docs and refactor

examples/markdown.py

@@ -0,0 +1,41 @@
+from textual.app import App, ComposeResult
+from textual.reactive import var
+from textual.widgets import Footer, MarkdownViewer
+
+
+class MarkdownApp(App):
+    BINDINGS = [
+        ("t", "toggle_toc", "TOC"),
+        ("b", "back", "Back"),
+        ("f", "forward", "Forward"),
+    ]
+
+    path = var("demo.md")
+
+    @property
+    def markdown_viewer(self) -> MarkdownViewer:
+        """Get the Markdown widget."""
+        return self.query_one(MarkdownViewer)
+
+    def compose(self) -> ComposeResult:
+        yield Footer()
+        yield MarkdownViewer()
+
+    async def on_mount(self) -> None:
+        self.markdown_viewer.focus()
+        if not await self.markdown_viewer.go(self.path):
+            self.exit(message=f"Unable to load {self.path!r}")
+
+    def action_toggle_toc(self) -> None:
+        self.markdown_viewer.show_toc = not self.markdown_viewer.show_toc
+
+    async def action_back(self) -> None:
+        await self.markdown_viewer.back()
+
+    async def action_forward(self) -> None:
+        await self.markdown_viewer.forward()
+
+
+if __name__ == "__main__":
+    app = MarkdownApp()
+    app.run()