optimizations in styles cache

CHANGELOG.md

@@ -20,11 +20,13 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Added `OptionList.set_options` https://github.com/Textualize/textual/pull/6048
 - Added `TextArea.suggestion` https://github.com/Textualize/textual/pull/6048
 - Added `TextArea.placeholder` https://github.com/Textualize/textual/pull/6048
+- Added `Widget.get_line_filters` and `App.get_line_filters` https://github.com/Textualize/textual/pull/6057
 
 ### Changed
 
 - Breaking change: The `renderable` property on the `Static` widget has been changed to `content`. https://github.com/Textualize/textual/pull/6041
 - Breaking change: Renamed `Label` constructor argument `renderable` to `content` for consistency https://github.com/Textualize/textual/pull/6045
+- Breaking change: Optimization to line API to avoid applying background styles to widget content. In practice this means that you can no longer rely on blank Segments automatically getting the background color.
 
 # [5.3.0] - 2025-08-07
 

src/textual/_segment_tools.py

@@ -5,6 +5,7 @@
 from __future__ import annotations
 
 import re
+from functools import lru_cache
 from typing import Iterable
 
 from rich.segment import Segment
@@ -15,6 +16,20 @@
 from textual.geometry import Size
 
 
+@lru_cache(1024 * 8)
+def make_blank(width, style: Style) -> Segment:
+    """Make a blank segment.
+
+    Args:
+        width: Width of blank.
+        style: Style of blank.
+
+    Returns:
+        A single segment
+    """
+    return Segment(" " * width, style)
+
+
 class NoCellPositionForIndex(Exception):
     pass
 
@@ -162,19 +177,19 @@ def line_pad(
     """
     if pad_left and pad_right:
         return [
-            Segment(" " * pad_left, style),
+            make_blank(pad_left, style),
             *segments,
-            Segment(" " * pad_right, style),
+            make_blank(pad_right, style),
         ]
     elif pad_left:
         return [
-            Segment(" " * pad_left, style),
+            make_blank(pad_left, style),
             *segments,
         ]
     elif pad_right:
         return [
             *segments,
-            Segment(" " * pad_right, style),
+            make_blank(pad_right, style),
         ]
     return list(segments)
 
@@ -215,7 +230,7 @@ def blank_lines(count: int) -> list[list[Segment]]:
         Returns:
             A list of blank lines.
         """
-        return [[Segment(" " * width, style)]] * count
+        return [[make_blank(width, style)]] * count
 
     top_blank_lines = bottom_blank_lines = 0
     vertical_excess_space = max(0, height - shape_height)

src/textual/_styles_cache.py

@@ -1,7 +1,6 @@
 from __future__ import annotations
 
 from functools import lru_cache
-from sys import intern
 from typing import TYPE_CHECKING, Callable, Iterable, Sequence
 
 import rich.repr
@@ -14,7 +13,7 @@
 from textual._border import get_box, render_border_label, render_row
 from textual._context import active_app
 from textual._opacity import _apply_opacity
-from textual._segment_tools import apply_hatch, line_pad, line_trim
+from textual._segment_tools import apply_hatch, line_pad, line_trim, make_blank
 from textual.color import TRANSPARENT, Color
 from textual.constants import DEBUG
 from textual.content import Content
@@ -34,20 +33,6 @@
 RenderLineCallback: TypeAlias = Callable[[int], Strip]
 
 
-@lru_cache(1024 * 8)
-def make_blank(width, style: RichStyle) -> Segment:
-    """Make a blank segment.
-
-    Args:
-        width: Width of blank.
-        style: Style of blank.
-
-    Returns:
-        A single segment
-    """
-    return Segment(intern(" " * width), style)
-
-
 @rich.repr.auto(angular=True)
 class StylesCache:
     """Responsible for rendering CSS Styles and keeping a cache of rendered lines.
@@ -105,6 +90,7 @@ def is_dirty(self, y: int) -> bool:
 
     def clear(self) -> None:
         """Clear the styles cache (will cause the content to re-render)."""
+
         self._cache.clear()
         self._dirty_lines.clear()
 
@@ -122,14 +108,15 @@ def render_widget(self, widget: Widget, crop: Region) -> list[Strip]:
         border_title = widget._border_title
         border_subtitle = widget._border_subtitle
 
