mxaccessgw/docs/AlarmClientDiscovery.md

# aaAlarmManagedClient discovery — public surface, 2026-05-01

Result of running
`MxGateway.Worker.Tests.AlarmClientDiscoveryTests.DumpAlarmClientPublicSurface`
against the deployed AVEVA assembly:

- File:
  `C:\Program Files (x86)\ArchestrA\Framework\Bin\ViewAppFramework\Content\MA\aaAlarmManagedClient.dll`
- Assembly identity: `aaAlarmManagedClient, Version=1.0.7368.41290,
  Culture=neutral, PublicKeyToken=7ebd82b507d9e10c`

## Public types

- `aaAlarmManagedClient.AlarmClient` (class)
- `aaAlarmManagedClient.PriorityData` (class)

That's the entire exported surface — two types, no interfaces, no
delegates.

## `AlarmClient` events

**None.** The class has no public events at all. The reflection probe's
`GetEvents(BindingFlags.Public | Instance | Static)` returned an empty
list.

## `AlarmClient` methods (relevant subset)

- **Lifecycle:**
  `RegisterConsumer(int hWnd, string szProductName, string
  szApplicationName, string szVersion, bool bRetainHiddenAlarms) → int`,
  `DeregisterConsumer() → int`,
  `InitializeConsumer(string szApplicationName) → int`,
  `UninitializeConsumer() → int`,
  `Dispose()`.
- **Subscription:**
  `Subscribe(string szSubscription, short wFromPri, short wToPri,
  eQueryType QueryType, eSortFlags SortFlags, eAlarmFilterState
  FilterMask, eAlarmFilterState FilterSpecification) → int`.
- **Change enumeration (pull on poke):**
  `GetStatistics(out int lPercentQuery, out int lTotalAlarms, out int
  lActiveAlarms, out int lSuppressedAlarms, out int lSuppressedFilters,
  out int lNewAlarms, out int lChangesCount, out int[] ChangeCodes,
  out int[] ChangePos, out int[] hAlarm) → int`.
- **Record fetch:**
  `GetAlarmExtendedRec(int lIndex, out AlarmRecord almRec) → int`,
  `GetAlarmExtendedRec2(...)`,
  `GetHighPriAlarm(out AlarmRecord almRec) → int`.
- **Selection model** (used by ack-selected-* family):
  `DeselectAll`, `SelectAlaramEntry(short select, int from, int to)`,
  `SelectByGUID(Guid)`, `SelectAlarmCount(int from, int to)`.
- **Acknowledge:**
  `AlarmAckByGUID(Guid alarmGuid, string ackComment, string ackOprName,
  string ackOprNode, string ackOprDomain, string ackOprFullName) → int`
  is the per-alarm full-fidelity native ack.
  `AlarmAckSelected(string ackComment, string ackOprName, string
  ackOprNode, string ackOprDomain, string ackOprFullName) → int`
  acks whatever the selection model currently has selected.
  Several `AckSelected*Group/Tag/Priority/All/Visible*Alarms_Ex(...)`
  variants exist for bulk ack scoped to a group / tag / priority range.
- **Suppress / shelve:** `SupressSelected*` and `ShelveSelected*`
  families plus `DoAlarmShelveAction(...)`. Out of scope for the v1
  alarm path.
- **Snapshot/filter** (`SF*` prefix): `SFSetSortA / SFSetFilterA /
  SFCreateSnapshot / SFGetListCount / SFDeleteSnapshot / SFRefreshAlarm /
  SFGetStatistics`. Snapshot-style query API, distinct from the
  consumer-subscription path. Not currently used.

## What this means

The architecture comment on
`src/MxGateway.Worker/MxAccess/AlarmClientConsumer.cs` (PR A.5) is
**wrong against this deployed assembly**:

> "The AVEVA alarm-manager surface (`IAlarmMgrDataProvider`) exposes
> the events we need as plain .NET events — no Windows message pump
> required."

There is no managed event surface. `AlarmClient.RegisterConsumer`
takes an `hWnd` because **WM_APP messaging is the actual notification
mechanism**: AVEVA's alarm provider WM_APP-pokes the registered window,
and the consumer is expected to call `GetStatistics` on each poke to
pull `ChangeCodes` / `ChangePos` / `hAlarm` arrays, then
`GetAlarmExtendedRec(pos, …)` per index to fetch each changed record.

`AlarmClientConsumer.AlarmRecordReceived` has no production callers as
a result — `RaiseAlarmRecordReceived` is `internal` for tests and
never gets invoked at runtime. Until A.2 lands a WM_APP pump,
`MX_EVENT_FAMILY_ON_ALARM_TRANSITION` cannot carry events.

## Live runtime probe — 2026-05-01

`MxGateway.Worker.Tests.AlarmClientWmProbeTests.ProbeAlarmClientWmMessages`
is a Skip-gated runtime probe that creates a real message-only
window, calls `AlarmClient.RegisterConsumer(hWnd, …)` +
`Subscribe(@"\Galaxy!", …)`, and pumps for 20s while logging every
window message that arrives. Run results below — this turned the
"WM_APP pump" design assumption upside down.

**`RegisterConsumer` and `Subscribe` both returned 0 (success).** The
calls are valid against the deployed assembly; no parameter pinning
needed.

