[grn, groff, troff]: Improve fatal diagnostics.

[grn, groff, troff]: Communicate better when device DESC file can't be
loaded.

* src/libs/libgroff/font.cpp (font::load_desc): Stop writing diagnostic
  to standard error.

* src/preproc/grn/main.cpp (getres):
* src/roff/troff/troff.cpp (main): Replace "sorry, I can't continue"
  fatal diagnostic with a more informative message.  Instead say
  which device's DESC file the program was trying to open, which might
  reveal a user's logic error or typo.

* src/roff/groff/groff.cpp (main): Replace "invalid device" text of
  fatal diagnostic similarly.  I think it is more helpful to indicate
  the operation that failed rather than saying the device was invalid,
  particularly since there are other ways for a device to be invalid
  even if a DESC file is found and loaded.

4 files changed, 9 insertions, 7 deletions

diff --git a/src/libs/libgroff/font.cpp b/src/libs/libgroff/font.cpp
index 861b04cbc..0c49ebb19 100644
--- a/src/libs/libgroff/font.cpp
+++ b/src/libs/libgroff/font.cpp
@@ -1035,10 +1035,8 @@ bool font::load_desc()
   int nfonts = 0;
   FILE *fp;
   char *path;
-  if ((fp = open_file("DESC", &path)) == 0) {
-    error("can't find 'DESC' file");
+  if ((fp = open_file("DESC", &path)) == 0)
     return false;
-  }
   text_file t(fp, path);
   t.skip_comments = 1;
   res = 0;
diff --git a/src/preproc/grn/main.cpp b/src/preproc/grn/main.cpp
index 3a2e332a9..c4a57a49f 100644
--- a/src/preproc/grn/main.cpp
+++ b/src/preproc/grn/main.cpp
@@ -429,7 +429,8 @@ getres()
   int linepiece;
 
   if (!font::load_desc())
-    fatal("sorry, I can't continue");
+    fatal("cannot load 'DESC' description file for device '%1'",
+	  device);
 
   res = font::res;
 
diff --git a/src/roff/groff/groff.cpp b/src/roff/groff/groff.cpp
index f83ab27c1..39c21e902 100644
--- a/src/roff/groff/groff.cpp
+++ b/src/roff/groff/groff.cpp
@@ -345,9 +345,11 @@ int main(int argc, char **argv)
   }
   font::set_unknown_desc_command_handler(handle_unknown_desc_command);
   if (!font::load_desc())
-    fatal("invalid device '%1'", device);
+    fatal("cannot load 'DESC' description file for device '%1'",
+	  device);
   if (!postdriver)
-    fatal("no 'postpro' command in DESC file for device '%1'", device);
+    fatal("no 'postpro' directive in 'DESC' file for device '%1'",
+          device);
   if (predriver && !zflag) {
     commands[TROFF_INDEX].insert_arg(commands[TROFF_INDEX].get_name());
     commands[TROFF_INDEX].set_name(predriver);
diff --git a/src/roff/troff/input.cpp b/src/roff/troff/input.cpp
index abe9bf013..6019dfea2 100644
--- a/src/roff/troff/input.cpp
+++ b/src/roff/troff/input.cpp
@@ -8127,7 +8127,8 @@ int main(int argc, char **argv)
   init_charset_table();
   init_hpf_code_table();
   if (!font::load_desc())
-    fatal("sorry, I can't continue");
+    fatal("cannot load 'DESC' description file for device '%1'",
+	  device);
   units_per_inch = font::res;
   hresolution = font::hor;
   vresolution = font::vert;