Add support for env variable TEXTUAL_ANIMATIONS

CHANGELOG.md

@@ -5,6 +5,13 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+## Unreleased
+
+### Added
+
+- Added support for environment variable `TEXTUAL_ANIMATIONS` to control what animations Textual displays https://github.com/Textualize/textual/pull/4062
+- Add attribute `App.animation_level` to control whether animations on that app run or not https://github.com/Textualize/textual/pull/4062
+
 ## [0.51.0] - 2024-02-15
 
 ### Added
@@ -121,6 +128,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Added `App.suspend` https://github.com/Textualize/textual/pull/4064
 - Added `App.action_suspend_process` https://github.com/Textualize/textual/pull/4064
 
+
 ### Fixed
 
 - Parameter `animate` from `DataTable.move_cursor` was being ignored https://github.com/Textualize/textual/issues/3840

docs/api/constants.md

@@ -0,0 +1 @@
+::: textuals.constants

mkdocs-nav.yml

@@ -178,6 +178,7 @@ nav:
       - "api/cache.md"
       - "api/color.md"
       - "api/command.md"
+      - "api/constants.md"
       - "api/containers.md"
       - "api/content_switcher.md"
       - "api/coordinate.md"

src/textual/_animator.py

@@ -11,7 +11,7 @@
 from . import _time
 from ._callback import invoke
 from ._easing import DEFAULT_EASING, EASING
-from ._types import CallbackType
+from ._types import AnimationLevel, CallbackType
 from .timer import Timer
 
 if TYPE_CHECKING:
@@ -53,7 +53,11 @@ class Animation(ABC):
     """Callback to run after animation completes"""
 
     @abstractmethod
-    def __call__(self, time: float) -> bool:  # pragma: no cover
+    def __call__(
+        self,
+        time: float,
+        app_animation_level: AnimationLevel = "full",
+    ) -> bool:  # pragma: no cover
         """Call the animation, return a boolean indicating whether animation is in-progress or complete.
 
         Args:
@@ -93,9 +97,18 @@ class SimpleAnimation(Animation):
     final_value: object
     easing: EasingFunction
     on_complete: CallbackType | None = None
+    level: AnimationLevel = "full"
+    """Minimum level required for the animation to take place (inclusive)."""
 
-    def __call__(self, time: float) -> bool:
-        if self.duration == 0:
+    def __call__(
+        self, time: float, app_animation_level: AnimationLevel = "full"
+    ) -> bool:
+        if (
+            self.duration == 0
+            or app_animation_level == "none"
+            or app_animation_level == "basic"
+            and self.level == "full"
+        ):
             setattr(self.obj, self.attribute, self.final_value)
             return True
 
@@ -170,6 +183,7 @@ def __call__(
         delay: float = 0.0,
         easing: EasingFunction | str = DEFAULT_EASING,
         on_complete: CallbackType | None = None,
+        level: AnimationLevel = "full",
     ) -> None:
         """Animate an attribute.
 
@@ -182,6 +196,7 @@ def __call__(
             delay: A delay (in seconds) before the animation starts.
             easing: An easing method.
             on_complete: A callable to invoke when the animation is finished.
+            level: Minimum level required for the animation to take place (inclusive).
         """
         start_value = getattr(self._obj, attribute)
         if isinstance(value, str) and hasattr(start_value, "parse"):
@@ -200,6 +215,7 @@ def __call__(
             delay=delay,
             easing=easing_function,
             on_complete=on_complete,
+            level=level,
         )
 
 
@@ -284,6 +300,7 @@ def animate(
         easing: EasingFunction | str = DEFAULT_EASING,
         delay: float = 0.0,
         on_complete: CallbackType | None = None,
+        level: AnimationLevel = "full",
     ) -> None:
         """Animate an attribute to a new value.
 
@@ -297,6 +314,7 @@ def animate(
             easing: An easing function.
             delay: Number of seconds to delay the start of the animation by.
             on_complete: Callback to run after the animation completes.
+            level: Minimum level required for the animation to take place (inclusive).
         """
         animate_callback = partial(
             self._animate,
@@ -308,6 +326,7 @@ def animate(
             speed=speed,
             easing=easing,
             on_complete=on_complete,
+            level=level,
         )
         if delay:
             self._complete_event.clear()
@@ -328,7 +347,8 @@ def _animate(
         speed: float | None = None,
         easing: EasingFunction | str = DEFAULT_EASING,
         on_complete: CallbackType | None = None,
-    ):
+        level: AnimationLevel = "full",
+    ) -> None:
         """Animate an attribute to a new value.
 
