docs/AlarmClientDiscovery.md

@@ -87,35 +87,97 @@ 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.
 
-## Implications for A.2
+## Live runtime probe — 2026-05-01
 
-The original plan banner was right: A.2 needs a hidden message-only
-window inside the worker's STA whose hWnd is passed to
-`RegisterConsumer`, with a `WindowProc` that intercepts the AVEVA
-WM_APP message and routes change-enumeration into
-`MxAccessAlarmEventSink.EnqueueTransition`. Open questions before
-implementation:
+`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.
 
-1. **WM_APP message ID.** Not in the public surface — needs either
-   AVEVA's C++ Toolkit reference (canonical doc per `gateway.md`) or
-   a runtime probe (subclass a window, log every WM arriving while a
-   live alarm is fired, identify the AVEVA one). Worth doing once on
-   the dev rig and checking the result in.
-2. **`wParam` / `lParam` semantics.** Probably none — the pattern is
-   "got poked; pull state via `GetStatistics`." Confirm during the
-   probe.
-3. **Threading.** AVEVA almost certainly delivers the WM on the
-   thread that owns the window. The worker's STA is the natural
-   home; the existing `StaRuntime` already runs a pump there. If
-   AVEVA assumes a UI thread (MTA-incompatible call paths inside
-   `GetStatistics`), the alarm path may need its own STA.
-4. **Subscription scope.** `AlarmClient.Subscribe(szSubscription,
-   …)` takes an AVEVA-syntax string for the alarm provider (e.g.
-   `"\Galaxy!"` for a whole Galaxy or `"\Galaxy!Group.Tag"` for a
-   subset). The configured Galaxy name is already known to the
-   worker via the existing data session — reuse it.
+**`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.
+
+## 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.** Confirms
+   whether the WM 0xC275 cadence changes (becomes per-change rather
+   than periodic) and whether `GetStatistics` returns a non-empty
+   `ChangeCodes / ChangePos / hAlarm` triple.
+2. **Call `GetStatistics` on a different thread from the
+   `RegisterConsumer` thread** to test threading affinity.
+3. **Hook AVEVA's internal window** to log what WMs it actually
+   processes (would resolve option 2 above).
+4. **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 missing
-event surface. The event-subscription wiring is what has to be
-replaced.
+are correct — they're pull-style and don't depend on the
+notification mechanism.

