Made arrow keys and mouse wheel work in the help page.

BUGS

@@ -1,5 +1,4 @@
 Current
-- Scrolling in the help screen doesn't work with the arrow keys.
 - Within the sandbox sudo is not working for tools.
 
 
@@ -210,6 +209,7 @@ Fixed
 - Some jobs are always recalculated when restarting vigil.
   e.g. vigil.py pylint, BUGS metadata, BUGS _pygments
 - Tracebacks occur if you pause during early startup.
+- Scrolling in the help screen doesn't work with the arrow keys.
 
 
 Won't fix

vigil

@@ -529,6 +529,14 @@ def _get_help_text(is_status_simple=True):
                        meaning for status, meaning in tools.STATUS_MEANINGS])
 
 
+def _make_key_map(key_data):
+    key_map = {}
+    for keys, action in key_data:
+        for key in keys:
+            key_map[key] = action
+    return key_map
+
+
 class Help:
 
     def __init__(self, summary, screen):
@@ -538,20 +546,34 @@ class Help:
         self.view = fill3.View.from_widget(self.body)
         self.widget = fill3.Border(self.view, title="Help")
         portal = self.view.portal
-        self.key_map = {"h": self.exit_help, "d": portal.scroll_up,
-                        "c": portal.scroll_down, "j": portal.scroll_left,
-                        "k": portal.scroll_right, "q": self.exit_help}
+        self.key_map = _make_key_map([
+            ({"h"}, self.exit_help), ({"d", "up"}, portal.scroll_up),
+            ({"c", "down"}, portal.scroll_down),
+            ({"j", "left"}, portal.scroll_left),
+            ({"k", "right"}, portal.scroll_right), ({"q"}, self.exit_help)])
 
     def exit_help(self):
         self.screen._is_help_visible = False
 
-    def on_input_event(self, event):
+    def on_mouse_event(self, event, appearance_changed_event):
+        if event[1] == 4:  # Mouse wheel up
+            self.view.portal.scroll_up()
+            appearance_changed_event.set()
+        elif event[1] == 5:  # Mouse wheel down
+            self.view.portal.scroll_down()
+            appearance_changed_event.set()
+
+    def on_input_event(self, event, appearance_changed_event):
+        if type(event) == tuple:
+            self.on_mouse_event(event, appearance_changed_event)
+            return
         try:
             action = self.key_map[event]
         except KeyError:
             pass
         else:
             action()
+            appearance_changed_event.set()
 
     def appearance(self, dimensions):
         text = _get_help_text(self.summary.is_status_simple)
@@ -582,7 +604,7 @@ class Screen:
         self._is_help_visible = False
         self._is_paused = False
         self._make_widgets()
-        self._make_keymap()
+        self._key_map = _make_key_map(Screen._KEY_DATA)
 
     def _partition(self, widgets, height):
         smaller_height = max(height // 4, 10)
@@ -608,13 +630,6 @@ class Screen:
         land_no_log = fill3.Column([summary, self._listing], self._partition_2)
         self._layouts = [[land_no_log, port_no_log], [land_log, port_log]]
 
-    def _make_keymap(self):
-        key_map = {}
-        for keys, action in self._KEY_DATA:
-            for key in keys:
-                key_map[key] = action
-        self._key_map = key_map
-
     def toggle_help(self):
         self._is_help_visible = not self._is_help_visible
 
@@ -729,8 +744,8 @@ class Screen:
 
     def on_input_event(self, event):
         if self._is_help_visible:
-            self._help_widget.on_input_event(event)
-            self._appearance_changed_event.set()
+            self._help_widget.on_input_event(
+                event, self._appearance_changed_event)
             return
         if type(event) == tuple:
             self.on_mouse_event(event)