         Args:
@@ -340,6 +360,7 @@ def _animate(
             speed: The speed of the animation.
             easing: An easing function.
             on_complete: Callback to run after the animation completes.
+            level: Minimum level required for the animation to take place (inclusive).
         """
         if not hasattr(obj, attribute):
             raise AttributeError(
@@ -373,6 +394,7 @@ def _animate(
                 speed=speed,
                 easing=easing_function,
                 on_complete=on_complete,
+                level=level,
             )
 
         if animation is None:
@@ -414,6 +436,7 @@ def _animate(
                     if on_complete is not None
                     else None
                 ),
+                level=level,
             )
         assert animation is not None, "animation expected to be non-None"
 
@@ -521,11 +544,12 @@ def __call__(self) -> None:
             if not self._scheduled:
                 self._complete_event.set()
         else:
+            app_animation_level = self.app.animation_level
             animation_time = self._get_time()
             animation_keys = list(self._animations.keys())
             for animation_key in animation_keys:
                 animation = self._animations[animation_key]
-                animation_complete = animation(animation_time)
+                animation_complete = animation(animation_time, app_animation_level)
                 if animation_complete:
                     del self._animations[animation_key]
                     if animation.on_complete is not None:

src/textual/_context.py

@@ -14,12 +14,14 @@ class NoActiveAppError(RuntimeError):
     """Runtime error raised if we try to retrieve the active app when there is none."""
 
 
-active_app: ContextVar["App"] = ContextVar("active_app")
+active_app: ContextVar["App[object]"] = ContextVar("active_app")
 active_message_pump: ContextVar["MessagePump"] = ContextVar("active_message_pump")
 prevent_message_types_stack: ContextVar[list[set[type[Message]]]] = ContextVar(
     "prevent_message_types_stack"
 )
-visible_screen_stack: ContextVar[list[Screen]] = ContextVar("visible_screen_stack")
+visible_screen_stack: ContextVar[list[Screen[object]]] = ContextVar(
+    "visible_screen_stack"
+)
 """A stack of visible screens (with background alpha < 1), used in the screen render process."""
 message_hook: ContextVar[Callable[[Message], None]] = ContextVar("message_hook")
 """A callable that accepts a message. Used by App.run_test."""

src/textual/_types.py

@@ -1,4 +1,4 @@
-from typing import TYPE_CHECKING, Any, Awaitable, Callable, List, Union
+from typing import TYPE_CHECKING, Any, Awaitable, Callable, List, Literal, Union
 
 from typing_extensions import Protocol
 
@@ -52,3 +52,6 @@ class UnusedParameter:
     WatchCallbackNoArgsType,
 ]
 """Type used for callbacks passed to the `watch` method of widgets."""
+
+AnimationLevel = Literal["none", "basic", "full"]
+"""The levels that the [`TEXTUAL_ANIMATIONS`][textual.constants.TEXTUAL_ANIMATIONS] env var can be set to."""

src/textual/app.py

@@ -78,6 +78,7 @@
 from ._context import message_hook as message_hook_context_var
 from ._event_broker import NoHandler, extract_handler_actions
 from ._path import CSSPathType, _css_path_type_as_list, _make_path_object_relative
+from ._types import AnimationLevel
 from ._wait import wait_for_idle
 from ._worker_manager import WorkerManager
 from .actions import ActionParseResult, SkipAction
@@ -614,6 +615,12 @@ def __init__(
         self.set_class(self.dark, "-dark-mode")
         self.set_class(not self.dark, "-light-mode")
 
+        self.animation_level: AnimationLevel = constants.TEXTUAL_ANIMATIONS
+        """Determines what type of animations the app will display.
+
+        See [`textual.constants.TEXTUAL_ANIMATIONS`][textual.constants.TEXTUAL_ANIMATIONS].
+        """
+
     def validate_title(self, title: Any) -> str:
         """Make sure the title is set to a string."""
         return str(title)
@@ -709,6 +716,7 @@ def animate(
         delay: float = 0.0,
         easing: EasingFunction | str = DEFAULT_EASING,
         on_complete: CallbackType | None = None,
+        level: AnimationLevel = "full",
     ) -> None:
         """Animate an attribute.
 
@@ -723,6 +731,7 @@ def animate(
             delay: A delay (in seconds) before the animation starts.
             easing: An easing method.
             on_complete: A callable to invoke when the animation is finished.
+            level: Minimum level required for the animation to take place (inclusive).
         """
         self._animate(
             attribute,
@@ -733,6 +742,7 @@ def animate(
             delay=delay,
             easing=easing,
             on_complete=on_complete,
+            level=level,
         )
 
     async def stop_animation(self, attribute: str, complete: bool = True) -> None:

src/textual/constants.py

@@ -5,13 +5,16 @@
 from __future__ import annotations
 
 import os
+from typing import get_args
 
-from typing_extensions import Final
+from typing_extensions import Final, TypeGuard
+
+from ._types import AnimationLevel
 
 get_environ = os.environ.get
 
 
-def get_environ_bool(name: str) -> bool:
+def _get_environ_bool(name: str) -> bool:
     """Check an environment variable switch.
 
