,
    align(
      top + left,
      text(size: 8pt)[A short description],
    ),
  ),
  node(
    enclose: (<2>, <3>),
    inset: 1em,
    name: <1>
  ),
  node((0,4), [Some box], name: <2>),
  edge("-|>"),
  node((0,5), [Some other box], name: <3>),
)

A second option would be to use place() instead of align() with the negative inset of the enclosing node applied to dx and dy.

#import "@preview/fletcher:0.5.8" as fletcher: diagram, node, edge
#let node = node.with(shape: rect, corner-radius: 4pt)

#diagram(
  node-stroke: 0.5pt,
  spacing: 1em,
  node(
    enclose: (<2>, <3>),
    inset: 1em,
    place(
      dx: -1em,
      dy: -1em,
      top + left,
      text(size: 8pt)[A short description],
    ),
    name: <1>
  ),
  node((0,4), [Some box], name: <2>),
  edge("-|>"),
  node((0,5), [Some other box], name: <3>),
)

[aurel]

First of: Thank you very much for your help!

Do you know if there is a way to specify the anchor point of the node I am placing? Then, one could simply use my second approach and specify its anchor to be top-left as well. This would place the box perfectly on the enclosing box.

[aurel]

I used the second proposed solution, as it let me adjust some smaller spacing to the stroke of the enclosing node.
Thank you very much for your help!

[Jollywatt]

Another way is to add negative padding around the text label of the enclosing node.

#import "@preview/fletcher:0.5.8" as fletcher: diagram, node, edge

#diagram(
  node-stroke: 0.5pt,
  spacing: 1em,
  let label = pad(-1em, text(size:8pt)[A short description]),
  node(enclose: (<2>, <3>), inset: 1.3em, align(top+left, label), name: <1>),
  node((0,4), [Some box], name: <2>),
  edge("-|>"),
  node((0,5), [Some other box], name: <3>),
)