**A registered-message-class WM (ID `0xC275` in this OS session)
fired every ~1s after `Subscribe` completed.** Constant
`wParam = 0x00001100`, constant `lParam = 0x079E46D8` (looks like a
stable pointer into AVEVA-internal state) for all 20 hits. The
constant payload across hits with no Galaxy alarm being fired
suggests this is a **heartbeat/keepalive**, not a per-change
notification.

**Critically: this WM is delivered to AVEVA's own internal window
(`hwnd=0x18032E`) — NOT to the consumer's `hWnd` we passed in.** The
consumer window's `WndProc` received only the standard creation
sequence (`WM_GETMINMAXINFO`, `WM_NCCREATE`, `WM_NCCALCSIZE`,
`WM_CREATE`) and the destruction sequence (`WM_NCDESTROY`,
`WM_DESTROY`, `WM_NCCALCSIZE`) — nothing in between. AVEVA's
notification path runs entirely against AVEVA's internal window;
it never forwards to the user-supplied hWnd.

The message ID itself is dynamic (a `RegisterWindowMessage`
allocation in the >= 0xC000 range), so it cannot be hard-coded —
each consumer process must call `RegisterWindowMessage` with the
correct *string* and use whatever ID the OS returns.

## What this means for A.2

The "WM_APP pump on the user hWnd" design — what the original plan
banner described and what the previous version of this doc
recommended — does not match how AVEVA actually delivers
notifications. The hWnd parameter to `RegisterConsumer` does not
appear to receive any of AVEVA's alarm traffic; it's likely used
only as a registration identity (and perhaps as a parent for modal
dialogs).

Two viable A.2 designs given the probe data:

1. **Polling.** Just call `GetStatistics` on a timer (e.g. every
   500ms in the worker's STA) and react to the change set it
   reports. No window plumbing needed. Trade-off: latency floor =
   poll period; modest CPU floor because the call is cheap. Matches
   the heartbeat-style WM 0xC275 semantics — AVEVA itself runs a
   poll loop internally.
2. **Hook AVEVA's internal window.** Discover AVEVA's own window
   (`hwnd=0x18032E` in the probe), `SetWindowsHookEx` or
   `SetWindowSubclass` on it, and intercept WM 0xC275 on AVEVA's
   thread. Higher fidelity, near-zero latency, but invasive,
   fragile across AVEVA upgrades, and requires running on the same
   process / thread as the AVEVA window. Probably a non-starter
   without further AVEVA documentation.

**Recommendation:** the polling path (option 1) is cheaper to
implement, more robust against AVEVA-internal change, and
acceptable for a typical alarm cadence. The worker's existing STA
already provides a thread-affinitized timer surface. The unanswered
question is whether `GetStatistics` can be safely called outside
AVEVA's own message-pump thread — confirmable by extending the
probe to fire `GetStatistics` on its own thread and check the
result.

## GetStatistics polling — second probe run, 2026-05-01

Extended the probe to call `GetStatistics` every ~2s alongside the
WM logger. Key findings:

- **`GetStatistics` is safely callable from the same thread that
  did `RegisterConsumer` + `Subscribe`.** Every poll returned rc=0
  with no exceptions over 9 polls / 20s window.
- **The deployed Galaxy currently has zero active alarms.** Every
  poll reported `total=0 active=0 suppressed=0 newAlarms=0`. The
  `positions[]` and `handles[]` arrays were empty.
- **`changes=1 codes=[7]` was constant across all polls**, matching
  the constant 1 Hz WM 0xC275 cadence. Code 7 is consistent with a
  "heartbeat / subscription healthy" sentinel — same semantics as
  the WM but reported through the pull-side API.
- `percent=100` (query-complete percentage) was constant — the
  subscription is steady-state.

This confirms the polling design (option 1 in the previous section)
is mechanically viable. The remaining open question is whether
`GetStatistics` populates `positions[] / handles[]` with real
entries when an alarm transition actually fires — proving that
requires firing an alarm.

## Open follow-up probes

Each can be added to `AlarmClientWmProbeTests` as a separate
Skip-gated test:

1. **Fire a real Galaxy alarm during the pump window.** The cleanest
   programmatic trigger is an MxAccess write that flips a
   `$Alarm`-extended boolean to true (alarm in) and back to false
   (alarm out). Pinning the exact tag reference is pending — needs
   either a documented test-fixture tag or an interactive selection
   in System Platform IDE. Once the trigger fires, this resolves
   whether AVEVA's pulled change set arrives via `GetStatistics`
   `positions[] / handles[]` (per-change polling works) or only via
   the AVEVA-internal window (callback path needed).
2. **Hook AVEVA's internal window** to log what WMs it actually
   processes — only relevant if probe 1 shows `GetStatistics` does
   NOT report per-change activity.
3. **Decompile `aaAlarmManagedClient.dll`'s IL** for the
   `RegisterConsumer` method to find what `RegisterWindowMessage`
   string is used and whether there's a callback-registration
   surface on `WNAL_Register` that the managed client wraps. The
   alarmlst.dll strings (`WNAL_CallBack`, "Invalid callbacks" error)
   suggest the underlying C API takes callbacks, but the managed
   wrapper exposes none of them.

PR A.5's `Subscribe` / `AcknowledgeByGuid` / `SnapshotActiveAlarms`
are correct — they're pull-style and don't depend on the
notification mechanism.