Re: Proposed: make \X read its argument in copy mode

[G. Branden Robinson]

[self-follow-up with correction]

At 2024-01-19T18:56:37-0600, G. Branden Robinson wrote:
> This might be more accurately stated as:
> 
> 2) \X behaves like .device used to (in groff 1.23.0 and earlier).

[correction follows]
And I repeat: this is _NOT_ a _hard_ prerequisite to expressing Unicode
sequences in the output, but it seems useful so that authors of output
drivers (and supporting macro files for them) can keep their sanity.

[elaboration]

What I mean is that we can pass Unicode between "pdf.tmac" and the
output driver _today_.  Consider the following notional macro.

.de pdfmark2
. nop \!x X ps:exec [\\$* pdfmark2
..

(The open bracket has something to do with PostScript syntax, I think.)

...and it getting called by some other macro encoding the argument...

.de pdflink
.  ds pdf*input \\$*\"
.  encode pdf*input \" performs magic transformation, like "stringhex"
.  pdfmark2 \\*[pdf*input]
..

...and I have document using these.

.H 1 "This is my heading"
.pdflink "HI DERI 😈"

This ultimately would show up in the output as something like this.

x X ps: exec [4849204445524920F09F9888 pdfmark2

Something pretty close to that works on the deri-gropdf-ng branch today,
as I understand it.

But my _suggestion_ would be that we support something more like this.

x X ps: exec [HI DERI \[u00F0]\[u009F]\[u0098]\[u0088] pdfmark2

or this...

x X ps: exec [HI DERI \[uDE08]\[uD83D] pdfmark2

...or even this...

x X ps: exec [HI DERI \[u1F608] pdfmark2

These are groffish ways of expressing UTF-8, UTF-16LE, and UTF-32,
respectively.  The reuse of groff Unicode code point escape sequence
syntax is, I would hope, more helpful than confusing.

My concerns are that (1) people don't have to use two different escaping
conventions _within the formatter_ to get byte sequences to the output
driver, and (2) that driver-supporting macro file writers don't have to
handle a bunch of special cases in device control commands.

Those factors are what drive my proposal.

Regards,
Branden

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