scroll view

Author: willmcgugan

src/textual/animator.py

@@ -0,0 +1,81 @@
+from __future__ import annotations
+
+import logging
+from .message_pump import MessagePump
+from ._timer import Timer
+from time import time
+from typing import Callable
+
+from dataclasses import dataclass
+
+
+EasingFunction = Callable[[float], float]
+
+LinearEasing = lambda value: value
+
+
+def InOutCubitEasing(x: float) -> float:
+    return 4 * x * x * x if x < 0.5 else 1 - pow(-2 * x + 2, 3) / 2
+
+
+log = logging.getLogger("rich")
+
+
+@dataclass
+class Animation:
+    attribute: str
+    start_time: float
+    duration: float
+    start_value: float
+    end_value: float
+    easing_function: EasingFunction
+
+    def __call__(self, obj: object, time: float) -> bool:
+        progress = min(1.0, (time - self.start_time) / self.duration)
+        eased_progress = self.easing_function(progress)
+        value = self.start_value + (self.end_value - self.start_value) * eased_progress
+        setattr(obj, self.attribute, value)
+        return value == self.end_value
+
+
+class Animator:
+    def __init__(self, obj: MessagePump) -> None:
+        self.obj = obj
+        self._animations: dict[str, Animation] = {}
+        self._timer: Timer | None = None
+
+    def animate(
+        self,
+        attribute: str,
+        value: float,
+        duration: float = 1,
+        easing: EasingFunction = InOutCubitEasing,
+    ) -> None:
+        start_value = getattr(self.obj, attribute)
+        start_time = time()
+
+        animation = Animation(
+            attribute=attribute,
+            start_time=start_time,
+            duration=duration,
+            start_value=start_value,
+            end_value=value,
+            easing_function=easing,
+        )
+        self._animations[attribute] = animation
+        if self._timer is None:
+            self._timer = self.obj.set_interval(0.02, callback=self)
+
+    async def __call__(self) -> None:
+        log.debug("ANIMATION FRAME")
+        animation_time = time()
+        if all(
+            animation(self.obj, animation_time)
+            for animation in self._animations.values()
+        ):
+            if self._timer is not None:
+                self._timer.stop()
+                self._timer = None
+
+        for _attribute, animation in self._animations.items():
+            animation(self.obj, animation_time)

src/textual/widgets/scroll_view.py

@@ -69,6 +69,6 @@ async def on_key(self, event: events.Key) -> None:
         elif event.key == "up":
             self.y -= 1
         elif event.key == "pagedown":
-            self._animator.animate("y", self.y + self.size.height, duration=0.5)
+            self._animator.animate("y", self.y + self.size.height, duration=1)
         elif event.key == "pageup":
-            self._animator.animate("y", self.y - self.size.height, duration=0.5)
+            self._animator.animate("y", self.y - self.size.height, duration=1)