Function hover_fades_active 

pub fn hover_fades_active() -> bool

Frame-drive hook: call ONCE per window frame, from the app’s root render:

if motion::hover_fades_active() {
    window.request_animation_frame();
}

Not optional. A hover fade is a colour computed at paint time rather than an animation element that drives itself: hover_listener dirties the window once as the pointer crosses, and every frame after that one has to be asked for. An app that skips this paints the blend’s first frame — at rest — and then holds it until something unrelated repaints, which looks like a wash that sticks and then jumps rather than one that is simply off.

It is also the tick: the frame counter it advances is what evicts fades whose elements have gone away, so skipping it leaks an entry per hovered element.