ui/views: Use bold column title for consistency with LineBox border.

This commit passes a title_attribute to the LineBox widget for
column titles which improves consistency with the surrounding LineBox
borders and also helps in emphasizing the titles with respect to
the text below.

Author: zee-bit

zulipterminal/ui.py

@@ -47,14 +47,16 @@ def left_column_view(self) -> Any:
     def middle_column_view(self) -> Any:
         self.middle_column = MiddleColumnView(self, self.model, self.write_box,
                                               self.search_box)
-        return urwid.LineBox(self.middle_column, title='Messages',
+        return urwid.LineBox(self.middle_column,
+                             title='Messages', title_attr='column_title',
                              tline=LIST_TITLE_BAR_LINE,
                              bline='', trcorner='│', tlcorner='│')
 
     def right_column_view(self) -> Any:
         self.users_view = RightColumnView(View.RIGHT_WIDTH, self)
         return urwid.LineBox(
-            self.users_view, title="Users",
+            self.users_view,
+            title="Users", title_attr='column_title',
             tlcorner=LIST_TITLE_BAR_LINE,
             tline=LIST_TITLE_BAR_LINE,
             trcorner=LIST_TITLE_BAR_LINE,

zulipterminal/ui_tools/views.py

@@ -805,7 +805,8 @@ def streams_view(self) -> Any:
 
         self.view.stream_w = StreamsView(streams_btn_list, self.view)
         w = urwid.LineBox(
-            self.view.stream_w, title="Streams",
+            self.view.stream_w,
+            title="Streams", title_attr='column_title',
             tlcorner=LIST_TITLE_BAR_LINE,
             tline=LIST_TITLE_BAR_LINE,
             trcorner=LIST_TITLE_BAR_LINE,
@@ -832,7 +833,8 @@ def topics_view(self, stream_button: Any) -> Any:
         self.view.topic_w = TopicsView(topics_btn_list, self.view,
                                        stream_button)
         w = urwid.LineBox(
-            self.view.topic_w, title="Topics",
+            self.view.topic_w,
+            title="Topics", title_attr='column_title',
             tlcorner=LIST_TITLE_BAR_LINE,
             tline=LIST_TITLE_BAR_LINE,
             trcorner=LIST_TITLE_BAR_LINE,