Follow-up Comment #2, bug#64231 (group groff): Bug #64232 turned out to be invalid; what I wanted was already the case.
This matter was explored more deeply by Tadziu and me in a thread on the _groff_ list. https://lists.gnu.org/archive/html/groff/2024-01/msg00019.html https://lists.gnu.org/archive/html/groff/2024-01/msg00032.html https://lists.gnu.org/archive/html/groff/2024-01/msg00040.html https://lists.gnu.org/archive/html/groff/2024-01/msg00041.html https://lists.gnu.org/archive/html/groff/2024-01/msg00048.html https://lists.gnu.org/archive/html/groff/2024-01/msg00050.html The most pertinent part for this ticket is likely the following. ...[N]othing in eqn documents its sensitivity to the font mounting order when determining the typefaces to be used. In fact that sensitivity overrides explicit configuration! Source: $ cat ATTIC/to-slant-or-not-to-slant.roff .\" "letter" means "slanted" in GNU eqn .\" This is actually redundant with the default configuration. .EQ chartype "letter" \[*a]\[*b]\[*g]\[*d]\[*e]\[*z] chartype "letter" \[*y]\[*h]\[*i]\[*k]\[*l]\[*m] chartype "letter" \[*n]\[*c]\[*o]\[*p]\[*r]\[*s] chartype "letter" \[*t]\[*u]\[*f]\[*x]\[*q]\[*w] .EN .fp 5 S .fp 6 SS \(*A\(*a \(-> upright lowercase alpha .br .EQ sin ( 2 theta ) ~ = ~ 2 ~ sin theta cos theta .EN .sp .fp 5 SS .fp 6 S \(*A\(*a \(-> slanted lowercase alpha .br .EQ sin ( 2 theta ) ~ = ~ 2 ~ sin theta cos theta .EN Rendering: [see attached image] > Example: > > .fp 5 S > .fp 6 SS > \(*A\(*a --> upright lowercase alpha. > .fp 5 SS > .fp 6 S > \(*A\(*a --> slanted lowercase alpha. This is fine, but it's raw *roff, not eqn input. I am concerned with eqn output, and nothing I propose would break your exhibit above. At 2024-01-10T02:10:12+0100, Tadziu Hoffmann wrote: > > I never knew this. Where is the reference please? > > I would like to mention this in my new EQN manual. > > The Troff User's Manual (section 2, "Font and Character Size > Control") says: > > The troff character set is defined by a description file > specific to each output device. There are normally several > regular fonts and one or more special fonts. > > Troff begins execution by reading information for a set of > defaults fonts, said to be mounted; conventionally, the first > four are Times Roman (R), Times Italic (I), Times Bold (B), > and Times Bold Italic (BI), and the last is a Special font (S) > containing miscellaneous characters. The set of fonts and > positions is determined by the device description file. > > It is not necessary to change to the Special font; > characters on that font are automatically handled as if > they were physically part of the current font. The Special > font may actually be several fonts; the name S is reserved > and is generally used for one of these. All special fonts > must be mounted after regular fonts. > > However, it does not explicitly say that the special fonts > are searched in mount-position order. (I think it is a > reasonable assumption, but I may be biased.) > > The groff Info file (section 5.17.4, "Using Symbols") is more > specific: > > Here are the exact rules how 'gtroff' searches a given symbol: > > [... current font and explicit declarations using > .char and .fspecial ...] > > * As a last resort, consult all fonts loaded up to now for > special fonts and check them, starting with the lowest > font number. [...] > > Since both S and SS contain lowercase Greek characters, placing > SS before S will result in gtroff picking the slanted alpha for > \(*a, whereas placing S before SS with pick the upright alpha. > (Unless of course the current font also contains a \(*a character, > in which case this will be used, or any other font declared > as special and containing \(*a is mounted before S and SS.) I don't propose to change any of this. It seems to work well and can be apprehended by users. ... [3] This in turn means that the definitions of the eqn Greek-letter-name macros will _have_ to come out of the lexer and be put in eqn-device-specific startup logic--in eqnrc, say--so that the code can be appropriately conditionalized. Only the "ps" device has (though, soon, "pdf" will have) a font called "SS" by default. So I envision something like this in eqnrc: ifdef utf8 ! define Alpha \*(A ! ifdef utf8 ! define ALPHA \*(A ! ifdef utf8 ! define alpha \fI\*(a\fP ! ifdef ps|pdf ! define Alpha \*(A ! ifdef ps|pdf ! define ALPHA \*(A ! ifdef ps|pdf ! define alpha \f(SS\*(a\fP ! ...and so on for the other 23 Greek letters. _______________________________________________________ Reply to this item at: <https://savannah.gnu.org/bugs/?64231> _______________________________________________ Message sent via Savannah https://savannah.gnu.org/
