implement dim fix (#2326)

* implement dim fix

* docstrings

* foreground fix

* cached filters

* cache default

* fix for filter tests

* docstring

* optimization

* Update src/textual/filter.py

Co-authored-by: Rodrigo Girão Serrão <5621605+rodrigogiraoserrao@users.noreply.github.com>

* Update src/textual/constants.py

Co-authored-by: Rodrigo Girão Serrão <5621605+rodrigogiraoserrao@users.noreply.github.com>

---------

Co-authored-by: Rodrigo Girão Serrão <5621605+rodrigogiraoserrao@users.noreply.github.com>

src/textual/_styles_cache.py

@@ -2,7 +2,7 @@ from __future__ import annotations
 
 from functools import lru_cache
 from sys import intern
-from typing import TYPE_CHECKING, Callable, Iterable
+from typing import TYPE_CHECKING, Callable, Iterable, Sequence
 
 from rich.console import Console
 from rich.segment import Segment
@@ -139,7 +139,7 @@ class StylesCache:
             content_size=widget.content_region.size,
             padding=styles.padding,
             crop=crop,
-            filter=widget.app._filter,
+            filters=widget.app._filters,
         )
         if widget.auto_links:
             hover_style = widget.hover_style
@@ -170,7 +170,7 @@ class StylesCache:
         content_size: Size | None = None,
         padding: Spacing | None = None,
         crop: Region | None = None,
-        filter: LineFilter | None = None,
+        filters: Sequence[LineFilter] | None = None,
     ) -> list[Strip]:
         """Render a widget content plus CSS styles.
 
@@ -186,7 +186,7 @@ class StylesCache:
             content_size: Size of content or None to assume full size.
             padding: Override padding from Styles, or None to use styles.padding.
             crop: Region to crop to.
-            filter: Additional post-processing for the segments.
+            filters: Additional post-processing for the segments.
 
         Returns:
             Rendered lines.
@@ -225,8 +225,9 @@ class StylesCache:
                 self._cache[y] = strip
             else:
                 strip = self._cache[y]
-            if filter:
+            if filters:
-                strip = strip.apply_filter(filter)
+                for filter in filters:
+                    strip = strip.apply_filter(filter, background)
             add_strip(strip)
         self._dirty_lines.difference_update(crop.line_range)
 

src/textual/app.py

@@ -29,7 +29,6 @@ from contextlib import (
 from datetime import datetime
 from functools import partial
 from pathlib import Path, PurePath
-from queue import Queue
 from time import perf_counter
 from typing import (
     TYPE_CHECKING,
@@ -53,6 +52,7 @@ from weakref import WeakSet
 
 import rich
 import rich.repr
+from rich import terminal_theme
 from rich.console import Console, RenderableType
 from rich.protocol import is_renderable
 from rich.segment import Segment, Segments
@@ -81,7 +81,7 @@ from .driver import Driver
 from .drivers.headless_driver import HeadlessDriver
 from .features import FeatureFlag, parse_features
 from .file_monitor import FileMonitor
-from .filter import LineFilter, Monochrome
+from .filter import ANSIToTruecolor, DimFilter, LineFilter, Monochrome
 from .geometry import Offset, Region, Size
 from .keys import (
     REPLACED_KEYS,
@@ -260,11 +260,17 @@ class App(Generic[ReturnType], DOMNode):
         super().__init__()
         self.features: frozenset[FeatureFlag] = parse_features(os.getenv("TEXTUAL", ""))
 
-        self._filter: LineFilter | None = None
+        self._filters: list[LineFilter] = []
         environ = dict(os.environ)
         no_color = environ.pop("NO_COLOR", None)
         if no_color is not None:
-            self._filter = Monochrome()
+            self._filters.append(Monochrome())
+
+        for filter_name in constants.FILTERS.split(","):
+            filter = filter_name.lower().strip()
+            if filter == "dim":
+                self._filters.append(ANSIToTruecolor(terminal_theme.DIMMED_MONOKAI))
+                self._filters.append(DimFilter())
 
         self.console = Console(
             file=_NullFile(),

src/textual/constants.py

@@ -53,6 +53,9 @@ DEBUG: Final[bool] = get_environ_bool("TEXTUAL_DEBUG")
 