     Args:
@@ -24,7 +27,7 @@ def get_environ_bool(name: str) -> bool:
     return has_environ
 
 
-def get_environ_int(name: str, default: int) -> int:
+def _get_environ_int(name: str, default: int) -> int:
     """Retrieves an integer environment variable.
 
     Args:
@@ -44,7 +47,34 @@ def get_environ_int(name: str, default: int) -> int:
         return default
 
 
-DEBUG: Final[bool] = get_environ_bool("TEXTUAL_DEBUG")
+def _is_valid_animation_level(value: str) -> TypeGuard[AnimationLevel]:
+    """Checks if a string is a valid animation level.
+
+    Args:
+        value: The string to check.
+
+    Returns:
+        Whether it's a valid level or not.
+    """
+    return value in get_args(AnimationLevel)
+
+
+def _get_textual_animations() -> AnimationLevel:
+    """Get the value of the environment variable that controls textual animations.
+
+    The variable can be in any of the values defined by [`AnimationLevel`][textual.constants.AnimationLevel].
+
+    Returns:
+        The value that the variable was set to. If the environment variable is set to an
+            invalid value, we default to showing all animations.
+    """
+    value: str = get_environ("TEXTUAL_ANIMATIONS", "FULL").lower()
+    if _is_valid_animation_level(value):
+        return value
+    return "full"
+
+
+DEBUG: Final[bool] = _get_environ_bool("TEXTUAL_DEBUG")
 """Enable debug mode."""
 
 DRIVER: Final[str | None] = get_environ("TEXTUAL_DRIVER", None)
@@ -59,20 +89,23 @@ def get_environ_int(name: str, default: int) -> int:
 DEVTOOLS_HOST: Final[str] = get_environ("TEXTUAL_DEVTOOLS_HOST", "127.0.0.1")
 """The host where textual console is running."""
 
-DEVTOOLS_PORT: Final[int] = get_environ_int("TEXTUAL_DEVTOOLS_PORT", 8081)
+DEVTOOLS_PORT: Final[int] = _get_environ_int("TEXTUAL_DEVTOOLS_PORT", 8081)
 """Constant with the port that the devtools will connect to."""
 
-SCREENSHOT_DELAY: Final[int] = get_environ_int("TEXTUAL_SCREENSHOT", -1)
+SCREENSHOT_DELAY: Final[int] = _get_environ_int("TEXTUAL_SCREENSHOT", -1)
 """Seconds delay before taking screenshot."""
 
 PRESS: Final[str] = get_environ("TEXTUAL_PRESS", "")
 """Keys to automatically press."""
 
-SHOW_RETURN: Final[bool] = get_environ_bool("TEXTUAL_SHOW_RETURN")
+SHOW_RETURN: Final[bool] = _get_environ_bool("TEXTUAL_SHOW_RETURN")
 """Write the return value on exit."""
 
-MAX_FPS: Final[int] = get_environ_int("TEXTUAL_FPS", 60)
+MAX_FPS: Final[int] = _get_environ_int("TEXTUAL_FPS", 60)
 """Maximum frames per second for updates."""
 
 COLOR_SYSTEM: Final[str | None] = get_environ("TEXTUAL_COLOR_SYSTEM", "auto")
 """Force color system override"""
+
+TEXTUAL_ANIMATIONS: AnimationLevel = _get_textual_animations()
+"""Determines whether animations run or not."""

src/textual/css/scalar_animation.py

@@ -3,7 +3,7 @@
 from typing import TYPE_CHECKING
 
 from .._animator import Animation, EasingFunction
-from .._types import CallbackType
+from .._types import AnimationLevel, CallbackType
 from .scalar import Scalar, ScalarOffset
 
 if TYPE_CHECKING:
@@ -23,6 +23,7 @@ def __init__(
         speed: float | None,
         easing: EasingFunction,
         on_complete: CallbackType | None = None,
+        level: AnimationLevel = "full",
     ):
         assert (
             speed is not None or duration is not None
@@ -34,6 +35,7 @@ def __init__(
         self.final_value = value
         self.easing = easing
         self.on_complete = on_complete
+        self.level = level
 
         size = widget.outer_size
         viewport = widget.app.size
@@ -48,11 +50,18 @@ def __init__(
             assert duration is not None, "Duration expected to be non-None"
             self.duration = duration
 
-    def __call__(self, time: float) -> bool:
+    def __call__(
+        self, time: float, app_animation_level: AnimationLevel = "full"
+    ) -> bool:
         factor = min(1.0, (time - self.start_time) / self.duration)
         eased_factor = self.easing(factor)
 
-        if eased_factor >= 1:
+        if (
+            eased_factor >= 1
+            or app_animation_level == "none"
+            or app_animation_level == "basic"
+            and self.level == "full"
+        ):
             setattr(self.styles, self.attribute, self.final_value)
             return True