Merge pull request #5311 from Textualize/scroll-optimization

optimize scroll

Author: willmcgugan

src/textual/scroll_view.py

@@ -82,10 +82,8 @@ def _size_updated(
             layout: Perform layout if required.
 
         Returns:
-            True if anything changed, or False if nothing changed.
+            True if a resize event should be sent, otherwise False.
         """
-        if self._size != size or self._container_size != container_size:
-            self.refresh()
         if (
             self._size != size
             or virtual_size != self.virtual_size
@@ -96,9 +94,8 @@ def _size_updated(
             virtual_size = self.virtual_size
             self._container_size = size - self.styles.gutter.totals
             self._scroll_update(virtual_size)
-            return True
-        else:
-            return False
+
+        return self._size != size or self._container_size != container_size
 
     def render(self) -> RenderableType:
         """Render the scrollable region (if `render_lines` is not implemented).

src/textual/widget.py

@@ -3695,8 +3695,9 @@ def _size_updated(
             layout: Perform layout if required.
 
         Returns:
-            True if anything changed, or False if nothing changed.
+            True if a resize event should be sent, otherwise False.
         """
+
         self._layout_cache.clear()
         if (
             self._size != size

src/textual/widgets/_option_list.py

@@ -362,19 +362,19 @@ def _add_lines(
                 self._lines.append(OptionLineSpan(-1, 0))
 
         self.virtual_size = Size(width, len(self._lines))
+        self.refresh(layout=self.styles.auto_dimensions)
+        self._scroll_update(self.virtual_size)
 
     def _populate(self) -> None:
         """Populate the lines data-structure."""
-        if self._lines is not None:
-            return
+
         self._lines = []
         self._spans = []
 
         self._add_lines(
             self._contents,
             self.scrollable_content_region.width - self._left_gutter_width(),
         )
-        self.refresh(layout=True)
 
     def get_content_width(self, container: Size, viewport: Size) -> int:
         """Get maximum width of options."""
@@ -824,8 +824,9 @@ def get_option_index(self, option_id: str) -> int:
             ) from None
 
     def render_line(self, y: int) -> Strip:
-        self._populate()
         assert self._lines is not None
+        if not self._lines:
+            self._populate()
 
         _scroll_x, scroll_y = self.scroll_offset
         line_number = scroll_y + y
@@ -879,9 +880,12 @@ def scroll_to_highlight(self, top: bool = False) -> None:
             top: Scroll highlight to top of the list.
         """
         highlighted = self.highlighted
-        if highlighted is None or self._spans is None:
+        if highlighted is None or not self.is_mounted:
             return
 
+        if not self._spans:
+            self._populate()
+
         try:
             y, height = self._spans[highlighted]
         except IndexError:
@@ -894,6 +898,7 @@ def scroll_to_highlight(self, top: bool = False) -> None:
             force=True,
             animate=False,
             top=top,
+            immediate=True,
         )
 
     def validate_highlighted(self, highlighted: int | None) -> int | None:
@@ -953,7 +958,6 @@ def _page(self, direction: Direction) -> None:
         # If we find ourselves in a position where we don't know where we're
         # going, we need a fallback location. Where we go will depend on the
         # direction.
-        self._populate()
         assert self._spans is not None
         assert self._lines is not None
 

src/textual/widgets/_select.py

@@ -66,7 +66,7 @@ def select(self, index: int | None) -> None:
             index: Index of new selection.
         """
         self.highlighted = index
-        self.scroll_to_highlight(top=True)
+        self.scroll_to_highlight()
 
     def action_dismiss(self) -> None:
         """Dismiss the overlay."""
@@ -520,7 +520,7 @@ def _watch_expanded(self, expanded: bool) -> None:
                 value = self.value
                 for index, (_prompt, prompt_value) in enumerate(self._options):
                     if value == prompt_value:
-                        overlay.select(index)
+                        self.call_after_refresh(overlay.select, index)
                         break
                 self.query_one(SelectCurrent).has_value = True