 DRIVER: Final[str | None] = get_environ("TEXTUAL_DRIVER", None)
 
+FILTERS: Final[str] = get_environ("TEXTUAL_FILTERS", "")
+"""A list of filters to apply to renderables."""
+
 LOG_FILE: Final[str | None] = get_environ("TEXTUAL_LOG", None)
 """A last resort log file that appends all logs, when devtools isn't working."""
 

src/textual/filter.py

@@ -6,6 +6,7 @@ from functools import lru_cache
 from rich.color import Color as RichColor
 from rich.segment import Segment
 from rich.style import Style
+from rich.terminal_theme import TerminalTheme
 
 from .color import Color
 
@@ -14,11 +15,12 @@ class LineFilter(ABC):
     """Base class for a line filter."""
 
     @abstractmethod
-    def apply(self, segments: list[Segment]) -> list[Segment]:
+    def apply(self, segments: list[Segment], background: Color) -> list[Segment]:
         """Transform a list of segments.
 
         Args:
             segments: A list of segments.
+            background: The background color.
 
         Returns:
             A new list of segments.
@@ -53,11 +55,12 @@ def monochrome_style(style: Style) -> Style:
 class Monochrome(LineFilter):
     """Convert all colors to monochrome."""
 
-    def apply(self, segments: list[Segment]) -> list[Segment]:
+    def apply(self, segments: list[Segment], background: Color) -> list[Segment]:
         """Transform a list of segments.
 
         Args:
             segments: A list of segments.
+            background: The background color.
 
         Returns:
             A new list of segments.
@@ -96,8 +99,11 @@ def dim_color(background: RichColor, color: RichColor, factor: float) -> RichCol
     )
 
 
+DEFAULT_COLOR = RichColor.default()
+
+
 @lru_cache(1024)
-def dim_style(style: Style, factor: float) -> Style:
+def dim_style(style: Style, background: Color, factor: float) -> Style:
     """Replace dim attribute with a dim color.
 
     Args:
@@ -109,9 +115,19 @@ def dim_style(style: Style, factor: float) -> Style:
     """
     return (
         style
-        + Style.from_color(dim_color(style.bgcolor, style.color, factor), None)
+        + Style.from_color(
-        + NO_DIM
+            dim_color(
-    )
+                (
+                    background.rich_color
+                    if style.bgcolor.is_default
+                    else (style.bgcolor or DEFAULT_COLOR)
+                ),
+                style.color or DEFAULT_COLOR,
+                factor,
+            ),
+            None,
+        )
+    ) + NO_DIM
 
 
 # Can be used as a workaround for https://github.com/xtermjs/xterm.js/issues/4161
@@ -126,11 +142,12 @@ class DimFilter(LineFilter):
         """
         self.dim_factor = dim_factor
 
-    def apply(self, segments: list[Segment]) -> list[Segment]:
+    def apply(self, segments: list[Segment], background: Color) -> list[Segment]:
         """Transform a list of segments.
 
         Args:
             segments: A list of segments.
+            background: The background color.
 
