[groff] 24/31: [pic]: Recognize `.PY` as synonym of `.PF`.

[G. Branden Robinson]

gbranden pushed a commit to branch master
in repository groff.

commit 1ac8764fa7f3b91e7d2a84261edbdc84c1ae4158
Author: G. Branden Robinson <g.branden.robinson@gmail.com>
AuthorDate: Sun Aug 14 23:52:40 2022 -0500

    [pic]: Recognize `.PY` as synonym of `.PF`.
    
    * src/preproc/pic/main.cpp:
    * src/preproc/pic/pic.h: Add new Boolean variable,
      `want_alternate_flyback` to record `.PY` usage.
    
    * src/preproc/pic/main.cpp (top_input::get, top_input::peek): Recognize
      it.  Update diagnostic messages to mention it.
    
      (main): Define `PY` troff macro as empty if not defined.
    
    * src/preproc/pic/troff.cpp (troff_output::finish_picture): Don't
      advance the vertical position if `want_alternate_flyback`.  Write out
      the `PY` macro call if it was on the input.
    
    * src/preproc/pic/pic.1.man: Document it.
    
    * tmac/pic.tmac (PY): Define the same as `PF`.
    
    * NEWS: Add item.
    
    Fixes <https://savannah.gnu.org/bugs/?62901>.
    
    Also drop old-style Emacs file-local variable settings.
---
 ChangeLog                 | 24 ++++++++++++++++++++++++
 NEWS                      | 10 ++++++++++
 src/preproc/pic/main.cpp  | 15 ++++++++++-----
 src/preproc/pic/pic.1.man | 47 ++++++++++++++++++++++++++++++++++-------------
 src/preproc/pic/pic.h     |  2 +-
 src/preproc/pic/troff.cpp |  9 +++++++--
 tmac/pic.tmac             |  5 +++--
 7 files changed, 89 insertions(+), 23 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 1ae835017..4bddb824d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,27 @@
+2022-08-14  G. Branden Robinson <g.branden.robinson@gmail.com>
+
+       [pic]: Recognize `.PY` as synonym of `.PF`.
+
+       * src/preproc/pic/main.cpp:
+       * src/preproc/pic/pic.h: Add new Boolean variable,
+       `want_alternate_flyback` to record `.PY` usage.
+
+       * src/preproc/pic/main.cpp (top_input::get, top_input::peek):
+       Recognize it.  Update diagnostic messages to mention it.
+       (main): Define `PY` troff macro as empty if not defined.
+
+       * src/preproc/pic/troff.cpp (troff_output::finish_picture):
+       Don't advance the vertical position if `want_alternate_flyback`.
+       Write out the `PY` macro call if it was on the input.
+
+       * src/preproc/pic/pic.1.man: Document it.
+
+       * tmac/pic.tmac (PY): Define the same as `PF`.
+
+       * NEWS: Add item.
+
+       Fixes <https://savannah.gnu.org/bugs/?62901>.
+
 2022-08-14  G. Branden Robinson <g.branden.robinson@gmail.com>
 
        [pic]: Refactor `flyback_flag`.
diff --git a/NEWS b/NEWS
index ec8447044..1ddf66b6f 100644
--- a/NEWS
+++ b/NEWS
@@ -115,6 +115,16 @@ o The GNU extension
   to use 'o' and 'n' as left and right delimiters, respectively.  If
   yours does, consider swapping them, or select others.
 
+pic
+---
+
+o The token `.PY` is now recognized as a synonym of `.PF` to work around
+  a name space collision with the m (mm) macro package, which uses the
+  same name for a page footer management macro.  (This problem dates
+  back at least to Unix System V Release 2, 1983.)  You should continue
+  to use `.PF` to end pictures with flyback unless a similar problem
+  faces your document.
+
 Macro packages
 --------------
 
diff --git a/src/preproc/pic/main.cpp b/src/preproc/pic/main.cpp
index 233e4c177..114ca2158 100644
--- a/src/preproc/pic/main.cpp
+++ b/src/preproc/pic/main.cpp
@@ -25,6 +25,8 @@ output *out;
 char *graphname;               // the picture box name in TeX mode
 
 bool want_flyback = false;
+// groff pic supports '.PY' to work around mm package stepping on 'PF'.
+bool want_alternate_flyback = false;
 int zero_length_line_flag = 0;
 // Non-zero means we're using a groff driver.
 int driver_extension_flag = 1;
@@ -88,13 +90,14 @@ int top_input::get()
     c = getc(fp);
     if (c == 'P') {
       c = getc(fp);
-      if (c == 'F' || c == 'E') {
+      if (c == 'E' || c == 'F' || c == 'Y') {
        int d = getc(fp);
        if (d != EOF)
          ungetc(d, fp);
        if (d == EOF || d == ' ' || d == '\n' || compatible_flag) {
          eof = 1;
          want_flyback = (c == 'F');
+         want_alternate_flyback = (c == 'Y');
          return EOF;
        }
        push_back[0] = c;
@@ -133,7 +136,7 @@ int top_input::get()
   bol = 0;
   if (c == EOF) {
     eof = 1;
-    error("end of file before .PE or .PF");
+    error("end of file before .PE, .PF, or .PY");
     error_with_file_and_line(current_filename, start_lineno - 1,
                             ".PS was here");
   }
@@ -160,13 +163,14 @@ int top_input::peek()
     c = getc(fp);
     if (c == 'P') {
       c = getc(fp);
-      if (c == 'F' || c == 'E') {
+      if (c == 'E' || c == 'F' || c == 'Y') {
        int d = getc(fp);
        if (d != EOF)
          ungetc(d, fp);
        if (d == EOF || d == ' ' || d == '\n' || compatible_flag) {
          eof = 1;
          want_flyback = (c == 'F');
+         want_alternate_flyback = (c == 'Y');
          return EOF;
        }
        push_back[0] = c;
@@ -287,7 +291,7 @@ void do_picture(FILE *fp)
     parse_cleanup();
     lex_cleanup();
 
