Changed
- Display board markers only redraw when an aircraft actually changed.
The follow-up to the last release's kiosk profiling: with the photo rail
quiet, the largest remaining cost on a Raspberry Pi wall display was the
radar markers — every data refresh rebuilt every marker's icon and
position, and every photo/route/owner lookup that resolved triggered
another full pass, whether or not anything on screen was different. The
board now diffs first: a marker's icon is rebuilt only when its rendered
content actually changed (position, altitude color, heading, label,
badge, selection halo), and its position is rewritten only when the
aircraft moved. Measured on identical back-to-back refreshes: marker DOM
writes went from roughly seventy-five per second to zero, and a change to
a single aircraft touches exactly that one marker. Visually nothing is
different — this is headroom for busy days, when the marker cost scales
with every extra aircraft overhead.