feat: add spinner widget which doesn't trigger whole screen renders a…

…nd uses new local renders of headless-kivy

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Upcoming
 
 - chore: migrate from poetry to uv for the sake of improving performance and dealing with conflicting sub-dependencies
+- feat: add spinner widget which doesn't trigger whole screen renders and uses new local renders of headless-kivy
 
 ## Version 0.13.3
 

ubo_gui/spinner/__init__.py

@@ -0,0 +1,48 @@
+"""Spinner widget for loading indication."""
+
+from __future__ import annotations
+
+import math
+from typing import Any, cast
+
+from headless_kivy import HeadlessWidget
+from kivy.clock import Clock
+from kivy.graphics.context_instructions import Rotate
+from kivy.properties import NumericProperty
+from kivy.uix.label import Label
+
+
+class SpinnerWidget(HeadlessWidget):
+    """Spinner widget for loading indication."""
+
+    angle = NumericProperty(0)
+
+    def __init__(self: SpinnerWidget, **kwargs: object) -> None:
+        """Initialize the SpinnerWidget class."""
+        super().__init__(**cast(Any, kwargs))
+        self.interval = Clock.schedule_interval(self.rotate_spinner, 1 / 40)
+        self.label = Label(
+            text='',
+            color=(1, 1, 1),
+        )
+        self.label.bind(texture_size=self.label.setter('size'))
+        self.bind(
+            size=lambda *_: self.label.setter('center')(
+                self.label,
+                (self.width / 2, self.height / 2),
+            ),
+        )
+        self.add_widget(self.label)
+
+    def __del__(self: SpinnerWidget) -> None:
+        """Remove the spinner widget."""
+        self.interval.cancel()
+
+    def rotate_spinner(self: SpinnerWidget, dt: float) -> None:
+        """Rotate the spinner."""
+        self.angle = (self.angle + dt) % math.tau
+        with self.label.canvas.before:
+            Rotate(
+                angle=-dt * 400,
+                origin=self.label.center,
+            )