         Returns:
             A new list of segments.
@@ -143,7 +160,7 @@ class DimFilter(LineFilter):
             (
                 _Segment(
                     segment.text,
-                    _dim_style(segment.style, factor),
+                    _dim_style(segment.style, background, factor),
                     None,
                 )
                 if segment.style is not None and segment.style.dim
@@ -151,3 +168,60 @@ class DimFilter(LineFilter):
             )
             for segment in segments
         ]
+
+
+class ANSIToTruecolor(LineFilter):
+    """Convert ANSI colors to their truecolor equivalents."""
+
+    def __init__(self, terminal_theme: TerminalTheme):
+        """Initialise filter.
+
+        Args:
+            terminal_theme: A rich terminal theme.
+        """
+        self.terminal_theme = terminal_theme
+
+    @lru_cache(1024)
+    def truecolor_style(self, style: Style) -> Style:
+        """Replace system colors with truecolor equivalent.
+
+        Args:
+            style: Style to apply truecolor filter to.
+
+        Returns:
+            New style.
+        """
+        terminal_theme = self.terminal_theme
+        color = style.color
+        if color is not None and color.is_system_defined:
+            color = RichColor.from_rgb(
+                *color.get_truecolor(terminal_theme, foreground=True)
+            )
+        bgcolor = style.bgcolor
+        if bgcolor is not None and bgcolor.is_system_defined:
+            bgcolor = RichColor.from_rgb(
+                *bgcolor.get_truecolor(terminal_theme, foreground=False)
+            )
+        return style + Style.from_color(color, bgcolor)
+
+    def apply(self, segments: list[Segment], background: Color) -> list[Segment]:
+        """Transform a list of segments.
+
+        Args:
+            segments: A list of segments.
+            background: The background color.
+
+        Returns:
+            A new list of segments.
+        """
+        _Segment = Segment
+        truecolor_style = self.truecolor_style
+
+        return [
+            _Segment(
+                text,
+                None if style is None else truecolor_style(style),
+                None,
+            )
+            for text, style, _ in segments
+        ]

src/textual/strip.py

@@ -18,6 +18,7 @@ from rich.style import Style, StyleType
 
 from ._cache import FIFOCache
 from ._segment_tools import index_to_cell_position
+from .color import Color
 from .constants import DEBUG
 from .filter import LineFilter
 
@@ -67,6 +68,7 @@ class Strip:
         "_divide_cache",
         "_crop_cache",
         "_style_cache",
+        "_filter_cache",
         "_render_cache",
         "_link_ids",
     ]
@@ -79,6 +81,7 @@ class Strip:
         self._divide_cache: FIFOCache[tuple[int, ...], list[Strip]] = FIFOCache(4)
         self._crop_cache: FIFOCache[tuple[int, int], Strip] = FIFOCache(16)
         self._style_cache: FIFOCache[Style, Strip] = FIFOCache(16)
+        self._filter_cache: FIFOCache[tuple[LineFilter, Color], Strip] = FIFOCache(4)
         self._render_cache: str | None = None
         self._link_ids: set[str] | None = None
 
@@ -265,7 +268,7 @@ class Strip:
         )
         return line
 
-    def apply_filter(self, filter: LineFilter) -> Strip:
+    def apply_filter(self, filter: LineFilter, background: Color) -> Strip:
         """Apply a filter to all segments in the strip.
 
         Args:
@@ -274,7 +277,12 @@ class Strip:
         Returns:
             A new Strip.
         """
-        return Strip(filter.apply(self._segments), self._cell_length)
+        cached_strip = self._filter_cache.get((filter, background))
+        if cached_strip is None:
+            cached_strip = Strip(
+                filter.apply(self._segments, background), self._cell_length
+            )
+        return cached_strip
 
     def style_links(self, link_id: str, link_style: Style) -> Strip:
         """Apply a style to Segments with the given link_id.

tests/test_line_filter.py

@@ -1,6 +1,7 @@
 from rich.segment import Segment
 from rich.style import Style
 
+from textual.color import Color
 from textual.filter import DimFilter
 
 
@@ -11,7 +12,7 @@ def test_dim_apply():
 
     segments = [Segment("Hello, World!", Style.parse("dim #ffffff on #0000ff"))]
 
-    dimmed_segments = dim_filter.apply(segments)
+    dimmed_segments = dim_filter.apply(segments, Color(0, 0, 0))
 
     expected = [Segment("Hello, World!", Style.parse("not dim #7f7fff on #0000ff"))]
 

tests/test_strip.py

@@ -3,6 +3,7 @@ from rich.segment import Segment
 from rich.style import Style
 
 from textual._segment_tools import NoCellPositionForIndex
+from textual.color import Color
 from textual.filter import Monochrome
 from textual.strip import Strip
 
@@ -102,7 +103,7 @@ def test_apply_filter():
     expected = Strip([Segment("foo", Style.parse("#1b1b1b"))])
     print(repr(strip))
     print(repr(expected))
-    assert strip.apply_filter(Monochrome()) == expected
+    assert strip.apply_filter(Monochrome(), Color(0, 0, 0)) == expected
 
 
 def test_style_links():