-        base_background, background = widget._opacity_background_colors
+        base_background, background = widget.background_colors
         styles = widget.styles
         strips = self.render(
             styles,
             widget.region.size,
             base_background,
             background,
             widget.render_line,
+            widget.get_line_filters(),
             (
                 None
                 if border_title is None
@@ -149,7 +136,6 @@ def render_widget(self, widget: Widget, crop: Region) -> list[Strip]:
             content_size=widget.content_region.size,
             padding=styles.padding,
             crop=crop,
-            filters=widget.app._filters,
             opacity=widget.opacity,
             ansi_theme=widget.app.ansi_theme,
         )
@@ -177,12 +163,12 @@ def render(
         base_background: Color,
         background: Color,
         render_content_line: RenderLineCallback,
+        filters: Sequence[LineFilter],
         border_title: tuple[Content, Color, Color, Style] | None,
         border_subtitle: tuple[Content, Color, Color, Style] | None,
         content_size: Size | None = None,
         padding: Spacing | None = None,
         crop: Region | None = None,
-        filters: Sequence[LineFilter] | None = None,
         opacity: float = 1.0,
         ansi_theme: TerminalTheme = DEFAULT_TERMINAL_THEME,
     ) -> list[Strip]:
@@ -223,9 +209,7 @@ def render(
 
         is_dirty = self._dirty_lines.__contains__
         render_line = self.render_line
-        apply_filters = (
-            [] if filters is None else [filter for filter in filters if filter.enabled]
-        )
+
         for y in crop.line_range:
             if is_dirty(y) or y not in self._cache:
                 strip = render_line(
@@ -246,7 +230,7 @@ def render(
             else:
                 strip = self._cache[y]
 
-            for filter in apply_filters:
+            for filter in filters:
                 strip = strip.apply_filter(filter, background)
 
             if DEBUG:
@@ -263,6 +247,16 @@ def render(
 
         return strips
 
+    @lru_cache(1024)
+    def get_inner_outer(
+        cls, base_background: Color, background: Color
+    ) -> tuple[Style, Style]:
+        """Get inner and outer background colors."""
+        return (
+            Style(background=base_background + background),
+            Style(background=base_background),
+        )
+
     def render_line(
         self,
         styles: StylesBase,
@@ -319,9 +313,7 @@ def render_line(
         ) = styles.outline
 
         from_color = RichStyle.from_color
-
-        inner = Style(background=(base_background + background))
-        outer = Style(background=base_background)
+        inner, outer = self.get_inner_outer(base_background, background)
 
         def line_post(segments: Iterable[Segment]) -> Iterable[Segment]:
             """Apply effects to segments inside the border."""
@@ -343,7 +335,6 @@ def post(segments: Iterable[Segment]) -> Iterable[Segment]:
             Returns:
                 New list of segments
             """
-
             try:
                 app = active_app.get()
                 ansi_theme = app.ansi_theme
@@ -361,7 +352,6 @@ def post(segments: Iterable[Segment]) -> Iterable[Segment]:
         line: Iterable[Segment]
         # Draw top or bottom borders (A)
         if (border_top and y == 0) or (border_bottom and y == height - 1):
-
             is_top = y == 0
             border_color = base_background + (
                 border_top_color if is_top else border_bottom_color
@@ -427,7 +417,7 @@ def post(segments: Iterable[Segment]) -> Iterable[Segment]:
         elif (pad_top and y < gutter.top) or (
             pad_bottom and y >= height - gutter.bottom
         ):
-            background_rich_style = from_color(bgcolor=background.rich_color)
+            background_rich_style = inner.rich_style
             left_style = Style(
                 foreground=base_background + border_left_color.multiply_alpha(opacity)
             )
@@ -450,15 +440,12 @@ def post(segments: Iterable[Segment]) -> Iterable[Segment]:
             content_y = y - gutter.top
             if content_y < content_height:
                 line = render_content_line(y - gutter.top)
-                line = line.adjust_cell_length(content_width)
+                line = line.adjust_cell_length(content_width, inner.rich_style)
             else:
-                line = [make_blank(content_width, inner.rich_style)]
-            if inner:
-                line = Segment.apply_style(line, inner.rich_style)
-            if styles.text_opacity != 1.0:
-                line = TextOpacity.process_segments(
-                    line, styles.text_opacity, ansi_theme
-                )
+                line = Strip.blank(content_width, inner.rich_style)
+
+            if (text_opacity := styles.text_opacity) != 1.0:
+                line = TextOpacity.process_segments(line, text_opacity, ansi_theme)
             line = line_post(line_pad(line, pad_left, pad_right, inner.rich_style))
 
             if border_left or border_right:

src/textual/app.py

@@ -842,6 +842,14 @@ def __init__(
                     )
                 )
 
