04/04: download: Check whether HORIZONTAL ELLIPSIS can be encoded.

[Ludovic Courtès]

civodul pushed a commit to branch master
in repository guix.

commit fde1783087ba93fcadc4b26bd4611ae03626d105
Author: Ludovic Courtès <address@hidden>
Date:   Thu Oct 1 11:28:58 2015 +0200

    download: Check whether HORIZONTAL ELLIPSIS can be encoded.
    
    * guix/build/download.scm (ellipsis): New procedure.
      (store-path-abbreviation): Use it.
---
 guix/build/download.scm |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/guix/build/download.scm b/guix/build/download.scm
index 4b7c53d..240e79e 100644
--- a/guix/build/download.scm
+++ b/guix/build/download.scm
@@ -110,6 +110,13 @@ column."
          (padding    (make-string num-spaces #\space)))
     (string-append left padding right)))
 
+(define* (ellipsis #:optional (port (current-output-port)))
+  "Make a rough guess at whether Unicode's HORIZONTAL ELLIPSIS can be written
+in PORT's encoding, and return either that or ASCII dots."
+  (if (equal? (port-encoding port) "UTF-8")
+      "…"
+      "..."))
+
 (define* (store-path-abbreviation store-path #:optional (prefix-length 6))
   "If STORE-PATH is the file name of a store entry, return an abbreviation of
 STORE-PATH for display, showing PREFIX-LENGTH characters of the hash.
@@ -117,7 +124,7 @@ Otherwise return STORE-PATH."
   (if (string-prefix? (%store-directory) store-path)
       (let ((base (basename store-path)))
         (string-append (string-take base prefix-length)
-                       "…"
+                       (ellipsis)
                        (string-drop base 32)))
       store-path))