Added dyanmic bindings to Markdown

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+## [0.62.0] - Unrelease
+
+### Added
+
+- Added `start` and `end` properties to Markdown Navigator
+
 ## [0.61.1] - 2024-05-19
 
 ### Fixed

examples/markdown.py

@@ -31,6 +31,9 @@ async def on_mount(self) -> None:
         except FileNotFoundError:
             self.exit(message=f"Unable to load {self.path!r}")
 
+    def on_markdown_viewer_navigator_updated(self) -> None:
+        self.refresh_bindings()
+
     def action_toggle_table_of_contents(self) -> None:
         self.markdown_viewer.show_table_of_contents = (
             not self.markdown_viewer.show_table_of_contents
@@ -42,6 +45,13 @@ async def action_back(self) -> None:
     async def action_forward(self) -> None:
         await self.markdown_viewer.forward()
 
+    def check_action(self, action: str, parameters: tuple[object, ...]) -> bool | None:
+        if action == "forward" and self.markdown_viewer.navigator.end:
+            return None
+        if action == "back" and self.markdown_viewer.navigator.start:
+            return None
+        return True
+
 
 if __name__ == "__main__":
     app = MarkdownApp()

src/textual/widgets/_markdown.py

@@ -48,6 +48,16 @@ def location(self) -> Path:
             return Path(".")
         return self.stack[self.index]
 
+    @property
+    def start(self) -> bool:
+        """Is the current location at the start of the stack?"""
+        return self.index == 0
+
+    @property
+    def end(self) -> bool:
+        """Is the current location at the end of the stack?"""
+        return self.index >= len(self.stack) - 1
+
     def go(self, path: str | PurePath) -> Path:
         """Go to a new document.
 
@@ -1066,6 +1076,9 @@ class MarkdownViewer(VerticalScroll, can_focus=True, can_focus_children=True):
 
     navigator: var[Navigator] = var(Navigator)
 
+    class NavigatorUpdated(Message):
+        """Navigator has been changed (clicked link etc)."""
+
     def __init__(
         self,
         markdown: str | None = None,
@@ -1114,16 +1127,19 @@ async def go(self, location: str | PurePath) -> None:
         else:
             # We've been asked to go to a file, optionally with an anchor.
             await self.document.load(self.navigator.go(location))
+            self.post_message(self.NavigatorUpdated())
 
     async def back(self) -> None:
         """Go back one level in the history."""
         if self.navigator.back():
             await self.document.load(self.navigator.location)
+            self.post_message(self.NavigatorUpdated())
 
     async def forward(self) -> None:
         """Go forward one level in the history."""
         if self.navigator.forward():
             await self.document.load(self.navigator.location)
+            self.post_message(self.NavigatorUpdated())
 
     async def _on_markdown_link_clicked(self, message: Markdown.LinkClicked) -> None:
         message.stop()