40/67: installer: keymap: Do not fail on non-kmscon terminals.

[guix-commits]

civodul pushed a commit to branch wip-newt-installer
in repository guix.

commit 4ecb1440126f23d9d4809922f82bb23e4599de71
Author: Mathieu Othacehe <address@hidden>
Date:   Wed Dec 5 21:53:40 2018 +0900

    installer: keymap: Do not fail on non-kmscon terminals.
    
    kmscon-update-keymap fails on non kmscon terminals because KEYMAP_UPDATE
    environment variable is not defined. As it is convenient to test the 
installer
    on a regular terminal, do nothing if KEYMAP_UPDATE is missing.
    
    * gnu/installer/keymap.scm (kmscon-update-keymap): Do nothing if 
KEYMAP_UPDATE
    is not defined.
---
 gnu/installer/keymap.scm | 36 +++++++++++++++++++++---------------
 1 file changed, 21 insertions(+), 15 deletions(-)

diff --git a/gnu/installer/keymap.scm b/gnu/installer/keymap.scm
index d9f8656..d66b376 100644
--- a/gnu/installer/keymap.scm
+++ b/gnu/installer/keymap.scm
@@ -149,18 +149,24 @@ Configuration Database, describing possible XKB 
configurations."
        (values models layouts)))))
 
 (define (kmscon-update-keymap model layout variant)
-  (let ((keymap-file (getenv "KEYMAP_UPDATE")))
-    (unless (and keymap-file
-                 (file-exists? keymap-file))
-      (error "Unable to locate keymap update file"))
-
-    (call-with-output-file keymap-file
-        (lambda (port)
-          (format port model)
-          (put-u8 port 0)
-
-          (format port layout)
-          (put-u8 port 0)
-
-          (format port variant)
-          (put-u8 port 0)))))
+  "Update kmscon keymap with the provided MODEL, LAYOUT and VARIANT."
+  (and=>
+   (getenv "KEYMAP_UPDATE")
+   (lambda (keymap-file)
+     (unless (file-exists? keymap-file)
+       (error "Unable to locate keymap update file"))
+
+     ;; See file gnu/packages/patches/kmscon-runtime-keymap-switch.patch.
+     ;; This dirty hack makes possible to update kmscon keymap at runtime by
+     ;; writing an X11 keyboard model, layout and variant to a named pipe
+     ;; referred by KEYMAP_UPDATE environment variable.
+     (call-with-output-file keymap-file
+       (lambda (port)
+         (format port model)
+         (put-u8 port 0)
+
+         (format port layout)
+         (put-u8 port 0)
+
+         (format port variant)
+         (put-u8 port 0))))))