Keep parsed Markdown in transcript ranges; restore the reader's place

src/toad/block_content.py

@@ -1,12 +1,24 @@
-"""Nominal selection capabilities on the actual mounted block widgets."""
+"""Declared block capabilities shared by scene and original source consumers."""
 from collections.abc import Iterable
+from functools import cached_property
+
+from textual.widgets import _markdown as native_markdown
 
 from toad.menus import MenuItem
 
 
 class BlockContent:
     """Non-interactive blocks inherit empty content and expansion behavior."""
 
+    def retain_transcript_source(self, fragment):
+        """Native content without acquired Markdown has no source to transfer."""
+
+    @cached_property
+    def block_cursor(self):
+        from toad.block_navigation import AtomicBlockCursor
+
+        return AtomicBlockCursor(self)
+
     def get_block_menu(self) -> Iterable[MenuItem]:
         return ()
 
@@ -30,13 +42,134 @@ def collapse_block(self) -> None:
 
 
 class MarkdownBlockContent(BlockContent):
-    """Textual's Markdown block factory admits these capabilities once."""
+    """Declared native blocks share source-copy and menu capabilities."""
 
-    def get_clipboard_text(self) -> str:
-        return self.source
+    code: str | None = None
+
+    @classmethod
+    def clipboard_source(cls, markdown: str | None, code: str | None) -> str | None:
+        return markdown
+
+    @classmethod
+    def prompt_source(cls, markdown: str | None, code: str | None) -> str | None:
+        return cls.clipboard_source(markdown, code)
 
     @classmethod
-    def declare(cls, external: type) -> type:
-        # Keep Textual's existing token catalog and concrete rendering classes.
-        # The mounted class itself owns the capability, without a widget wrapper.
-        return type(external.__name__, (cls, external), {"__module__": __name__})
+    def source_block_menu(cls, source) -> Iterable[MenuItem]:
+        # A scene menu may depend on actual controls. It must explicitly
+        # declare source behavior before detached consumers can supply it.
+        cls._require_document_methods({"get_block_menu": BlockContent.get_block_menu})
+        return ()
+
+    @classmethod
+    def source_copy(cls, source, *, prompt: bool = False) -> str | None:
+        cls._require_document_methods({
+            "get_clipboard_text": MarkdownBlockContent.get_clipboard_text,
+            "get_prompt_text": MarkdownBlockContent.get_prompt_text,
+        })
+        supply = cls.prompt_source if prompt else cls.clipboard_source
+        return supply(source.source_text(), source.code)
+
+    def get_clipboard_text(self) -> str | None:
+        return self.clipboard_source(self.source, self.code)
+
+    def get_prompt_text(self) -> str | None:
+        return self.prompt_source(self.source, self.code)
+
+    @classmethod
+    def blocks_for(cls, catalog: dict[str, type]) -> dict[str, type]:
+        """Extend the original token catalog through declared inheritance.
+
+        The native owner decides which token selects which block. These
+        declarations add capabilities and stable Python identities; neither
+        token names nor a transport codec select an implementation here.
+        """
+        native = set(catalog.values())
+        implementations = {}
+        for declaration in cls.__subclasses__():
+            for base in declaration.__bases__:
+                if base in native:
+                    if base in implementations:
+                        raise TypeError(f"Multiple declared block extensions for {base.__name__}")
+                    implementations[base] = declaration
+        return {token: implementations[block] for token, block in catalog.items()}
+
+
+class MarkdownH1(MarkdownBlockContent, native_markdown.MarkdownH1):
+    pass
+
+
+class MarkdownH2(MarkdownBlockContent, native_markdown.MarkdownH2):
+    pass
+
+
+class MarkdownH3(MarkdownBlockContent, native_markdown.MarkdownH3):
+    pass
+
+
+class MarkdownH4(MarkdownBlockContent, native_markdown.MarkdownH4):
+    pass
+
+
+class MarkdownH5(MarkdownBlockContent, native_markdown.MarkdownH5):
+    pass
+
+
+class MarkdownH6(MarkdownBlockContent, native_markdown.MarkdownH6):
+    pass
+
+
+class MarkdownHorizontalRule(MarkdownBlockContent, native_markdown.MarkdownHorizontalRule):
+    pass
+
+
+class MarkdownParagraph(MarkdownBlockContent, native_markdown.MarkdownParagraph):
+    pass
+
+
+class MarkdownBlockQuote(MarkdownBlockContent, native_markdown.MarkdownBlockQuote):
+    pass
+
+
+class MarkdownBulletList(MarkdownBlockContent, native_markdown.MarkdownBulletList):
+    pass
+
+
+class MarkdownOrderedList(MarkdownBlockContent, native_markdown.MarkdownOrderedList):
+    pass
+
+
+class MarkdownOrderedListItem(MarkdownBlockContent, native_markdown.MarkdownOrderedListItem):
+    pass
+
+
+class MarkdownUnorderedListItem(MarkdownBlockContent, native_markdown.MarkdownUnorderedListItem):
+    pass
+
+
+class MarkdownTable(MarkdownBlockContent, native_markdown.MarkdownTable):
+    pass
+
+
+class MarkdownTBody(MarkdownBlockContent, native_markdown.MarkdownTBody):
+    pass
+
+
+class MarkdownTHead(MarkdownBlockContent, native_markdown.MarkdownTHead):
+    pass
+
+
+class MarkdownTR(MarkdownBlockContent, native_markdown.MarkdownTR):
+    pass
+
+
+class MarkdownTH(MarkdownBlockContent, native_markdown.MarkdownTH):
+    pass
+
+
+class MarkdownTD(MarkdownBlockContent, native_markdown.MarkdownTD):
+    pass
+
+
+class MarkdownFence(MarkdownBlockContent, native_markdown.MarkdownFence):
+    pass