reply_json.h File Reference

Formats the /commands JSON reply from the tracker snapshot and the controller status (pure C++20, natively tested). More...

#include "calibration_session.h"
#include "control_status.h"
#include "track_snapshot.h"
#include <cstddef>
#include <cstdint>

Go to the source code of this file.

Classes
struct	hud::ReplyInput
	Inputs of one reply. Null pointers mean that part is not available. More...

Functions
size_t	hud::format_reply (const ReplyInput &in, char *out, size_t size)
	Writes the NUL-terminated JSON reply into out and returns its length (without the NUL).
const char *	hud::cal_state_name (aiming::CalState st)
	Wire name of a calibration state: idle, point1, point2, done or failed.
const char *	hud::speed_name (uint8_t speed)
	Wire name of ControlStatus::speed: slow (0), normal (1) or fast (2); anything else reads as normal.

Variables
constexpr size_t	hud::kReplySize = 832
	Buffer size that always holds a full reply.

Detailed Description

Formats the /commands JSON reply from the tracker snapshot and the controller status (pure C++20, natively tested).

No Arduino or ESP-IDF headers and no heap use: the output goes into a caller buffer (the httpd task's stack). The existing keys keep their order and format so older HUDs keep working; the keys added by the HUD overhaul follow them (see docs/superpowers/specs/2026-10-26-hud-ux-overhaul-design.md, section "Reply JSON").

Function Documentation

format_reply()

size_t hud::format_reply	(	const ReplyInput &	in,
		char *	out,
		size_t	size )

Writes the NUL-terminated JSON reply into out and returns its length (without the NUL).

Without a track the fixed fallback {"detected":0,"x":0,"y":0,"width":320,"height":240,"pixels":0} is written. With a track the tracker keys follow, then, when a status is present, the controller keys (mode, cal, cal_state, calibrated, pan, tilt, cal_error, cal_saves, cal_miss, stick, ax, ay, lim, rx0, ry0, rx1, ry1, home, ret, spd) and finally vw. If everything does not fit in size bytes the reply is {"detected":0}; below 15 bytes not even that fits and an empty string (length 0) is written.

Variable Documentation

kReplySize

size_t hud::kReplySize = 832

constexpr

Buffer size that always holds a full reply.

test_reply_json formats the worst case (every counter at its maximum, every int16 negative, every float at FLT_MAX width, the longest calibration error text; 739 bytes) and asserts it is shorter than this with at least 64 bytes to spare. A reply that still does not fit falls back to {"detected":0}.