allow ansi color

CHANGELOG.md

@@ -14,13 +14,19 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Support for `"none"` value added to `dock`, `hatch` and `split` styles https://github.com/Textualize/textual/pull/4982
 - Support for `"none"` added to box and border style properties (e.g `widget.style.border = "none"`) https://github.com/Textualize/textual/pull/4982
 - Docstrings added to most style properties https://github.com/Textualize/textual/pull/4982
+- Added `ansi_color` switch to App to permit ANSI (themed) colors https://github.com/Textualize/textual/pull/5000
+- Added `:ansi` pseudo class https://github.com/Textualize/textual/pull/5000
+- Added `-ansi-scrollbar` style to widgets https://github.com/Textualize/textual/pull/5000
+- Added `App.INLINE_PADDING` to define the number of spaces above inline apps https://github.com/Textualize/textual/pull/5000
 
 ### Changed
 
 - Input validation for integers no longer accepts scientific notation like '1.5e2'; must be castable to int. https://github.com/Textualize/textual/pull/4784
 - Default `scrollbar-size-vertical` changed to `2` in inline styles to match Widget default CSS (unlikely to affect users) https://github.com/Textualize/textual/pull/4982
 - Removed border-right from `Toast` https://github.com/Textualize/textual/pull/4984
 - Some fixes in `RichLog` result in slightly different semantics, see docstrings for details https://github.com/Textualize/textual/pull/4978
+- Changed how scrollbars are rendered (will have no visual effect, but will break snapshot tests) https://github.com/Textualize/textual/pull/5000
+- Added `enabled` switch to filters (mostly used internally) https://github.com/Textualize/textual/pull/5000
 
 ### Fixed
 

docs/FAQ.md

@@ -68,7 +68,7 @@ For more information on ANSI colors in Textual, see [Why no Ansi Themes?](#why-d
 !!! tip
 
     See [*How To Center Things*](https://textual.textualize.io/how-to/center-things/) in the
-    Textual documentation for a more comprehensive answer to this question.
+    Textual documentation for a more comprensive answer to this question.
 
 To center a widget within a container use
 [`align`](https://textual.textualize.io/styles/align/). But remember that
@@ -270,7 +270,7 @@ work in different environments you can try them out with `textual keys`.
 <a name="why-doesn't-textual-look-good-on-macos"></a>
 ## Why doesn't Textual look good on macOS?
 
-You may find that the default macOS Terminal.app doesn't render Textual apps (and likely other TUIs) very well, particularly when it comes to box characters.
+You may find that the default macOS Terminal.app doesn't render Textual apps (and likely other TUIs) very well, particuarily when it comes to box characters.
 For instance, you may find it displays misaligned blocks and lines like this:
 
 <img width="1042" alt="Screenshot 2023-06-19 at 10 43 02" src="https://github.com/Textualize/textual/assets/554369/e61f3876-3dd1-4ac8-b380-22922c89c7d6">
@@ -319,6 +319,12 @@ Textual has a design system which guarantees apps will be readable on all platfo
 
 There is currently a light and dark version of the design system, but more are planned. It will also be possible for users to customize the source colors on a per-app or per-system basis. This means that in the future you will be able to modify the core colors to blend in with your chosen terminal theme.
 
+!!! Changed in 0.80.0
+
+  Textual added an `ansi_color` boolean to App. If you set this to `True`, then Textual will
+  not attempt to convert ansi colors. Note that you will lose transparency effects if you enable
+  this setting.
+
 ---
 
 <a name="why-doesn't-the-`datatable`-scroll-programmatically"></a>

docs/guide/app.md

@@ -51,6 +51,18 @@ To run an app in inline mode set the `inline` parameter to `True` when you call
 
     Inline mode is not currently supported on Windows.
 
+
+#### ANSI colors
+
+!!! tip "Added in version 0.80.0"
+
+Terminals support 16 theme-able *ANSI* colors, which you can personalize from your terminal settings.
+By default, Textual will replace these colors with its own color choices (see the [FAQ for details](../FAQ.md#why-doesnt-textual-support-ansi-themes)).
+
+You can disable this behavior by setting `ansi_color=True` in the [App constructor][textual.app.App].
+
+We recommend the default behavior for full-screen apps, but you may want to preserve ANSI colors in [inline](#run-inline) apps.
+
 ## Events
 
 Textual has an event system you can use to respond to key presses, mouse actions, and internal state changes. Event handlers are methods prefixed with `on_` followed by the name of the event.

questions/why-no-ansi-themes.question.md

@@ -15,3 +15,9 @@ This is an intentional design decision we took for for the following reasons:
 Textual has a design system which guarantees apps will be readable on all platforms and terminals, and produces better results than ANSI colors.
 
