Re: [Groff] PIC: access global labels from within a [] block

[Tadziu Hoffmann]

(Posted to the list because of possible general interest.)

> > A bracketed block can be treated as a single unit and
> > aligned like any primitive object, but I don't think it
> > is possible to align the entire block by specifying an
> > "absolute" position for an internal sub-component of
> > the block.

> One can position a sub-component inside a block using
> "with .sub-component.s at GLOBAL.s" with alignment
> consequences for the entire block.

Indeed, this is possible.  My bad.

What does not work is positioning subcomponents individually
relative to outside objects:

  A: box "A"
  B: [
    C: box "C"
    arrow
    D: box "D" with .n at A.s + (0,-.1)
  ]

(but you can position D relative to C).

What does work is positioning the entire block:

  A: box "A"
  B: [
    C: box "C"
    arrow
    D: box "D"
  ] with .D.n at A.s + (0,-.1)

i.e., the block itself has a single alignment specification,
but this can refer to a sub-component.


> The problem arises, however, when one tries to position two
> sub-components of the block independently with respect to
> outer objects.

Yes, like in the first example above.

> Suppose I have  two global boxes (GLOBAL1 and GLOBAL2) and
> then a block with two boxes (A and B):
>
> .PS
> GLOBAL1: box
> GLOBAL2: box
> .... some crooked movement here ...
> BLOCK: [
>   A: box
>   B: box
> ]
> .PE
>
> I want to position A under GLOBAL1 and B under GLOBAL2 respectively,
> i.e. to make BLOCK.A.c.y = GLOBAL1.c.y and BLOCK.B.c.y = GLOBAL2.c.y.

Are the global boxes constrained?

If not, then a possible solution to your layout problem might be
to align GLOBAL1 and GLOBAL2 relative to BLOCK.A resp. BLOCK.B:

  BLOCK: [
    A: box "A"
    move
    B: box "B"
  ]
  LOCAL: box width BLOCK.wid+.5 height BLOCK.ht+.5 with .c at BLOCK.c
  "Local" at LOCAL.nw + (.05,-.02) below ljust
  GLOBAL1: box "G1" with .s at BLOCK.A.n + (0,.75)
  GLOBAL2: box "G2" with .s at BLOCK.B.n + (0,.75)