explain basic mode on initial screen

subiquity/ui/views/welcome.py

@@ -20,9 +20,11 @@ Welcome provides user with language selection
 """
 import logging
 
-from subiquitycore.ui.buttons import forward_btn
+from urwid import Text
+
+from subiquitycore.ui.buttons import forward_btn, other_btn
 from subiquitycore.ui.container import ListBox
-from subiquitycore.ui.utils import screen
+from subiquitycore.ui.utils import button_pile, rewrap, screen
 from subiquitycore.view import BaseView
 
 log = logging.getLogger("subiquity.views.welcome")
@@ -33,6 +35,13 @@ Select the language to use for the installer and to be configured in the
 installed system.
 """)
 
+SERIAL_TEXT = """
+As the installer is running on a serial console, it has started in a
+very basic mode. If you are connecting from a terminal emulator such
+as gnome-terminal that supports unicode and rich colors you can switch
+to "rich mode" which uses colors and supports many languages.
+"""
+
 
 class WelcomeView(BaseView):
     title = "Willkommen! Bienvenue! Welcome! Добро пожаловать! Welkom!"
@@ -40,27 +49,55 @@ class WelcomeView(BaseView):
     def __init__(self, model, controller):
         self.model = model
         self.controller = controller
-        super().__init__(screen(
+        if controller.app.opts.run_on_serial:
-            self._build_model_inputs(),
+            s = self.make_serial_choices()
-            buttons=None,
+        else:
-            narrow_rows=True,
+            s = self.make_language_choices()
-            excerpt=_("Use UP, DOWN and ENTER keys to select your language.")))
+        super().__init__(s)
 
-    def _build_model_inputs(self):
+    def make_language_choices(self):
         btns = []
         current_index = None
         for i, (code, native) in enumerate(self.model.get_languages()):
             if code == self.model.selected_language:
                 current_index = i
-            btns.append(forward_btn(label=native, on_press=self.confirm,
+            btns.append(
+                forward_btn(
+                    label=native,
+                    on_press=self.choose_language,
                     user_arg=code))
 
         lb = ListBox(btns)
         if current_index is not None:
             lb.base_widget.focus_position = current_index
-        return lb
+        return screen(
+            lb, buttons=None, narrow_rows=True,
+            excerpt=_("Use UP, DOWN and ENTER keys to select your language."))
 
-    def confirm(self, sender, code):
+    def make_serial_choices(self):
+        btns = [
+            other_btn(
+                label="Switch to rich mode",
+                on_press=self.enable_rich),
+            forward_btn(
+                label="Continue in basic mode",
+                on_press=self.choose_language,
+                user_arg='C'),
+            ]
+        widgets = [
+            Text(""),
+            Text(rewrap(SERIAL_TEXT)),
+            Text(""),
+            button_pile(btns),
+            ]
+        lb = ListBox(widgets)
+        return screen(lb, buttons=None)
+
+    def enable_rich(self, sender):
+        self.controller.app.toggle_rich()
+        self._w = self.make_language_choices()
+
+    def choose_language(self, sender, code):
         log.debug('WelcomeView %s', code)
         self.controller.done(code)