Add on_complete callback to Animations

sandbox/darren/just_a_box.py

@@ -1,11 +1,9 @@
 from __future__ import annotations
 
 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 +16,22 @@ 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

@@ -30,8 +30,20 @@ class Animatable(Protocol):
 
 
 class Animation(ABC):
+
+    on_complete: Callable[[], None] | 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 +60,7 @@ class SimpleAnimation(Animation):
     end_value: float | Animatable
     final_value: object
     easing: EasingFunction
+    on_complete: Callable[[], None] | None = None
 
     def __call__(self, time: float) -> bool:
 
@@ -109,6 +122,7 @@ class BoundAnimator:
         duration: float | None = None,
         speed: float | None = None,
         easing: EasingFunction | str = DEFAULT_EASING,
+        on_complete: Callable[[], None] | None = None,
     ) -> None:
         easing_function = EASING[easing] if isinstance(easing, str) else easing
         return self._animator.animate(
@@ -119,6 +133,7 @@ class BoundAnimator:
             duration=duration,
             speed=speed,
             easing=easing_function,
+            on_complete=on_complete,
         )
 
 
@@ -163,6 +178,7 @@ class Animator:
         duration: float | None = None,
         speed: float | None = None,
         easing: EasingFunction | str = DEFAULT_EASING,
+        on_complete: Callable[[], None] | None = None,
     ) -> None:
         """Animate an attribute to a new value.
 
@@ -201,6 +217,7 @@ class Animator:
                 duration=duration,
                 speed=speed,
                 easing=easing_function,
+                on_complete=on_complete,
             )
         if animation is None:
             start_value = getattr(obj, attribute)
@@ -223,6 +240,7 @@ 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"
 
@@ -241,7 +259,11 @@ 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:
+                        completion_callback()
                     del self._animations[animation_key]
 
     def _get_time(self) -> float:

src/textual/css/scalar_animation.py

@@ -1,8 +1,7 @@
 from __future__ import annotations
 
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Callable
 
-from .. import events, log
 from ..geometry import Offset
 from .._animator import Animation
 from .scalar import ScalarOffset
@@ -25,6 +24,7 @@ class ScalarAnimation(Animation):
         duration: float | None,
         speed: float | None,
         easing: EasingFunction,
+        on_complete: Callable[[], None] | None = None,
     ):
         assert (
             speed is not None or duration is not None
@@ -35,6 +35,7 @@ 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 +56,6 @@ 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