D-pad navigation on Android TV felt sluggish next to Projectivy and the
Fire TV launcher: every step of the home rail and hub rows trailed the
focus border in a 500ms ease-out, and hub moves deferred the vertical
glide by a frame. The 500ms was measured from the tvOS focus engine
(f357be407) and applied to every platform; Leanback prices a one-card
step at roughly 100-150ms, so the same glide reads as input lag on a
D-pad.
FocusTheme.navigationScrollDuration now vends the per-platform value:
Apple TV keeps the measured 500ms, everything else glides in 150ms.
TvBrowseRail and HubSection use it for row and hub-list scrolls, and a
hub move starts the vertical animation in the same frame when the
build-time section offsets are already known.
Measured with screen recordings on a Shield TV (2019) and a Fire TV
Stick 4K Max: row motion per press 470-510ms before, 135-150ms after;
hub move 480ms before, 120-150ms after.
edde746
5bd742c8b8