Merge pull request #5950 from Textualize/markdown-stream

WIP Markdown streaming

Author: willmcgugan

CHANGELOG.md

@@ -6,12 +6,21 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 
-## [3.7.2] - Unreleased
+## Unreleased
 
 ### Fixed
 
 - Fixed `query_one` and `query_exactly_one` not raising documented `WrongType` exception.
 
+### Changed
+
+- Breaking change: `Widget.anchor` now has different semantics. It should be applied to a container and anchors to the bottom of the scroll position. https://github.com/Textualize/textual/pull/5950
+
+### Added
+
+- Added `Markdown.append` https://github.com/Textualize/textual/pull/5950
+- Added `Widget.release_anchor` https://github.com/Textualize/textual/pull/5950
+
 ## [3.7.1] - 2025-07-09
 
 ### Fixed

examples/mother.py

@@ -74,6 +74,7 @@ def compose(self) -> ComposeResult:
     def on_mount(self) -> None:
         """You might want to change the model if you don't have access to it."""
         self.model = llm.get_model("gpt-4o")
+        self.query_one("#chat-view").anchor()
 
     @on(Input.Submitted)
     async def on_input(self, event: Input.Submitted) -> None:
@@ -82,8 +83,6 @@ async def on_input(self, event: Input.Submitted) -> None:
         event.input.clear()
         await chat_view.mount(Prompt(event.value))
         await chat_view.mount(response := Response())
-        response.anchor()
-
         self.send_prompt(event.value, response)
 
     @work(thread=True)

src/textual/_compositor.py

@@ -36,12 +36,12 @@
 from textual.geometry import NULL_SPACING, Offset, Region, Size, Spacing
 from textual.map_geometry import MapGeometry
 from textual.strip import Strip, StripRenderable
+from textual.widget import Widget
 
 if TYPE_CHECKING:
     from typing_extensions import TypeAlias
 
     from textual.screen import Screen
-    from textual.widget import Widget
 
 
 class ReflowResult(NamedTuple):
@@ -605,6 +605,18 @@ def add_widget(
                     # Get the region that will be updated
                     sub_clip = clip.intersection(child_region)
 
+                    if widget._anchored and not widget._anchor_released:
+                        scroll_y = widget.scroll_y
+                        new_scroll_y = (
+                            arrange_result.spatial_map.total_region.bottom
+                            - (
+                                widget.container_size.height
+                                - widget.scrollbar_size_horizontal
+                            )
+                        )
+                        widget.set_reactive(Widget.scroll_y, new_scroll_y)
+                        widget.watch_scroll_y(scroll_y, new_scroll_y)
+
                     if visible_only:
                         placements = arrange_result.get_visible_placements(
                             sub_clip - child_region.offset + widget.scroll_offset

src/textual/screen.py

@@ -1663,12 +1663,15 @@ def _watch__select_end(
         if end_region.y <= start_region.bottom or self._box_select:
             select_regions.append(Region.union(start_region, end_region))
         else:
-            container_region = Region.from_union(
-                [
-                    start_widget.select_container.content_region,
-                    end_widget.select_container.content_region,
-                ]
-            )
+            try:
+                container_region = Region.from_union(
+                    [
+                        start_widget.select_container.content_region,
+                        end_widget.select_container.content_region,
+                    ]
+                )
+            except NoMatches:
+                return
 
             start_region = Region.from_corners(
                 start_region.x,

src/textual/scrollbar.py

@@ -357,12 +357,14 @@ async def _on_mouse_up(self, event: events.MouseUp) -> None:
 
     def _on_mouse_capture(self, event: events.MouseCapture) -> None:
         if isinstance(self._parent, Widget):
-            self._parent._user_scroll_interrupt = True
+            self._parent.release_anchor()
         self.grabbed = event.mouse_position
         self.grabbed_position = self.position
 
     def _on_mouse_release(self, event: events.MouseRelease) -> None:
         self.grabbed = None
+        if self.vertical and isinstance(self.parent, Widget):
+            self.parent._check_anchor()
         event.stop()
 
     async def _on_mouse_move(self, event: events.MouseMove) -> None: