Hi Doug, At 2025-05-02T19:47:45-0400, Douglas McIlroy wrote: > > To illustrate, in the following "A" means an output line requiring > > adjustment; "F" a line that is "full" and does not; and "L" and "R" > > indicate distribution of adjustment spaces from the left and right, > > respectively. > > > groff 1.22.4 groff 1.23.0 > > ------------ ------------ > > A L A L > > A R A R > > F L F R > > A R A L > > Possibly ambiguous wording.
Very likely. Unfortunately commit messages are unrevisable, so when trying to explain myself in them, I get stuck with my first draft forever--and few writers benefit from aggressive editorial attention more than I. > Does a line that is exactly full before adjustment "require > adjustment?" My guess is yes. As I conceptualize it, no. The line is already in perfect adjustment. Relatedly, the `distribute_space()` function in GNU troff returns early if (1) there amount of space required to bring the output line up to the configured line length is zero; (2) no adjustable spaces exist on the output line; or (3) the output line is already overset. https://git.savannah.gnu.org/cgit/groff.git/tree/src/roff/troff/env.cpp?id=d96a9c58bbe296b065fa250e3ea1e1a410cdde81#n2185 (If we implemented a "squeezing" algorithm, and condition (2) did not hold, we could instead proceed with it.) > On the other hand, a partially full line at the end of an adjusted > paragraph does not require adjustment. Agreed. > If my yes guess is wrong, I would call the situation a violation of > Kernighan's rul, "Do nothing gracefully." I don't _think_ we're violating it, and I think my 2023 change to the formatter hews to the principle better. If a line is adequately full (because it either matches the line length or ends a paragraph), then its presence does not perturb "adjustment parity". I guess another way of saying this is that, as I conceive it, a line that is "adequately full" contributes to the page's uniformity of grayness by definition. The foregoing is my understanding of the relevant typographical principles as I learned them from GNU troff's source code and behavior, not a vociferous prescription. I brought relatively few "priors" in the Bayesian sense to his domain. Incidentally, I recently changed GNU troff to tell you by how much adjusted lines are over- or underset, when that eventuates.[1] I dare say that these diagnostics are more readily apprehended by the non-expert than TeX's (notorious?) "overfull hbox" messages. Yeah, that's right--I'm droppin' my Donald Knuth diss track. Regards, Branden [1] Test script output: $ ../src/roff/groff/tests/warn-on-overset-adjusted-line.sh verifying that overset filled line warns in nroff mode <beginning of page> ### troff:<standard input>:4: warning [page 1, line 2]: cannot adjust line; overset by 1n ABCD verifying that overset filled line warns in troff mode <beginning of page> ### troff:<standard input>:4: warning [page 1, 0.2i]: cannot adjust line; overset by 0.1775i ABCD $ ../src/roff/groff/tests/warn-on-overset-unadjusted-line.sh verifying that overset left-aligned line warns in nroff mode <beginning of page> ### troff:<standard input>:5: warning [page 1, line 2]: cannot break line; overset by 1n ABCD verifying that overset left-aligned line warns in troff mode <beginning of page> ### troff:<standard input>:5: warning [page 1, 0.2i]: cannot break line; overset by 0.1775i ABCD verifying that overset right-aligned line warns in nroff mode <beginning of page> ### troff:<standard input>:5: warning [page 1, line 2]: cannot break line; overset by 1n ABCD verifying that overset right-aligned line warns in troff mode <beginning of page> ### troff:<standard input>:5: warning [page 1, 0.2i]: cannot break line; overset by 0.1775i ABCD verifying that overset center-aligned line warns in nroff mode <beginning of page> ### troff:<standard input>:5: warning [page 1, line 2]: cannot break line; overset by 1n ABCD verifying that overset center-aligned line warns in troff mode <beginning of page> ### troff:<standard input>:5: warning [page 1, 0.2i]: cannot break line; overset by 0.1775i ABCD $ ../src/roff/groff/tests/warn-on-underset-adjusted-line.sh verifying that underset filled line warns in nroff mode <beginning of page> ### troff:<standard input>:5: warning [page 1, line 2]: cannot adjust line; underset by 1n A B verifying that underset filled line warns in troff mode <beginning of page> ### troff:<standard input>:5: warning [page 1, 0.2i]: cannot adjust line; underset by 0.0733333i A B
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