[gropdf]: Clarify reduced support scenario.

* font/devpdf/tests/basic-fonts-present.sh: Revise test.  Improve
  explanation of why we're looking for the gs(1) command in a font
  availability test.  Prefix diagnostic output with name of test script.
  Perform a search for the 'ps' device font descriptions that will work
  in more build scenarios (i.e., don't assume an out-of-tree build
  taking place in an immediate subdirectory of the source).  Distinguish
  failure to find the font descriptions from a failure to locate the
  'gs' command, skipping the test in both scenarios.  Reduce noise in
  output.

* m4/groff.m4 (GROFF_CHECK_GROPDF_PROGRAMS): Revise warning issued when
  awk and Ghostscript are unavailable; gropdf will not be completely
  inoperative.  Characterize its reduced function.

Thanks to Deri James in <https://lists.gnu.org/archive/html/\
groff-commit/2023-02/msg00089.html> for prompting me to take a another
look at this.

1 files changed, 36 insertions, 7 deletions

diff --git a/font/devpdf/tests/basic-fonts-present.sh b/font/devpdf/tests/basic-fonts-present.sh
index b373dfc0f..f54534697 100755
--- a/font/devpdf/tests/basic-fonts-present.sh
+++ b/font/devpdf/tests/basic-fonts-present.sh
@@ -1,6 +1,6 @@
 #!/bin/sh
 #
-# Copyright (C) 2022 Free Software Foundation, Inc.
+# Copyright (C) 2022-2023 Free Software Foundation, Inc.
 #
 # This file is part of groff.
 #
@@ -23,15 +23,45 @@
 #
 # We need all of them except SS and ZDR.
 
-# Our configure script warns that gropdf will not be functional if gs
-# (Ghostscript) is not available.
+# Our configure script warns that gropdf will not be fully functional if
+# gs (Ghostscript) is not available.  Namely, we will have only
+# descriptions for the PostScript Level 1 base 14 fonts, not the Level 2
+# base 35 fonts.  We're using the presence of the command as a proxy for
+# the availabilty of the fonts because locating the latter is
+# unreliable (package names, directory locations, and file names all
+# vary), but if the command is present, the fonts usually are too.
 if ! command -v gs
 then
-    echo "gs command not available; skipping test" >&2
+    echo "$0: gs command not available; skipping test" >&2
+    exit 77 # skip
+fi
+
+# Locate directory containing the font descriptions for the PostScript
+# device.
+for srcroot in . .. ../..
+do
+    # Look for a source file characteristic of the groff source tree.
+    if ! [ -f "$srcroot"/ChangeLog.115 ]
+    then
+        continue
+    fi
+
+    d=$srcroot/font/devps
+    if [ -d "$d" ]
+    then
+        devps_fontsrcdir=$d
+        break
+    fi
+done
+
+# If we can't find it, we can't test.
+if [ -z "$devps_fontsrcdir" ]
+then
+    echo "$0: cannot locate font descriptions for 'ps' device;" \
+        "skipping test" >&2
     exit 77 # skip
 fi
 
-devps_fontsrcdir="${abs_top_srcdir:-..}"/font/devps
 devpdf_fontbuilddir="${abs_top_builddir:-.}"/font/devpdf
 
 psfonts=$(cd "$devps_fontsrcdir" && ls [A-Z]* \
@@ -42,9 +72,8 @@ fail=
 for f in $psfonts
 do
     printf "checking for font description %s...\n" "$f" >&2
-    if ! test -f "$devpdf_fontbuilddir"/"$f"
+    if ! [ -f "$devpdf_fontbuilddir"/"$f" ]
     then
-        echo test -f "$devpdf_fontbuilddir"/"$f"
         echo FAILED >&2
         fail=yes
     fi