ui: Make ZT go to into autohide mode if terminal is small.

This commit makes ZT go into autohide mode when terminal width is
smaller than MINNORMALWIDTH. This makes the ZT more readable in a
small terminal.

To do so this makes use of urwid's render method to get maxcols, a
Literal `self.mode` which takes values "small", "normal" and "wide"
and existing `show_left_panel` and `show_right_panel` methods with
small changes.

Author: Rohitth007

zulipterminal/ui.py

@@ -5,6 +5,7 @@
 from typing import Any, List, Optional
 
 import urwid
+from typing_extensions import Literal
 
 from zulipterminal.config.keys import commands_for_random_tips, is_command_key
 from zulipterminal.config.symbols import (
@@ -21,6 +22,9 @@
 from zulipterminal.urwid_types import urwid_Box
 
 
+MINNORMALWIDTH = 103
+
+
 class View(urwid.WidgetWrap):
     """
     A class responsible for providing the application's interface.
@@ -42,6 +46,7 @@ def __init__(self, controller: Any) -> None:
 
         self.message_view: Any = None
         self.displaying_selection_hint = False
+        self.mode: Literal["small", "normal", "wide"] = "normal"
 
         super().__init__(self.main_window())
 
@@ -176,16 +181,16 @@ def main_window(self) -> Any:
         )
         return w
 
-    def show_left_panel(self, *, visible: bool) -> None:
-        if not self.autohide:
+    def show_left_panel(self, *, visible: bool, ignore_check: bool = False) -> None:
+        if not self.autohide and self.mode != "small" and not ignore_check:
             return
         option = ("given", self.LEFT_WIDTH) if visible else ("given", 0)
         self.body.contents[0] = (self.left_panel, self.body.options(*option))
         if visible:
             self.body.focus_position = 0
 
-    def show_right_panel(self, *, visible: bool) -> None:
-        if not self.autohide:
+    def show_right_panel(self, *, visible: bool, ignore_check: bool = False) -> None:
+        if not self.autohide and self.mode != "small" and not ignore_check:
             return
         option = ("given", self.RIGHT_WIDTH) if visible else ("given", 0)
         self.body.contents[2] = (self.right_panel, self.body.options(*option))
@@ -314,6 +319,25 @@ def mouse_event(
 
         return super().mouse_event(size, event, button, col, row, focus)
 
+    def render(self, size: urwid_Box, focus: bool) -> Any:
+        maxcols, maxrows = size
+
+        if not self.autohide:
+            if maxcols < MINNORMALWIDTH and self.mode != "small":
+                self.mode = "small"
+                if self.body.focus_position == 2:
+                    self.show_left_panel(visible=False)
+                else:
+                    self.show_right_panel(visible=False)
+            elif maxcols >= MINNORMALWIDTH and self.mode != "normal":
+                self.mode = "normal"
+                prev_focus = self.body.focus_position
+                self.show_right_panel(visible=True, ignore_check=True)
+                self.show_left_panel(visible=True, ignore_check=True)
+                self.body.focus_position = prev_focus
+
+        return super().render(size, focus)
+
 
 class Screen(urwid.raw_display.Screen):
     def write(self, data: Any) -> None: