The store

An aircraft's effects read its flight sixty times a second or more. If that flight were React state, every write would render the tree under it, and a flight model writes every frame. So it is not.

One object, written in placeCopy Anchor Link

flight.values is created once, with the flight, and never replaced. set writes into it. Any reader can take the object once and read it whenever, for the cost of a property access, with nothing allocated in the frame.

The price is that a reader can't tell a new value by its identity. That is what the version is for.

The versionCopy Anchor Link

Every write that changed something adds one to flight.version. A write that changed nothing leaves it alone, and calls no listener.

Each effect remembers the flight and the version it last read. In its frame it compares them, and when neither moved it does none of its own work:

• the afterburner batch reads the throttles, and rewrites its profile's altitude, airspeed and temperature offset, only then;
• the vapor copies the airspeed, the angles and the air only then, the altitude rounded to 10 m so a climb doesn't rebuild its condensation table every frame;
• the control rig works out the parts' targets only then.

A flight held still costs every effect one comparison a frame.

What follows from a writeCopy Anchor Link

set writes the fields it is given, then works out what follows. The speeds (Mach, dynamic pressure, ram pressure) are a few multiplications, done on every change. The air is a standard atmosphere and a saturation pressure, done only when the altitude, the day's offset or the humidity is not what it was last worked out for.

Rendering on purposeCopy Anchor Link

useFlight is the one way in for React. It is useSyncExternalStore over subscribe, with two guards:

• the selection is compared, so a write that leaves it the same renders nothing;
• hz holds back the notifications to at most that many a second, firing the last one at the end of a gap so the final value always arrives.

A HUD that rounds its Mach to two places at 10 Hz renders at most ten times a second, and not at all when the number on screen would be the same.

Who goes firstCopy Anchor Link

Inside the Canvas, the tracker runs at frame priority −1. The control rig and every effect run at 0 or later, or read the flight where they draw. Each frame, everything reads the flight as it was tracked in that frame, not the one before.