[TUHS] Re: Paragraphs formatted differently depending on previous ones

[looping the groff list back in; Doug emailed TUHS instead] At 2025-05-03T08:14:18-0400, Douglas McIlroy wrote: Yes. `distribute_space()` is in "env.cpp" (environment handling) and operates on the output line. `spread_space()` is in "node.cpp" and is what alters the width of `word_space_node` (and derived `unbreakable_space_node`) objects on the line. Whereas in troff mode, often every adjustable space on an underset line experiences adjustment, in nroff mode the converse is frequently true, as shown below. Some of this stuff will be more visible for debugging purposes with the new `pline` request and improved `pm` request in the forthcoming groff 1.24.0 release. Here's an altered version of the adjustment demonstrator I cooked up for Alex. It uses a shorter line length and fewer repetitions of "alex", but still illustrates alternating adjustment "parity", as I term it. $ { echo .ll 15n; echo .di dd; for n in $(seq 7); do echo alex; done; \ printf '.pl \\n(nlu\n'; echo .di; echo .pm dd; echo .dd; } \ | nroff 2>/dev/null | cat -s alex alex alex alex alex alex alex If we discard normal output with the `-z` option, reënable output to standard error, and send that to jq(1) for formatting, we get more information, which I'll relegate to a footnote because it's lengthy.[1] It also serves to illustrate how we can dump diversions, and the intriguing properties thereof in GNU troff. $ { echo .ll 15n; echo .di dd; for n in $(seq 7); do echo alex; done; \ printf '.pl \\n(nlu\n'; echo .di; echo .pm dd; } | nroff -z 2>&1 | jq The first computer I ever touched, and programmed, had 16 KB of RAM. Necessity is a mother in more than one sense. ;-) I'm doing what I can with the GNU troff code base to make it more intelligible. Among the windmills I'm tilting at are improved type annotations (like using `bool` for Booleans instead of integers for Yet Another Purpose), explicitly annotated null pointers, and above all, more meaningful variable and function names. Kernighan and Plauger, then Pike, beat this drum repeatedly in their books on programming style, but we're still not rid of hackers who think naming a variable `bflag` is a good idea. Thank you! The reformed handling of device extension requests/escapes so that they could encode Unicode characters, and their conversion into nodes, was almost more murk than I could stand. I think it might have helped to have some of the new introspection features 12-18 months ago, but we have them now. There's always more to learn, and to document. For those who hadn't noticed, I'll put the relevant part of the "NEWS" file in another footnote.[2] I'm on the verge of adding another, `pftr`, to dump the dictionary of font translations (remappings), because mdoc is proving to be a headache this week with Savannah #66126. Regards, Branden [1] Observe how some of the `word_space_node`s have a width of `24`, and others a width of `48`. The latter are the "adjusted" spaces. $ { echo .ll 15n; echo .di dd; for n in $(seq 7); do echo alex; done; printf '.pl \\n(nlu\n'; echo .di; echo .pm dd; } | nroff -z 2>&1 | jq { "name": "dd", "file name": "<standard input>", "starting line number": 2, "length": 35, "contents": "\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\n\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\n", "node list": [ { "type": "line_start_node", "diversion level": 0, "is_special_node": false }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "a" }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "l" }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "e" }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "x" }, { "type": "word_space_node", "diversion level": 0, "is_special_node": false, "hunits": 48, "undiscardable": true, "is hyphenless breakpoint": false, "terminal_color": "default", "width_list": [ { "width": 24, "sentence_width": 24 } ], "unformat": false }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "a" }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "l" }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "e" }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "x" }, { "type": "word_space_node", "diversion level": 0, "is_special_node": false, "hunits": 24, "undiscardable": true, "is hyphenless breakpoint": false, "terminal_color": "default", "width_list": [ { "width": 24, "sentence_width": 24 } ], "unformat": false }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "a" }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "l" }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "e" }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "x" }, { "type": "vertical_size_node", "diversion level": 0, "is_special_node": false, "vunits": -40 }, { "type": "vertical_size_node", "diversion level": 0, "is_special_node": false, "vunits": 0 }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "a" }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "l" }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "e" }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "x" }, { "type": "word_space_node", "diversion level": 0, "is_special_node": false, "hunits": 24, "undiscardable": true, "is hyphenless breakpoint": false, "terminal_color": "default", "width_list": [ { "width": 24, "sentence_width": 24 } ], "unformat": false }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "a" }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "l" }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "e" }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "x" }, { "type": "word_space_node", "diversion level": 0, "is_special_node": false, "hunits": 48, "undiscardable": true, "is hyphenless breakpoint": false, "terminal_color": "default", "width_list": [ { "width": 24, "sentence_width": 24 } ], "unformat": false }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "a" }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "l" }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "e" }, { "type": "glyph_node", "diversion level": 0, "is_special_node": false, "character": "x" }, { "type": "vertical_size_node", "diversion level": 0, "is_special_node": false, "vunits": -40 }, { "type": "vertical_size_node", "diversion level": 0, "is_special_node": false, "vunits": 0 } ] } [2] NEWS: ---snip--- * A new request, `pcolor`, reports to the standard error stream details of each color name specified as an argument, including its color space identifier and channel value assignments. Without arguments, all defined colors are listed. (A device's default stroke and/or fill colors, "default", are not listed since they are immutable and their details unknown to the formatter.) * A new request, `pchar`, reports to the standard error stream data about any ordinary, special, or indexed character arguments. * A new request, `pcomposite`, reports to the standard error stream the list of defined composite character mappings. * A new request, `phw`, reports to the standard error stream the list of hyphenation exceptions associated with the current hyphenation language. * A new request, `pline`, reports to the standard error stream the list of output nodes (an internal data structure) corresponding to the pending output line. The list is empty if no such nodes exist. * The `pm` request now interprets any arguments as a sequence of macro, string, or diversion names, and reports their contents. * The `pnr` request now additionally reports the autoincrementation amount and interpolation format of each register (if it is not string-valued). * The `pnr` request now accepts arguments. It treats each as identifying a register and reports its properties to the standard error stream. * A new request, `pstream`, reports to the standard error stream the name of each stream opened with the `open` or `opena` requests, the name of the file backing it, and its mode (writing or appending). ---end snip---