 There is currently a light and dark version of the design system, but more are planned. It will also be possible for users to customize the source colors on a per-app or per-system basis. This means that in the future you will be able to modify the core colors to blend in with your chosen terminal theme.
+
+!!! Changed in 0.80.0
+
+  Textual added an `ansi_color` boolean to App. If you set this to `True`, then Textual will
+  not attempt to convert ansi colors. Note that you will lose transparency effects if you enable
+  this setting.

src/textual/_border.py

@@ -237,6 +237,8 @@
 
 Borders: TypeAlias = Tuple[EdgeStyle, EdgeStyle, EdgeStyle, EdgeStyle]
 
+REVERSE_STYLE = Style(reverse=True)
+
 
 @lru_cache(maxsize=1024)
 def get_box(
@@ -249,9 +251,9 @@ def get_box(
 
     Args:
         name: Name of the box type.
-        inner_style: The inner style (widget background)
-        outer_style: The outer style (parent background)
-        style: Widget style
+        inner_style: The inner style (widget background).
+        outer_style: The outer style (parent background).
+        style: Widget style.
 
     Returns:
         A tuple of 3 Segment triplets.
@@ -271,11 +273,12 @@ def get_box(
 
     inner = inner_style + style
     outer = outer_style + style
+
     styles = (
         inner,
         outer,
-        Style.from_color(outer.bgcolor, inner.color),
-        Style.from_color(inner.bgcolor, outer.color),
+        Style.from_color(inner.color, outer.bgcolor) + REVERSE_STYLE,
+        Style.from_color(outer.color, inner.bgcolor) + REVERSE_STYLE,
     )
 
     return (
@@ -363,9 +366,9 @@ def render_border_label(
     elif label_style_location == 1:
         base_style = outer
     elif label_style_location == 2:
-        base_style = Style.from_color(outer.bgcolor, inner.color)
+        base_style = Style.from_color(inner.color, outer.bgcolor) + REVERSE_STYLE
     elif label_style_location == 3:
-        base_style = Style.from_color(inner.bgcolor, outer.color)
+        base_style = Style.from_color(outer.color, inner.bgcolor) + REVERSE_STYLE
     else:
         assert False
 

src/textual/_color_constants.py

@@ -1,5 +1,25 @@
 from __future__ import annotations
 
+ANSI_COLORS = [
+    "black",
+    "red",
+    "green",
+    "yellow",
+    "blue",
+    "magenta",
+    "cyan",
+    "white",
+    "bright_black",
+    "bright_red",
+    "bright_green",
+    "bright_yellow",
+    "bright_blue",
+    "bright_magenta",
+    "bright_cyan",
+    "bright_white",
+]
+"""The names of ANSI colors (prefixed with ansi_ in CSS)."""
+
 COLOR_NAME_TO_RGB: dict[str, tuple[int, int, int] | tuple[int, int, int, int]] = {
     # Let's start with a specific pseudo-color::
     "transparent": (0, 0, 0, 0),

src/textual/_styles_cache.py

@@ -213,6 +213,9 @@ 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(
@@ -233,9 +236,8 @@ def render(
             else:
                 strip = self._cache[y]
 
-            if filters:
-                for filter in filters:
-                    strip = strip.apply_filter(filter, background)
+            for filter in apply_filters:
+                strip = strip.apply_filter(filter, background)
 
             if DEBUG:
                 if any([not (segment.control or segment.text) for segment in strip]):

src/textual/app.py

@@ -172,6 +172,19 @@
         accent="#0178D4",
         dark=False,
     ),
+    "ansi": ColorSystem(
+        "ansi_blue",
+        secondary="ansi_cyan",
+        warning="ansi_yellow",
+        error="ansi_red",
+        success="ansi_green",
+        accent="ansi_bright_blue",
+        foreground="ansi_default",
+        background="ansi_default",
+        surface="ansi_default",
+        panel="ansi_default",
+        boost="ansi_default",
+    ),
 }
 
 ComposeResult = Iterable[Widget]
@@ -317,6 +330,20 @@ class App(Generic[ReturnType], DOMNode):
         background: $background;
         color: $text;
 
+        &:ansi {
+            background: ansi_default;
+            color: ansi_default;
+
+            .-ansi-scrollbar {
+                scrollbar-background: ansi_default;
+                scrollbar-background-hover: ansi_default;
+                scrollbar-background-active: ansi_default;
+                scrollbar-color: ansi_blue;
+                scrollbar-color-active: ansi_bright_blue;
+                scrollbar-color-hover: ansi_bright_blue;               
+            }
+        }
+
         /* When a widget is maximized */
         Screen.-maximized-view {                    
             layout: vertical !important;
@@ -434,6 +461,9 @@ class MyApp(App[None]):
     This is the default value, used if the active screen's `ESCAPE_TO_MINIMIZE` is not changed from `None`.
     """
 
