Function onFrame

onFrame(widget: Widget, callback: () => boolean): CancelHandle
Calls a callback on every frame tick, synchronised to the widget's GDK frame clock.

The callback should return true to continue receiving frame updates, or false to stop. The animation is automatically cancelled when the widget is destroyed.
Parameters
- widget: Widget
  The widget whose frame clock should drive the animation
- callback: () => boolean
  Called on each frame. Return false to stop.
Returns CancelHandle
A CancelHandle to cancel the animation externally
Example
```
const handle = onFrame(myWidget, () => {
    opacity -= 0.02;
    myWidget.opacity = opacity;
    return opacity > 0;
});
```
- Defined in src/utils/timeout.ts:98