[bug #55070] [wishlist] Next-generation hyphenation control

[G. Branden Robinson]

URL:
<https://savannah.gnu.org/bugs/?55070>

Summary: [wishlist] Next-generation hyphenation control
Project: GNU troff
Submitted by: gbranden
Submitted on: Wed 21 Nov 2018 08:00:51 PM UTC
Category: Core
Severity: 1 - Wish
Item Group: Wishlist
Status: None
Privacy: Public
Assigned to: None
Open/Closed: Open
Discussion Lock: Any
Planned Release: None

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Details:

See comments on <https://savannah.gnu.org/bugs/index.php?55066> for
background. Someone may be willing to add comments linking to past mailing
list discussions as well.

In summary:

Three orthogonal ideas are intermixed in the semantics of the roff .hy
request. Quoting CSTR #54:

"Automatic hyphenation is turned on for N ≥ 1, or off for N = 0. If N = 2,
last lines (ones that will cause a trap) are not hyphenated. For N = 4 and 8,
the last and first two characters respectively of a word are not split off.
These values are additive; i.e., N = 14 will invoke all three restrictions."

However this design does not scale to languages which permit hyphenation after
the first or before the last letter of a word.

There should therefore be 3 separate controls:

* minimum left-length before hyphenation occurs;
* minimum right-length before hyphenation occurs;
* whether hyphenation of the last line of a page or column is permitted.

And in fact, the last item could also be split in two; column-hyphenated
orphans could be permitted when page ones are not (or, _very_ perversely, vice
versa).

The orthogonality of these concepts is not theoretically perfect, as in the
case where left-minimum + right-minimum > word-length, there is some
ambiguity, but this is only in theory. In practice the result is that such a
word is not hyphenated.




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[Bertrand Garrigues]

Update of bug #55070 (project groff):

Severity: 1 - Wish => 3 - Normal

[Dave]

Follow-up Comment #1, bug #55070 (project groff):

Bug #53837 is another request for more advanced control over hyphenation. The
issues are not strongly related, but both involve an overhaul in fundamental
ways hyphenation is controlled, so perhaps should be considered in tandem.

[Dave]

Follow-up Comment #2, bug #55070 (project groff):

Actually all these bug reports are feature requests involving the low-level
hyphenation mechanism.

* bug #55070 (this bug)
* bug #53837 (mentioned in comment #1)
* bug #57556
* bug #42870

For completeness (rounding up all the bugs dealing with hyphenation), these
bugs document changes needed within the existing hyphenation framework,
independent of any of the upgrades above:

* bug #57616
* bug #57601
* bug #57594
* bug #57561
* bug #53413

And, for good measure, one bug dealing not with hyphenation per se, but with
line breaking around hyphens in the document text:

* bug #57448

Besides creating a new category, which I don't think is appropriate here, I
don't know if this bug tracker offers a convenient way to group all these bugs
together (or if anyone even thinks that's important). Few if any are
dependent on the others. Maybe open a master "hyphenation issues" bug that
has all these as dependencies?