+    INLINE_PADDING: ClassVar[int] = 1
+    """Number of blank lines above an inline app."""
+
     title: Reactive[str] = Reactive("", compute=False)
     """The title of the app, displayed in the header."""
     sub_title: Reactive[str] = Reactive("", compute=False)
@@ -462,11 +492,15 @@ class MyApp(App[None]):
     ansi_theme_light = Reactive(ALABASTER, init=False)
     """Maps ANSI colors to hex colors using a Rich TerminalTheme object while in light mode."""
 
+    ansi_color = Reactive(False)
+    """Allow ANSI colors in UI?"""
+
     def __init__(
         self,
         driver_class: Type[Driver] | None = None,
         css_path: CSSPathType | None = None,
         watch_css: bool = False,
+        ansi_color: bool = False,
     ):
         """Create an instance of an app.
 
@@ -478,6 +512,7 @@ def __init__(
                 will be loaded in order.
             watch_css: Reload CSS if the files changed. This is set automatically if
                 you are using `textual run` with the `dev` switch.
+            ansi_color: Allow ANSI colors if `True`, or convert ANSI colors to to RGB if `False`.
 
         Raises:
             CssPathError: When the supplied CSS path(s) are an unexpected type.
@@ -487,8 +522,10 @@ def __init__(
         self.features: frozenset[FeatureFlag] = parse_features(os.getenv("TEXTUAL", ""))
 
         ansi_theme = self.ansi_theme_dark if self.dark else self.ansi_theme_light
-        self._filters: list[LineFilter] = [ANSIToTruecolor(ansi_theme)]
-
+        self.set_reactive(App.ansi_color, ansi_color)
+        self._filters: list[LineFilter] = [
+            ANSIToTruecolor(ansi_theme, enabled=not ansi_color)
+        ]
         environ = dict(os.environ)
         no_color = environ.pop("NO_COLOR", None)
         if no_color is not None:
@@ -840,6 +877,14 @@ def get_pseudo_classes(self) -> Iterable[str]:
         yield "dark" if self.dark else "light"
         if self.is_inline:
             yield "inline"
+        if self.ansi_color:
+            yield "ansi"
+
+    def _watch_ansi_color(self, ansi_color: bool) -> None:
+        """Enable or disable the truecolor filter when the reactive changes"""
+        for filter in self._filters:
+            if isinstance(filter, ANSIToTruecolor):
+                filter.enabled = not ansi_color
 
     def animate(
         self,
@@ -1016,18 +1061,19 @@ def get_system_commands(self, screen: Screen) -> Iterable[SystemCommand]:
         Yields:
             [SystemCommand][textual.app.SystemCommand] instances.
         """
-        if self.dark:
-            yield SystemCommand(
-                "Light mode",
-                "Switch to a light background",
-                self.action_toggle_dark,
-            )
-        else:
-            yield SystemCommand(
-                "Dark mode",
-                "Switch to a dark background",
-                self.action_toggle_dark,
-            )
+        if not self.ansi_color:
+            if self.dark:
+                yield SystemCommand(
+                    "Light mode",
+                    "Switch to a light background",
+                    self.action_toggle_dark,
+                )
+            else:
+                yield SystemCommand(
+                    "Dark mode",
+                    "Switch to a dark background",
+                    self.action_toggle_dark,
+                )
 
         yield SystemCommand(
             "Quit the application",
@@ -1093,7 +1139,13 @@ def get_css_variables(self) -> dict[str, str]:
         Returns:
             A mapping of variable name to value.
         """
-        variables = self.design["dark" if self.dark else "light"].generate()
+
+        if self.dark:
+            design = self.design["dark"]
+        else:
+            design = self.design["light"]
+
+        variables = design.generate()
         return variables
 
     def watch_dark(self, dark: bool) -> None:
@@ -1135,7 +1187,7 @@ def _refresh_truecolor_filter(self, theme: TerminalTheme) -> None:
         filters = self._filters
         for index, filter in enumerate(filters):
             if isinstance(filter, ANSIToTruecolor):
-                filters[index] = ANSIToTruecolor(theme)
+                filters[index] = ANSIToTruecolor(theme, enabled=not self.ansi_color)
                 return
 
     def get_driver_class(self) -> Type[Driver]: