core/boxes: Improve handling of pressing Esc during message compose.

Fixes zulip#1342.

zulipterminal/core.py

@@ -523,6 +523,22 @@ def stream_muting_confirmation_popup(
         mute_this_stream = partial(self.model.toggle_stream_muted_status, stream_id)
         self.loop.widget = PopUpConfirmationView(self, question, mute_this_stream)
 
+    def exit_compose_confirmation_popup(self) -> None:
+        question = urwid.Text(
+            (
+                "bold",
+                "Please confirm that you wish to exit the compose box. "
+                "(You can save the message as a draft upon returning to compose)",
+            ),
+            "center",
+        )
+        write_box = self.view.write_box
+        popup_view = PopUpConfirmationView(
+            self, question, write_box.exit_compose_box, location="center"
+        )
+        self.loop.widget = popup_view
+        self.loop.run()
+
     def copy_to_clipboard(self, text: str, text_category: str) -> None:
         try:
             pyperclip.copy(text)

zulipterminal/ui_tools/boxes.py

@@ -710,6 +710,12 @@ def autocomplete_emojis(
 
         return emoji_typeahead, emojis
 
+    def exit_compose_box(self) -> None:
+        self._set_compose_attributes_to_defaults()
+        self.view.controller.exit_editor_mode()
+        self.main_view(False)
+        self.view.middle_column.set_focus("body")
+
     def keypress(self, size: urwid_Size, key: str) -> Optional[str]:
         if self.is_in_typeahead_mode and not (
             is_command_key("AUTOCOMPLETE", key)
@@ -801,6 +807,8 @@ def keypress(self, size: urwid_Size, key: str) -> Optional[str]:
                     )
         elif is_command_key("GO_BACK", key):
             self.send_stop_typing_status()
+            if len(self.msg_write_box.edit_text) > 10:
+                self.view.controller.exit_compose_confirmation_popup()
             self._set_compose_attributes_to_defaults()
             self.view.controller.exit_editor_mode()
             self.main_view(False)