core/ui: Add UI elements to markdown help view on toggling.

This commit adds:
 * member function show_markdown_help() to trigger the popup.
 * keypress event in `ui.py` to trigger the popup.

Fixes zulip#623.

Author: Ezio-Sarthak

zulipterminal/core.py

@@ -24,6 +24,7 @@
     EditHistoryView,
     EditModeView,
     HelpView,
+    MarkdownHelpView,
     MsgInfoView,
     NoticeView,
     PopUpConfirmationView,
@@ -239,6 +240,12 @@ def show_help(self) -> None:
         help_view = HelpView(self, "Help Menu (up/down scrolls)")
         self.show_pop_up(help_view, "area:help")
 
+    def show_markdown_help(self) -> None:
+        markdown_view = MarkdownHelpView(
+            self, "Markdown Help Menu (up/down scrolls)", self.model.server_url
+        )
+        self.show_pop_up(markdown_view, "area:help")
+
     def show_topic_edit_mode(self, button: Any) -> None:
         self.show_pop_up(EditModeView(self, button), "area:msg")
 

zulipterminal/ui.py

@@ -274,6 +274,10 @@ def keypress(self, size: urwid_Box, key: str) -> Optional[str]:
             # Show help menu
             self.controller.show_help()
             return key
+        elif is_command_key("MARKDOWN_HELP", key):
+            # Show markdown help menu
+            self.controller.show_markdown_help()
+            return key
         # replace alternate keys with arrow/functional keys
         # This is needed for navigating in widgets
         # other than message_view.