Animation callback (#683)

* Add on_complete callback to Animations

* Add tests for on_complete Animation callbacks

* Update __textual_animation__ signature to include callback

* Support awaitable callbacks for animator on_complete

* Import tidying

* Update animator tests

sandbox/darren/just_a_box.py

@@ -1,11 +1,11 @@
 from __future__ import annotations
 
+import asyncio
+
 from rich.console import RenderableType
-from rich.panel import Panel
 
 from textual import events
 from textual.app import App, ComposeResult
-from textual.layout import Horizontal, Vertical
 from textual.widget import Widget
 
 
@@ -18,37 +18,22 @@ class Box(Widget, can_focus=True):
         super().__init__(*children, id=id, classes=classes)
 
     def render(self) -> RenderableType:
-        return Panel("Box")
+        return "Box"
 
 
 class JustABox(App):
     def compose(self) -> ComposeResult:
-        yield Horizontal(
-            Vertical(
-                Box(id="box1", classes="box"),
-                Box(id="box2", classes="box"),
-                # Box(id="box3", classes="box"),
-                # Box(id="box4", classes="box"),
-                # Box(id="box5", classes="box"),
-                # Box(id="box6", classes="box"),
-                # Box(id="box7", classes="box"),
-                # Box(id="box8", classes="box"),
-                # Box(id="box9", classes="box"),
-                # Box(id="box10", classes="box"),
-                id="left_pane",
-            ),
-            Box(id="middle_pane"),
-            Vertical(
-                Box(id="boxa", classes="box"),
-                Box(id="boxb", classes="box"),
-                Box(id="boxc", classes="box"),
-                id="right_pane",
-            ),
-            id="horizontal",
-        )
+        self.box = Box()
+        yield self.box
 
-    def key_p(self):
-        print(self.query("#horizontal").first().styles.layout)
+    def key_a(self):
+        self.animator.animate(
+            self.box.styles,
+            "opacity",
+            value=0.0,
+            duration=2.0,
+            on_complete=self.box.remove,
+        )
 
     async def on_key(self, event: events.Key) -> None:
         await self.dispatch_key(event)

src/textual/_animator.py

@@ -8,9 +8,10 @@ from typing import Any, Callable, TypeVar
 from dataclasses import dataclass
 
 from . import _clock
+from ._callback import invoke
 from ._easing import DEFAULT_EASING, EASING
 from ._timer import Timer
-from ._types import MessageTarget
+from ._types import MessageTarget, CallbackType
 
 if sys.version_info >= (3, 8):
     from typing import Protocol, runtime_checkable
@@ -30,8 +31,20 @@ class Animatable(Protocol):
 
 
 class Animation(ABC):
+
+    on_complete: CallbackType | None = None
+    """Callback to run after animation completes"""
+
     @abstractmethod
     def __call__(self, time: float) -> bool:  # pragma: no cover
+        """Call the animation, return a boolean indicating whether animation is in-progress or complete.
+
+        Args:
+            time (float): The current timestamp
+
+        Returns:
+            bool: True if the animation has finished, otherwise False.
+        """
         raise NotImplementedError("")
 
     def __eq__(self, other: object) -> bool:
@@ -48,6 +61,7 @@ class SimpleAnimation(Animation):
     end_value: float | Animatable
     final_value: object
     easing: EasingFunction
+    on_complete: CallbackType | None = None
 
     def __call__(self, time: float) -> bool:
 
@@ -109,6 +123,7 @@ class BoundAnimator:
         duration: float | None = None,
         speed: float | None = None,
         easing: EasingFunction | str = DEFAULT_EASING,
+        on_complete: CallbackType | None = None,
     ) -> None:
         easing_function = EASING[easing] if isinstance(easing, str) else easing
         return self._animator.animate(
@@ -119,6 +134,7 @@ class BoundAnimator:
             duration=duration,
             speed=speed,
             easing=easing_function,
+            on_complete=on_complete,
         )
 
 
@@ -163,6 +179,7 @@ class Animator:
         duration: float | None = None,
         speed: float | None = None,
         easing: EasingFunction | str = DEFAULT_EASING,
+        on_complete: CallbackType | None = None,
     ) -> None:
         """Animate an attribute to a new value.
 
@@ -201,6 +218,7 @@ class Animator:
                 duration=duration,
                 speed=speed,
                 easing=easing_function,
+                on_complete=on_complete,
             )
         if animation is None:
             start_value = getattr(obj, attribute)
@@ -223,6 +241,7 @@ class Animator:
                 end_value=value,
                 final_value=final_value,
                 easing=easing_function,
+                on_complete=on_complete,
             )
         assert animation is not None, "animation expected to be non-None"
 
@@ -233,7 +252,7 @@ class Animator:
         self._animations[animation_key] = animation
         self._timer.resume()
 
-    def __call__(self) -> None:
+    async def __call__(self) -> None:
         if not self._animations:
             self._timer.pause()
         else:
@@ -241,7 +260,11 @@ class Animator:
             animation_keys = list(self._animations.keys())
             for animation_key in animation_keys:
                 animation = self._animations[animation_key]
-                if animation(animation_time):
+                animation_complete = animation(animation_time)
+                if animation_complete:
+                    completion_callback = animation.on_complete
+                    if completion_callback is not None:
+                        await invoke(completion_callback)
                     del self._animations[animation_key]
 
     def _get_time(self) -> float:

src/textual/_types.py

@@ -1,5 +1,6 @@
 import sys
-from typing import Awaitable, Callable, List, Optional, TYPE_CHECKING
+from typing import Awaitable, Callable, List, TYPE_CHECKING, Union
+
 from rich.segment import Segment
 
 if sys.version_info >= (3, 8):
@@ -11,8 +12,6 @@ else:
 if TYPE_CHECKING:
     from .message import Message
 
