TweenAvalonia

Avalonia XAML Transitions cannot be stopped, completed or awaited and give no completion callback. For anything beyond a simple hover you end up writing timers or fighting the framework.

The goal was a small library that feels like PrimeTween: only target and end value required, sensible defaults, but every animation returns a handle you control. It is already used in Xenia Manager Big Screen Mode for fades and transitions.

• One shared ticker A single UI thread ticker drives every tween and sleeps while idle. No per animation timers and no setup call.
• Handles that cannot go stale Public Tween is a versioned struct over pooled instances. Stopping a tween releases it and bumps the version so old handles are harmless.
• Latest wins superseding A new tween on the same target and property stops the previous one. StopAll and CompleteAll work on the same table.
• Typed factories Factories for double, float, int, Color, Point, Vector, Thickness and Rect plus sugar for Opacity, Color, Margin, Width and Height. Unsupported types throw at creation.
• Zero allocation hot paths Pooled instances, struct awaiter, cached target based callbacks and no boxing on per frame writes. Guarded by allocation tests.
• Small ergonomic defaults Only target and end value required. Defaults to 1s and SineEaseInOut. TweenSettings bundles can be reused and DefaultEasing is settable.