- Implement switching from categories to feeds.

- Implement switching between panes back and forth.

App.py

@@ -22,6 +22,22 @@ class Items(urwid.ListBox):
                 idx = idx - 1
                 self.set_focus(idx)
             return
+        elif key in ("l", "right"):
+            focus_widget, idx = self.get_focus()
+            value = next(focus_widget.render((100,), focus=False).content())[1][2].decode().strip()
+            feeds = tui.leftPaneItems[value]["feeds"]
+            feedItems = [urwid.Columns([(4, urwid.Text(item["count"])), urwid.Text(item["name"])])
+                         for item in feeds]
+            walker = urwid.SimpleListWalker([urwid.AttrMap(item, None, 'reveal focus') for item in feedItems])
+            self.body = walker
+            tui.leftBox.set_title(value)
+            return
+        elif key in ("h", "left"):
+            feedItems = tui.feedItems
+            walker = urwid.SimpleListWalker([urwid.AttrMap(item, None, 'reveal focus') for item in feedItems])
+            self.body = walker
+            tui.leftBox.set_title("Categories")
+            return
 
         return super().keypress(size, key)
 
@@ -44,13 +60,24 @@ class TUI(urwid.Frame):
         return tui
 
     def __init__(self):
+
+        self.leftPaneItems = {}
+        self.activePane = False
+        for i in range(0, 15):
+            self.leftPaneItems["Category# " + str(i)] = {"count": str(i),
+                                                         "feeds": [{"count": str(k), "name": "Feed# " + str(k)} for k in range(0, 10)]}
+
         self.executor = ThreadPoolExecutor(max_workers=1)
         self.loop = None
-        self.feedItems = [urwid.Text("Feed# " + str(i)) for i in range(0, 15)]
+        self.feedItems = [urwid.Columns([(4, urwid.Text(self.leftPaneItems[item]["count"])), urwid.Text(item)])
+                          for item in self.leftPaneItems.keys()]
         self.articleItems = [urwid.Text("Article# " + str(i)) for i in range(0, 10)]
         self.feeds = Items(self.feedItems)
         self.articles = Items(self.articleItems)
-        self.container = urwid.Columns([urwid.LineBox(self.feeds, title="Feeds"), urwid.LineBox(self.articles, title="Articles")])
+        self.leftBox = urwid.LineBox(self.feeds, title="Categories")
+        self.container = urwid.Columns(
+            [(40, self.leftBox),
+             urwid.LineBox(self.articles, title="Articles")])
         self.body = self.container
 
         super().__init__(self.body)
@@ -61,7 +88,8 @@ class TUI(urwid.Frame):
 
     def unhandled_input(self, key):
         if key == "tab":
-            self.container.set_focus(1)
+            self.activePane = not self.activePane
+            self.container.set_focus(int(self.activePane))
         elif key == "q":
             raise urwid.ExitMainLoop()