installer: Warn about hardware support after the welcome page.

This is a followup to 682639c107, which
added the uvesafb upfront, before welcome page had been displayed.

* gnu/installer/newt/welcome.scm (check-hardware-support): New
procedure.
(run-welcome-page): Use it.

gnu/installer/newt/welcome.scm

@@ -1,6 +1,6 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2018 Mathieu Othacehe <m.othacehe@gmail.com>
-;;; Copyright © 2020 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2020, 2022 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2022 Florian Pelz <pelzflorian@pelzflorian.de>
 ;;;
 ;;; This file is part of GNU Guix.
@@ -121,55 +121,58 @@ (define (choice->item str)
         (lambda ()
           (destroy-form-and-pop form))))))
 
-(define (run-welcome-page logo)
+(define (check-hardware-support)
-  "Run a welcome page with the given textual LOGO displayed at the center of
+  "Warn about unsupported devices."
-the page. Ask the user to choose between manual installation, graphical
+  (when (member "uvesafb" (modules-loaded))
-installation and reboot."
+    (run-error-page (G_ "\
-  (begin
-    (when (member "uvesafb" (modules-loaded))
-      (run-error-page (G_ "\
 This may be a false alarm, but possibly your graphics hardware does not
 work well with only free software.  Expect trouble.  If after installation,
 the system does not boot, perhaps you will need to add nomodeset to the
 kernel arguments and need to configure the uvesafb kernel module.")
-                      (G_ "Pre-install warning")))
+                    (G_ "Pre-install warning"))))
-    (when (file-exists? %core-dump)
+
-      (match
+(define (run-welcome-page logo)
-          (choice-window
+  "Run a welcome page with the given textual LOGO displayed at the center of
-           (G_ "Previous installation failed")
+the page. Ask the user to choose between manual installation, graphical
-           (G_ "Continue")
+installation and reboot."
-           (G_ "Report the failure")
+  (when (file-exists? %core-dump)
-           (G_ "It seems that the previous installation exited unexpectedly \
+    (match (choice-window
+            (G_ "Previous installation failed")
+            (G_ "Continue")
+            (G_ "Report the failure")
+            (G_ "It seems that the previous installation exited unexpectedly \
 and generated a core dump.  Do you want to continue or to report the failure \
 first?"))
-        (1 #t)
+      (1 #t)
-        (2 (raise
+      (2 (raise
-            (condition
+          (condition
-             (&user-abort-error))))))
+           (&user-abort-error))))))
-    (run-menu-page
+
-     (G_ "GNU Guix install")
+  (run-menu-page
-     (G_ "Welcome to GNU Guix system installer!
+   (G_ "GNU Guix install")
+   (G_ "Welcome to GNU Guix system installer!
 
 You will be guided through a graphical installation program.
 
 If you are familiar with GNU/Linux and you want tight control over \
 the installation process, you can instead choose manual installation.  \
 Documentation is accessible at any time by pressing Ctrl-Alt-F2.")
-     logo
+   logo
-     #:listbox-items
+   #:listbox-items
-     `((,(G_ "Graphical install using a terminal based interface")
+   `((,(G_ "Graphical install using a terminal based interface")
-        .
+      .
-        ,(const #t))
+      ,check-hardware-support)
-       (,(G_ "Install using the shell based process")
+     (,(G_ "Install using the shell based process")
-        .
+      .
-        ,(lambda ()
+      ,(lambda ()
-           ;; Switch to TTY3, where a root shell is available for shell based
+         (check-hardware-support)
-           ;; install. The other root TTY's would have been ok too.
+         ;; Switch to TTY3, where a root shell is available for shell based
-           (system* "chvt" "3")
+         ;; install. The other root TTY's would have been ok too.
-           (run-welcome-page logo)))
+         (system* "chvt" "3")
-       (,(G_ "Reboot")
+         (run-welcome-page logo)))
-        .
+     (,(G_ "Reboot")
-        ,(lambda ()
+      .
-           (newt-finish)
+      ,(lambda ()
-           (reboot))))
+         (newt-finish)
-     #:listbox-item->text car)))
+         (reboot))))
+   #:listbox-item->text car))