Map dash-like unicode characters to ASCII dash.k

- Look for the following characters in the input:
  - U+2010 (Hyphen),
  - U+2013 (En Dash)
  - U+2014 (Em Dash)
  - U+2212 (Minus)
  and convert them to:
  - U+002D (ASCII Hyphen-Minus)

- This is not just for appearance. I use an old version of
  Screen which somehow reacts badly to the U+2010 hyphen;
  the terminal becomes seriously corrupt, making the portions
  of a man page adjacent to hyphenated lines unreadable.

2 files changed, 8 insertions, 2 deletions

diff --git a/README.md b/README.md
index 47b8a24..b2184c2 100644
--- a/README.md
+++ b/README.md
@@ -14,6 +14,11 @@ syntax coloring, like what you see `less`.
 Because `mngpr` itself resolves the overstrikes, the resulting rendering
 in Vim is searchable.
 
+Another benefit of `mnpgr` is that it replaces with a plain ASCII dash
+(U+002D) all the nonsense Unicode dashes output by GNU groff.
+This is not just esthetics. In some systems, the U+2010 hyphen 
+seriously corrupts the terminal display, rendering man pages unreadable.
+
 ## Installation
 
 The `mnpgr.vim` file goes into your `~/.vim/syntax` directory, which
diff --git a/mnpgr.tl b/mnpgr.tl
index 46619c9..3256815 100755
--- a/mnpgr.tl
+++ b/mnpgr.tl
@@ -97,7 +97,8 @@
     (with-resources ((rendered-file (path-cat mnpgr-dir `@page.@section.@cols`)
                                     (remove-path rendered-file)))
       (with-stream (s (open-file rendered-file "w"))
-        (let ((ofilt (make-overstrike-filter (lambda (str) (put-string str s)))))
+        (let ((hfilt (op regsub #/[\x2010\x2013\x2014\x2212]/ "-"))
+              (ofilt (make-overstrike-filter (lambda (str) (put-string str s)))))
           (whilet ((line (get-line)))
-            [ofilt line])))
+            (flow line hfilt ofilt))))
       (sh `vim +'@{vim-commands}' '@{rendered-file}' < /dev/tty`))))