+    def get_line_filters(self) -> Sequence[LineFilter]:
+        """Get currently enabled line filters.
+
+        Returns:
+            A list of [LineFilter][textual.filters.LineFilter] instances.
+        """
+        return [filter for filter in self._filters if filter.enabled]
+
     @property
     def _is_devtools_connected(self) -> bool:
         """Is the app connected to the devtools?"""
@@ -3160,7 +3168,6 @@ async def _process_messages(
         terminal_size: tuple[int, int] | None = None,
         message_hook: Callable[[Message], None] | None = None,
     ) -> None:
-
         self._thread_init()
 
         async def app_prelude() -> bool:

src/textual/dom.py

@@ -1146,26 +1146,12 @@ def _get_subtitle_style_information(
 
     @property
     def background_colors(self) -> tuple[Color, Color]:
-        """The background color and the color of the parent's background.
-
-        Returns:
-            `(<background color>, <color>)`
-        """
-        base_background = background = BLACK
-        for node in reversed(self.ancestors_with_self):
-            styles = node.styles
-            base_background = background
-            background += styles.background.tint(styles.background_tint)
-        return (base_background, background)
-
-    @property
-    def _opacity_background_colors(self) -> tuple[Color, Color]:
         """Background colors adjusted for opacity.
 
         Returns:
             `(<background color>, <color>)`
         """
-        base_background = background = BLACK
+        base_background = background = Color(0, 0, 0, 0)
         opacity = 1.0
         for node in reversed(self.ancestors_with_self):
             styles = node.styles

src/textual/filter.py

@@ -240,22 +240,26 @@ def truecolor_style(self, style: Style, background: RichColor) -> Style:
             New style.
         """
         terminal_theme = self._terminal_theme
-        color = style.color
-        if color is not None and color.triplet is None:
-            color = RichColor.from_rgb(
-                *color.get_truecolor(terminal_theme, foreground=True)
-            )
-        bgcolor = style.bgcolor
-        if bgcolor is not None and bgcolor.triplet is None:
-            bgcolor = RichColor.from_rgb(
-                *bgcolor.get_truecolor(terminal_theme, foreground=False)
+
+        changed = False
+        if (color := style.color) is not None:
+            if color.triplet is None:
+                color = RichColor.from_triplet(
+                    color.get_truecolor(terminal_theme, foreground=True)
+                )
+                changed = True
+            if style.dim:
+                color = dim_color(background, color)
+                style += NO_DIM
+                changed = True
+
+        if (bgcolor := style.bgcolor) is not None and bgcolor.triplet is None:
+            bgcolor = RichColor.from_triplet(
+                bgcolor.get_truecolor(terminal_theme, foreground=False)
             )
-        # Convert dim style to RGB
-        if style.dim and color is not None:
-            color = dim_color(background, color)
-            style += NO_DIM
+            changed = True
 
-        return style + Style.from_color(color, bgcolor)
+        return style + Style.from_color(color, bgcolor) if changed else style
 
     def apply(self, segments: list[Segment], background: Color) -> list[Segment]:
         """Transform a list of segments.
@@ -269,9 +273,7 @@ def apply(self, segments: list[Segment], background: Color) -> list[Segment]:
         """
         _Segment = Segment
         truecolor_style = self.truecolor_style
-
         background_rich_color = background.rich_color
-
         return [
             _Segment(
                 text,

src/textual/renderables/text_opacity.py

@@ -79,6 +79,8 @@ def process_segments(
             ):
                 invisible_style = _from_color(bgcolor=style.bgcolor)
                 yield _Segment(cell_len(text) * " ", invisible_style)
+        elif opacity == 1:
+            yield from segments
         else:
             filter = ANSIToTruecolor(ansi_theme)
             for segment in filter.apply(list(segments), TRANSPARENT):

src/textual/scroll_view.py

@@ -36,13 +36,13 @@ def watch_scroll_x(self, old_value: float, new_value: float) -> None:
         if self.show_horizontal_scrollbar:
             self.horizontal_scrollbar.position = new_value
         if round(old_value) != round(new_value):
-            self.refresh()
+            self.refresh(self.size.region)
 
     def watch_scroll_y(self, old_value: float, new_value: float) -> None:
         if self.show_vertical_scrollbar:
             self.vertical_scrollbar.position = new_value
         if round(old_value) != round(new_value):
-            self.refresh()
+            self.refresh(self.size.region)
 
     def on_mount(self):
         self._refresh_scrollbars()

src/textual/scrollbar.py

@@ -287,7 +287,7 @@ def render(self) -> RenderableType:
             background = styles.scrollbar_background
             color = styles.scrollbar_color
         if background.a < 1:
-            base_background, _ = self.parent._opacity_background_colors
+            base_background, _ = self.parent.background_colors
             background = base_background + background
         color = background + color
         scrollbar_style = Style.from_color(color.rich_color, background.rich_color)