trx-rs/UI-CAPS.md

UI Capability Gating

This document specifies how trx-client's HTTP frontend adapts its controls to the capabilities of the connected rig backend. Devices such as SDR receivers expose filter controls but not TX controls; traditional transceivers are the reverse.

---

Progress

For AI agents: This section is the single source of truth for implementation status. Each task has a unique ID (e.g. UC-01), a status badge, a description, the files it touches, and any blocking dependencies.

Status legend: [ ] not started · [~] in progress · [x] done · [!] blocked

Foundational (parallel)

ID	Status	Task	Files	Needs
UC-01	[ ]	Extend RigCapabilities with tx, tx_limit, vfo_switch, filter_controls, signal_meter bool flags	src/trx-core/src/rig/state.rs	—
UC-02	[ ]	Update capability declarations in all backends to set new flags	src/trx-server/trx-backend/trx-backend-ft817/src/lib.rs, trx-backend-ft450d/src/lib.rs, trx-backend-soapysdr/src/lib.rs	UC-01
UC-03	[ ]	Add RigFilterState struct; add filter: Option<RigFilterState> to RigSnapshot; populate from SDR rig state	src/trx-core/src/rig/state.rs, src/trx-server/trx-backend/trx-backend-soapysdr/src/lib.rs	—
UC-04	[ ]	Add SetBandwidth, SetFirTaps to ClientCommand; add mapping arms; update rig_task.rs to dispatch them	src/trx-protocol/src/types.rs, mapping.rs, src/trx-server/src/rig_task.rs	UC-03

HTTP layer

ID	Status	Task	Files	Needs
UC-05	[ ]	Add /set_bandwidth and /set_fir_taps HTTP endpoints	src/trx-client/trx-frontend/trx-frontend-http/src/api.rs	UC-04

Frontend

ID	Status	Task	Files	Needs
UC-06	[ ]	Read state.info.capabilities on each SSE event; toggle visibility of TX controls, meter rows, VFO button, lock button	assets/web/app.js	UC-01, UC-02
UC-07	[ ]	Add "Filters" control panel (bandwidth, FIR taps, CW tone Hz); show only when capabilities.filter_controls	assets/web/index.html, assets/web/app.js	UC-05, UC-06

Tests

ID	Status	Task	Files	Needs
UC-08	[ ]	Unit tests: SDR backend declares tx=false, filter_controls=true; FT-817/450D declare tx=true, filter_controls=false	src/trx-server/trx-backend/trx-backend-soapysdr/src/lib.rs, trx-backend-ft817, trx-backend-ft450d	UC-02
UC-09	[ ]	Protocol round-trip test: RigSnapshot serialises filter field when Some, omits it when None	src/trx-protocol/src/codec.rs or types.rs	UC-03

---

Goals

• All UI control groups are shown/hidden purely from RigCapabilities flags received in the initial GET /status and each SSE status event — no hard-coding per model name
• SDR backends show filter controls (bandwidth, FIR taps, CW tone); hide TX controls (PTT, power, TX limit, TX meters, TX audio)
• Transceiver backends show TX controls; hide filter controls
• Adding a new backend requires only setting the right capability flags — no frontend changes

---

Non-Goals

• Per-channel filter control (multi-channel SDR tuning) — out of scope; only the primary channel is exposed here
• Dynamic capability changes at runtime (capability flags are set once at rig init and treated as static)
• Changing the rigctl or http-json frontends (HTTP frontend only)

---

Capability Flags

New flags added to RigCapabilities (UC-01)

Flag	Type	Meaning
tx	bool	Backend supports transmit: PTT, power on/off, TX meters, TX audio
tx_limit	bool	Backend supports get_tx_limit / set_tx_limit
vfo_switch	bool	Backend supports toggle_vfo
filter_controls	bool	Backend supports runtime filter adjustment (bandwidth, FIR taps)
signal_meter	bool	Backend returns a meaningful RX signal strength value

Existing flags lock and lockable are unchanged.

Backend declarations (UC-02)

Backend	tx	tx_limit	vfo_switch	filter_controls	signal_meter	lock/lockable
FT-817	✓	✓	✓	✗	✓	✓ / ✓
FT-450D	✓	✓	✓	✗	✓	✓ / ✓
SoapySDR	✗	✗	✗	✓	✓	✗ / ✗

---

Filter State

RigFilterState struct (UC-03)

Added to trx-core/src/rig/state.rs:

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct RigFilterState {
    pub bandwidth_hz: u32,      // Audio bandwidth of primary channel
    pub fir_taps: u32,          // FIR filter tap count
    pub cw_center_hz: u32,      // CW tone centre frequency (audio domain)
}

Added to RigSnapshot:

#[serde(default, skip_serializing_if = "Option::is_none")]
pub filter: Option<RigFilterState>,

The SDR backend populates this from the primary channel's live DSP state. All other backends leave it None.

---

New Protocol Commands

ClientCommand additions (UC-04)

SetBandwidth { bandwidth_hz: u32 },
SetFirTaps   { taps: u32 },

SetCwToneHz already exists and is reused.

Mapping (UC-04)

ClientCommand::SetBandwidth { bandwidth_hz } =>
    RigCommand::SetBandwidth(bandwidth_hz),
ClientCommand::SetFirTaps { taps } =>
    RigCommand::SetFirTaps(taps),

The SDR backend applies changes to the live DSP chain immediately. Other backends return RigError::not_supported(...).

---

New HTTP Endpoints (UC-05)

Endpoint	Method	Query param	Action
/set_bandwidth	POST	hz: u32	Sets primary channel audio bandwidth
/set_fir_taps	POST	taps: u32	Sets primary channel FIR tap count

---

Frontend Visibility Map (UC-06, UC-07)

UI element / group	Shown when
PTT button	capabilities.tx
Power button	capabilities.tx
TX meters (power bar, SWR bar)	capabilities.tx && state.status.tx_en
TX Limit row	capabilities.tx_limit
TX Audio toggle + volume	capabilities.tx
VFO selector buttons	capabilities.vfo_switch
Lock button	capabilities.lock
Signal meter	capabilities.signal_meter
Filters panel	capabilities.filter_controls

Visibility is applied in a single applyCapabilities(caps) function called from the SSE status handler, using element.classList.toggle('hidden', !condition).

Filter panel layout (UC-07)

┌─ Filters ──────────────────────────────────┐
│  Bandwidth  [──────●──────] 3000 Hz        │
│  FIR taps   [32 ▾] (32 / 64 / 128 / 256)  │
│  CW tone    [──●───────────] 700 Hz        │
└────────────────────────────────────────────┘

Each control dispatches to its REST endpoint on change/input (debounced 200 ms). The panel is hidden by default (class="hidden") and revealed when capabilities.filter_controls is set.

---

Implementation Notes

• applyCapabilities() must run before the first paint (call it synchronously on the initial /status response, not only on SSE events) to avoid layout flash of unsupported controls.
• hidden CSS class should set display: none and aria-hidden: true.
• The existing set_cw_tone endpoint and CW decoder panel remain in the CW decoder tab — they are decoder settings, not filter settings. The Filters panel bandwidth/taps apply to the DSP chain; CW tone moves to both places or is de-duplicated in a follow-up.
• If a future backend supports TX but not tx_limit, only the TX Limit row is hidden; PTT remains.