Function paint_held_readout 

pub fn paint_held_readout(
    scene: &mut Scene,
    transform: Affine,
    text: &mut TextRenderer,
    theme: &Theme,
    face: &SliderFace,
    label: &str,
)

The value a held knob would land on, label, on a chip above the knob, kept over the slider’s own span so it never leaves the control it reads. The one readout every held slider shows: the retained Slider and an immediate-mode seek bar (a shell card’s) alike.