thumbnailOpacity static method
Thumbnail selector bar opacity.
Visible at progress < 0.4, fades out linearly.
opacity = 1 - progress * 2 (clamped to 0.0–1.0).
Implementation
static double thumbnailOpacity(double progress) {
final t = progress.clamp(0.0, 1.0);
return (1.0 - t * 2.5).clamp(0.0, 1.0);
}