installer: Add a help page.

* gnu/installer/newt/help.scm: New file.
* gnu/local.mk (INSTALLER_MODULES): Add it.
* po/guix/POTFILES.in: Add it.
* gnu/installer/record.scm (<installer>): Add 'help-menu' and 'help-page'
 fields,
 (installer-help-menu, installer-help-page): new exported procedures.
 * gnu/installer/newt.scm (init): Set the help line,
 (help-menu, help-page): new procedures used ...
 (newt-installer): ... here.
 * gnu/installer/newt/keymap.scm (run-layout-page): Add a context argument to
 differenciate the help context from the main one,
 (run-keymap-page): add a context argument and pass it to run-layout-page.
 * gnu/installer.scm (compute-keymap-step): Add a context argument and pass it
 to 'installer-keymap-page',
 (installer-steps): set the help menu and pass the appropriate context to
 compute-keymap-step calls,
 (guile-newt): update to revision 2.

2 files changed, 66 insertions, 10 deletions

diff --git a/gnu/installer/newt/help.scm b/gnu/installer/newt/help.scm
new file mode 100644
index 0000000000..8d85832dc8
--- /dev/null
+++ b/gnu/installer/newt/help.scm
@@ -0,0 +1,43 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2020 Mathieu Othacehe <m.othacehe@gmail.com>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (gnu installer newt help)
+  #:use-module (gnu installer steps)
+  #:use-module (gnu installer newt page)
+  #:use-module (guix i18n)
+  #:use-module (ice-9 match)
+  #:use-module (newt)
+  #:export (run-help-page))
+
+(define (run-help-page keyboard-layout-selection)
+  "Run a help page allowing to change the keyboard layout"
+  (let* ((items
+          (list
+           (cons (G_ "Change keyboard layout") keyboard-layout-selection)))
+         (result
+          (run-listbox-selection-page
+           #:info-text (G_ "This is the help menu, please choose an action.")
+           #:title (G_ "Installation help")
+           #:listbox-items items
+           #:listbox-item->text car
+           #:sort-listbox-items? #f
+           #:button-text (G_ "Continue"))))
+    (match result
+      ((_ . proc)
+       (proc))
+      (_ #f))))
diff --git a/gnu/installer/newt/keymap.scm b/gnu/installer/newt/keymap.scm
index 2908ba7f0e..0147a0b9d5 100644
--- a/gnu/installer/newt/keymap.scm
+++ b/gnu/installer/newt/keymap.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2018 Mathieu Othacehe <m.othacehe@gmail.com>
+;;; Copyright © 2018, 2020 Mathieu Othacehe <m.othacehe@gmail.com>
 ;;; Copyright © 2019 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
@@ -33,20 +33,32 @@
   #:export (run-keymap-page
             keyboard-layout->configuration))
 
-(define (run-layout-page layouts layout->text)
+(define (run-layout-page layouts layout->text context)
   (let ((title (G_ "Layout")))
     (run-listbox-selection-page
      #:title title
-     #:info-text (G_ "Please choose your keyboard layout.")
+     #:info-text
+     (case context
+       ((help) (G_ "Please choose your keyboard layout. \
+It will only be used during the installation process."))
+       (else (G_ "Please choose your keyboard layout. \
+It will be used during the install process, and for the installed system. \
+You can switch to different layout at any time from the help menu.")))
      #:listbox-items layouts
      #:listbox-item->text layout->text
      #:sort-listbox-items? #f
-     #:button-text (G_ "Exit")
+     #:button-text
+     (case context
+       ((help) (G_ "Continue"))
+       (else (G_ "Exit")))
      #:button-callback-procedure
-     (lambda _
-       (raise
-        (condition
-         (&installer-step-abort)))))))
+     (case context
+       ((help) (const #t))
+       (else
+        (lambda _
+          (raise
+           (condition
+            (&installer-step-abort)))))))))
 
 (define (run-variant-page variants variant->text)
   (let ((title (G_ "Variant")))
@@ -100,7 +112,7 @@
          variants))
     (cut append <> <>)))
 
-(define* (run-keymap-page layouts)
+(define* (run-keymap-page layouts #:key (context #f))
   "Run a page asking the user to select a keyboard layout and variant. LAYOUTS
 is a list of supported X11-KEYMAP-LAYOUT. Return a list of two elements, the
 names of the selected keyboard layout and variant."
@@ -114,7 +126,8 @@ names of the selected keyboard layout and variant."
           (sort-layouts layouts)
           (lambda (layout)
             (gettext (x11-keymap-layout-description layout)
-                     "xkeyboard-config"))))))
+                     "xkeyboard-config"))
+          context))))
      ;; Propose the user to select a variant among those supported by the
      ;; previously selected layout.
      (installer-step