transitionProgress property
double
get
transitionProgress
How far through a theme transition this is, 0..1; 1 at rest. Shared across the theme: it's the progress that lerps backgroundTone, contrast and scale. Retargeting mid-transition restarts it at 0 from what was visible.
For values derived from two endpoints, e.g. a border solved once for the theme before and once for target: lerp by this instead of solving per frame.
Implementation
double get transitionProgress => 1;