-Callback = Callable[[], None]
-
 
 class MessageTarget(Protocol):
     async def post_message(self, message: "Message") -> bool:
@@ -34,5 +33,5 @@ class EventTarget(Protocol):
 
 
 MessageHandler = Callable[["Message"], Awaitable]
-
 Lines = List[List[Segment]]
+CallbackType = Union[Callable[[], Awaitable[None]], Callable[[], None]]

src/textual/css/scalar_animation.py

@@ -1,8 +1,8 @@
 from __future__ import annotations
 
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Callable
 
-from .. import events, log
+from .._types import CallbackType
 from ..geometry import Offset
 from .._animator import Animation
 from .scalar import ScalarOffset
@@ -25,6 +25,7 @@ class ScalarAnimation(Animation):
         duration: float | None,
         speed: float | None,
         easing: EasingFunction,
+        on_complete: CallbackType | None = None,
     ):
         assert (
             speed is not None or duration is not None
@@ -35,6 +36,7 @@ class ScalarAnimation(Animation):
         self.attribute = attribute
         self.final_value = value
         self.easing = easing
+        self.on_complete = on_complete
 
         size = widget.outer_size
         viewport = widget.app.size
@@ -55,7 +57,6 @@ class ScalarAnimation(Animation):
         eased_factor = self.easing(factor)
 
         if eased_factor >= 1:
-            offset = self.final_value
             setattr(self.styles, self.attribute, self.final_value)
             return True
 

src/textual/css/styles.py

@@ -10,6 +10,7 @@ from typing import TYPE_CHECKING, Any, Iterable, NamedTuple, cast
 import rich.repr
 from rich.style import Style
 
+from textual._types import CallbackType
 from .._animator import Animation, EasingFunction
 from ..color import Color
 from ..geometry import Offset, Spacing
@@ -579,9 +580,9 @@ class Styles(StylesBase):
         duration: float | None,
         speed: float | None,
         easing: EasingFunction,
+        on_complete: CallbackType | None = None,
     ) -> Animation | None:
-        from ..widget import Widget
-
+        # from ..widget import Widget
         # node = self.node
         # assert isinstance(self.node, Widget)
         if isinstance(value, ScalarOffset):
@@ -594,6 +595,7 @@ class Styles(StylesBase):
                 duration=duration,
                 speed=speed,
                 easing=easing,
+                on_complete=on_complete,
             )
         return None
 

src/textual/messages.py

@@ -1,8 +1,9 @@
 from __future__ import annotations
-from typing import TYPE_CHECKING, Callable, Awaitable, Union
+from typing import TYPE_CHECKING
 
 import rich.repr
 
+from ._types import CallbackType
 from .message import Message
 
 
@@ -11,9 +12,6 @@ if TYPE_CHECKING:
     from .widget import Widget
 
 
-CallbackType = Union[Callable[[], Awaitable[None]], Callable[[], None]]
-
-
 @rich.repr.auto
 class Update(Message, verbosity=3):
     def __init__(self, sender: MessagePump, widget: Widget):

src/textual/screen.py

@@ -12,7 +12,7 @@ from ._callback import invoke
 
 from .geometry import Offset, Region, Size
 from ._compositor import Compositor, MapGeometry
-from .messages import CallbackType
+from ._types import CallbackType
 from .reactive import Reactive
 from .renderables.blank import Blank
 from ._timer import Timer

tests/test_animator.py

@@ -1,12 +1,10 @@
 from __future__ import annotations
 
-
 from dataclasses import dataclass
 from unittest.mock import Mock
 
 import pytest
 
-
 from textual._animator import Animator, SimpleAnimation
 from textual._easing import EASING, DEFAULT_EASING
 
@@ -184,8 +182,7 @@ class MockAnimator(Animator):
         return self._time
 
 
-def test_animator():
-
+async def test_animator():
     target = Mock()
     animator = MockAnimator(target)
     animate_test = AnimateTest()
@@ -206,11 +203,11 @@ def test_animator():
     assert animator._animations[(id(animate_test), "foo")] == expected
     assert not animator._on_animation_frame_called
 
-    animator()
+    await animator()
     assert animate_test.foo == 0
 
     animator._time = 5
-    animator()
+    await animator()
     assert animate_test.foo == 50
 
     # New animation in the middle of an existing one
@@ -218,12 +215,11 @@ def test_animator():
     assert animate_test.foo == 50
 
     animator._time = 6
-    animator()
+    await animator()
     assert animate_test.foo == 200
 
 
 def test_bound_animator():
-
     target = Mock()
     animator = MockAnimator(target)
     animate_test = AnimateTest()
@@ -245,3 +241,29 @@ def test_bound_animator():
         easing=EASING[DEFAULT_EASING],
     )
     assert animator._animations[(id(animate_test), "foo")] == expected
+
+
+def test_animator_on_complete_callback_not_fired_before_duration_ends():
+    callback = Mock()
+    animate_test = AnimateTest()
+    animator = MockAnimator(Mock())
+
+    animator.animate(animate_test, "foo", 200, duration=10, on_complete=callback)
+
+    animator._time = 9
+    animator()
+
+    assert not callback.called
+
+
+async def test_animator_on_complete_callback_fired_at_duration():
+    callback = Mock()
+    animate_test = AnimateTest()
+    animator = MockAnimator(Mock())
+
+    animator.animate(animate_test, "foo", 200, duration=10, on_complete=callback)
+
+    animator._time = 10
+    await animator()
+
+    callback.assert_called_once_with()