Get the AF frame position
Return the camera’s current autofocus frame(s) — position, size and focus state — so a client can draw a focus box over a live view.
Each frame reports its centre three ways: normalized (0-1, the value to
use for overlays at any resolution), position (the same point in the
coordinate space setAFAreaPosition expects, so a read can be written
straight back), and raw (the camera’s own numerator/denominator pair).
size.normalized_width / normalized_height give the box dimensions as a
fraction of the frame.
More than one frame can be returned. An expanding area reports the
main box plus its assist box — an ILCE-7M4 set to Tracking Expand Flexible
Spot returns a 38x38 contrast-flexible-main and a 76x76
contrast-flexible-assist. Draw them all.
state (focused, not-focused, moving, selection, …) is the value
to drive box colour from.
When this returns 400
The camera only reports a frame for focus areas that actually draw a box — Flexible Spot, Expand Flexible Spot, Tracking variants. In Wide or a face/eye-priority mode there is no movable frame and nothing is reported. Live view should be streaming, since this reads a live-view property.