-    // skip the rest of the .PF/.PE line
+    // skip the rest of the .PE/.PF/.PY line
     while ((c = getc(fp)) != EOF && c != '\n')
       ;
     if (c == '\n')
@@ -622,7 +626,8 @@ int main(int argc, char **argv)
     out = make_troff_output();
     printf(".do if !dPS .ds PS\n"
           ".do if !dPE .ds PE\n"
-          ".do if !dPF .ds PF\n");
+          ".do if !dPF .ds PF\n"
+          ".do if !dPY .ds PY\n");
   }
 #ifdef FIG_SUPPORT
   if (whole_file_flag) {
diff --git a/src/preproc/pic/pic.1.man b/src/preproc/pic/pic.1.man
index 7c4a4eca5..6dc803e4b 100644
--- a/src/preproc/pic/pic.1.man
+++ b/src/preproc/pic/pic.1.man
@@ -101,10 +101,11 @@ It copies the contents of each
 to the standard output stream,
 except that lines between
 .B .PS
-and either
-.B .PE
+and any of
+.BR .PE ,
+.BR .PF ,
 or
-.B .PF
+.B .PY
 are interpreted as picture descriptions.
 .
 Ending a
@@ -114,6 +115,8 @@ picture with
 leaves the page position at the bottom of the picture;
 ending it with
 .B .PF
+or
+.B .PY
 leaves the position at the top.
 .
 Normally,
@@ -134,24 +137,40 @@ is
 the standard input stream is read.
 .
 .
-.LP
+.P
 It is the user's responsibility to provide appropriate definitions
 of the
 .BR PS ,
 .BR PE ,
-and
+and one or both of the
 .B PF
+and
+.B PY
 macros.
 .
-When the macro package being used does not supply such definitions
-(for example,
-old versions of \-ms),
-appropriate definitions can be
-obtained with
+When a macro package does not supply these,
+appropriate definitions can be obtained with
 .BR \-mpic ;
 these will center each picture.
 .
 .
+.P
+GNU
+.I pic \" GNU
+supports
+.B PY
+as a synonym of
+.B PF
+to work around a name space collision with the
+.I mm
+macro package,
+which uses the same name for a page footer management macro.
+.
+Use
+.B PF
+preferentially unless a similar problem faces your document.
+.
+.
 .\" ====================================================================
 .SH Options
 .\" ====================================================================
@@ -207,8 +226,9 @@ variable.
 Recognize
 .BR .PS ,
 .BR .PE ,
+.BR .PF ,
 and
-.B .PF
+.B .PY
 even when followed by a character other than space or newline.
 .
 .
@@ -1443,11 +1463,12 @@ package.
 .
 .TP
 .I @MACRODIR@/pic.tmac
-Example definitions of the
+offers simple definitions of the
 .BR PS ,
 .BR PE ,
+.BR PF ,
 and
-.B PF
+.B PY
 macros.
 .
 .
diff --git a/src/preproc/pic/pic.h b/src/preproc/pic/pic.h
index d052c1a89..8baca154e 100644
--- a/src/preproc/pic/pic.h
+++ b/src/preproc/pic/pic.h
@@ -1,4 +1,3 @@
-// -*- C++ -*-
 /* Copyright (C) 1989-2020 Free Software Foundation, Inc.
      Written by James Clark (jjc@jclark.com)
 
@@ -112,6 +111,7 @@ void lex_warning(const char *message,
 void lex_cleanup();
 
 extern bool want_flyback;
+extern bool want_alternate_flyback;
 extern int command_char;
 // zero_length_line_flag is non-zero if zero-length lines are drawn 
 // as dots by the output device
diff --git a/src/preproc/pic/troff.cpp b/src/preproc/pic/troff.cpp
index ad8998446..3dc87a721 100644
--- a/src/preproc/pic/troff.cpp
+++ b/src/preproc/pic/troff.cpp
@@ -298,14 +298,19 @@ void troff_output::finish_picture()
   line_thickness(BAD_THICKNESS);
   last_fill = -1.0;            // force it to be reset for each picture
   reset_color();
-  if (!want_flyback)
+  if (!(want_flyback || want_alternate_flyback))
     printf(".sp %.3fi+1\n", height);
   printf(".if \\n(" FILL_REG " .fi\n");
   printf(".br\n");
   printf(".nr " EQN_NO_EXTRA_SPACE_REG " 0\n");
   // this is a little gross
   set_location(current_filename, current_lineno);
-  fputs(want_flyback ? ".PF\n" : ".PE\n", stdout);
+  if (want_flyback)
+    fputs(".PF\n", stdout);
+  else if (want_alternate_flyback)
+    fputs(".PY\n", stdout);
+  else
+    fputs(".PE\n", stdout);
 }
 
 void troff_output::command(const char *s,
diff --git a/tmac/pic.tmac b/tmac/pic.tmac
index 6bbe874a6..d4aaaa479 100644
--- a/tmac/pic.tmac
+++ b/tmac/pic.tmac
@@ -1,5 +1,3 @@
-.\" -*- nroff -*-
-.\"
 .\" pic.tmac
 .\"
 .de PS
@@ -15,6 +13,9 @@
 .PF
 .sp .3v+.5m
 ..
+.de PY
+.in
+..
 .
 .\" Local Variables:
 .\" mode: nroff