[bug#65546] [PATCH v2] guix: Properly compute progress bar width.

[Julien Lepiller <julien@lepiller.eu>]

* guix/build/syscalls.scm (terminal-width): New procedure.
* guix/progress.scm (progress-reporter/bar): Use it to compute progress
bar width.
* guix/git.scm (show-progress): Use it to compute progress bar width.
* tests/syscalls.scm: Add tests.
---
 guix/build/syscalls.scm | 24 ++++++++++++++++++++++++
 guix/git.scm            |  4 +++-
 guix/progress.scm       |  5 ++++-
 tests/syscalls.scm      |  6 ++++++
 4 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/guix/build/syscalls.scm b/guix/build/syscalls.scm
index d947b010d3..a1365cc68c 100644
--- a/guix/build/syscalls.scm
+++ b/guix/build/syscalls.scm
@@ -192,6 +192,7 @@ (define-module (guix build syscalls)
             terminal-window-size
             terminal-columns
             terminal-rows
+            terminal-string-width
             openpty
             login-tty
 
@@ -2335,6 +2336,29 @@ (define* (terminal-rows #:optional (port (current-output-port)))
 always a positive integer."
   (terminal-dimension window-size-rows port (const 25)))
 
+(define get-wchar-ffi
+  (pointer->procedure int
+                      (dynamic-func "mbstowcs" (dynamic-link))
+                      (list '* '* size_t)))
+(define terminal-string-width-ffi
+  (pointer->procedure int
+                      (dynamic-func "wcswidth" (dynamic-link))
+                      (list '* size_t)))
+
+(define (terminal-string-width str)
+  "Return the width of a string as it would be printed on the terminal.  This
+procedure accounts for characters that have a different width than 1, such as
+CJK double-width characters."
+  (define (get-wchar str)
+    (let ((wchar (make-bytevector (* (+ (string-length str) 1) 4))))
+      (get-wchar-ffi (bytevector->pointer wchar)
+                     (string->pointer str)
+                     (string-length str))
+      wchar))
+  (terminal-string-width-ffi
+    (bytevector->pointer (get-wchar str))
+    (string-length str)))
+
 (define openpty
   (let ((proc (syscall->procedure int "openpty" '(* * * * *)
                                   #:library "libutil")))
diff --git a/guix/git.scm b/guix/git.scm
index 1cb87a4560..728b761e62 100644
--- a/guix/git.scm
+++ b/guix/git.scm
@@ -29,6 +29,8 @@ (define-module (guix git)
   #:use-module (gcrypt hash)
   #:use-module ((guix build utils)
                 #:select (mkdir-p delete-file-recursively))
+  #:use-module ((guix build syscalls)
+                #:select (terminal-string-width))
   #:use-module (guix store)
   #:use-module (guix utils)
   #:use-module (guix records)
@@ -153,7 +155,7 @@ (define %
   ;; TODO: Both should be handled & exposed by the PROGRESS-BAR API instead.
   (define width
     (max (- (current-terminal-columns)
-            (string-length label) 7)
+            (terminal-string-width label) 7)
          3))
 
   (define grain
diff --git a/guix/progress.scm b/guix/progress.scm
index 33cf6f4a1a..e7cf7e168a 100644
--- a/guix/progress.scm
+++ b/guix/progress.scm
@@ -21,9 +21,12 @@
 
 (define-module (guix progress)
   #:use-module (guix records)
+  #:use-module ((guix build syscalls)
+                #:select (terminal-string-width))
   #:use-module (srfi srfi-19)
   #:use-module (rnrs io ports)
   #:use-module (rnrs bytevectors)
+  #:use-module (system foreign)
   #:use-module (ice-9 format)
   #:use-module (ice-9 match)
   #:export (<progress-reporter>
@@ -307,7 +310,7 @@ (define (draw-bar)
       (if (string-null? prefix)
           (display (progress-bar ratio (current-terminal-columns)) port)
           (let ((width (- (current-terminal-columns)
-                          (string-length prefix) 3)))
+                          (terminal-string-width prefix) 3)))
             (display prefix port)
             (display "  " port)
             (display (progress-bar ratio width) port)))
diff --git a/tests/syscalls.scm b/tests/syscalls.scm
index c9e011f453..eb85b358c4 100644
--- a/tests/syscalls.scm
+++ b/tests/syscalls.scm
@@ -583,6 +583,12 @@ (define perform-container-tests?
 (test-assert "terminal-rows"
   (> (terminal-rows) 0))
 
+(test-assert "terminal-string-width English"
+  (= (terminal-string-width "hello") 5))
+
+(test-assert "terminal-string-width Japanese"
+  (= (terminal-string-width "今日は") 6))
+
 (test-assert "openpty"
   (let ((head inferior (openpty)))
     (and (integer? head) (integer? inferior)
-- 
2.41.0