src/MxGateway.Worker.Tests/AlarmClientWmProbeTests.cs

@@ -0,0 +1,328 @@
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Threading;
+using AlarmMgrDataProviderCOM;
+using aaAlarmManagedClient;
+using Xunit.Abstractions;
+
+namespace MxGateway.Worker.Tests;
+
+/// <summary>
+///     Runtime probe — registers as an AlarmClient consumer with a real
+///     hidden message-only window, subscribes to a Galaxy alarm provider,
+///     and logs every Win32 message that arrives during a fixed pump
+///     window. The intent is to identify the WM_APP / RegisterWindowMessage
+///     ID that AVEVA's alarm provider posts when alarms change, plus the
+///     <c>wParam</c>/<c>lParam</c> semantics on each.
+///
+///     Skip-gated by default; flip Skip=null and run against the live dev
+///     rig to capture output. Requires:
+///     <list type="bullet">
+///         <item><description>A reachable Galaxy with at least one alarmable object.</description></item>
+///         <item><description>The configured Galaxy expression below to match a real provider (default <c>"\\Galaxy"</c> — adjust if needed).</description></item>
+///         <item><description>An alarm trigger during the pump window (raise / ack / clear something in the Galaxy via System Platform IDE) — without one, only ambient activity is captured.</description></item>
+///     </list>
+/// </summary>
+public sealed class AlarmClientWmProbeTests : IDisposable
+{
+    // Probe configuration. Override in the constructor below if needed.
+    private const string SubscriptionExpression = @"\Galaxy!";
+    private static readonly TimeSpan PumpDuration = TimeSpan.FromSeconds(20);
+
+    [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Unicode, EntryPoint = "CreateWindowExW")]
+    private static extern IntPtr CreateWindowEx(
+        int dwExStyle, string lpClassName, string lpWindowName,
+        int dwStyle, int X, int Y, int nWidth, int nHeight,
+        IntPtr hWndParent, IntPtr hMenu, IntPtr hInstance, IntPtr lpParam);
+
+    [DllImport("user32.dll", SetLastError = true)]
+    [return: MarshalAs(UnmanagedType.Bool)]
+    private static extern bool DestroyWindow(IntPtr hWnd);
+
+    [DllImport("user32.dll", SetLastError = true)]
+    private static extern ushort RegisterClassW(ref WNDCLASSW lpWndClass);
+
+    [DllImport("user32.dll", SetLastError = true)]
+    [return: MarshalAs(UnmanagedType.Bool)]
+    private static extern bool UnregisterClassW(string lpClassName, IntPtr hInstance);
+
+    [DllImport("user32.dll")]
+    private static extern IntPtr DefWindowProcW(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam);
+
+    [DllImport("user32.dll", SetLastError = true)]
+    [return: MarshalAs(UnmanagedType.Bool)]
+    private static extern bool PeekMessage(out MSG lpMsg, IntPtr hWnd, uint wMsgFilterMin, uint wMsgFilterMax, uint wRemoveMsg);
+
+    [DllImport("user32.dll")]
+    private static extern IntPtr DispatchMessage(ref MSG lpMsg);
+
+    [DllImport("user32.dll")]
+    [return: MarshalAs(UnmanagedType.Bool)]
+    private static extern bool TranslateMessage(ref MSG lpMsg);
+
+    [DllImport("kernel32.dll")]
+    private static extern IntPtr GetModuleHandle(string lpModuleName);
+
+    [DllImport("user32.dll", CharSet = CharSet.Unicode)]
+    private static extern uint RegisterWindowMessage(string lpString);
+
+    private const int HWND_MESSAGE = -3;
+    private const uint PM_REMOVE = 0x0001;
+
+    private delegate IntPtr WndProc(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam);
+
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+    private struct WNDCLASSW
+    {
+        public uint style;
+        public IntPtr lpfnWndProc;
+        public int cbClsExtra;
+        public int cbWndExtra;
+        public IntPtr hInstance;
+        public IntPtr hIcon;
+        public IntPtr hCursor;
+        public IntPtr hbrBackground;
+        [MarshalAs(UnmanagedType.LPWStr)] public string? lpszMenuName;
+        [MarshalAs(UnmanagedType.LPWStr)] public string lpszClassName;
+    }
+
+    [StructLayout(LayoutKind.Sequential)]
+    private struct MSG
+    {
+        public IntPtr hwnd;
+        public uint message;
+        public IntPtr wParam;
+        public IntPtr lParam;
+        public uint time;
+        public int x;
+        public int y;
+    }
+
+    private readonly ITestOutputHelper output;
+    private readonly ConcurrentQueue<string> log = new ConcurrentQueue<string>();
+    private readonly Stopwatch elapsed = Stopwatch.StartNew();
+    private GCHandle wndProcHandle;
+    private IntPtr probeWindow = IntPtr.Zero;
+    private string? registeredClass;
+
+    public AlarmClientWmProbeTests(ITestOutputHelper output)
+    {
+        this.output = output;
+    }
+
+    [Fact(Skip = "Runtime probe — flip Skip=null on the dev rig (with live Galaxy) to capture AVEVA WM_APP message IDs")]
+    public void ProbeAlarmClientWmMessages()
+    {
+        // 1. Pre-resolve a few candidate RegisterWindowMessage strings so any
+        //    matches in the captured log can be labeled. None of these is
+        //    confirmed; we record what each resolves to so the actual AVEVA
+        //    message ID (whatever it turns out to be) can be cross-referenced.
+        string[] candidateNames =
+        {
+            "WW_AlarmConsumer", "WW_AlarmManager", "WW_Alarm",
+            "WNAL_AlarmChange", "WNAL_AlarmChanges", "WNAL_AlarmNotify",
+            "WNAL_Notify", "WNAL_ChangeNotification",
+            "AlarmManager.Notify", "AlarmManagerNotify",
+            "ArchestrA.AlarmChange", "AVEVA.AlarmNotify",
+            "aaAlarmManagedClient.Notify",
+            "GotAlarmChanges", "OnAlarmChanges",
+        };
+        foreach (string name in candidateNames)
+        {
+            uint id = RegisterWindowMessage(name);
+            output.WriteLine($"RegisterWindowMessage(\"{name}\") -> 0x{id:X4} ({id})");
+        }
+        output.WriteLine("");
+
+        // 2. Spin up a single STA-affinitized thread, create a hidden message-
+        //    only window owned by it, run RegisterConsumer + Subscribe against
+        //    that window's hWnd, then pump messages on that thread for the
+        //    configured duration. Threading discipline matches the worker's
+        //    StaRuntime model.
+        Exception? threadException = null;
+        var pumpDone = new ManualResetEventSlim(false);
+        var thread = new Thread(() =>
+        {
+            try
+            {
+                RunProbe();
+            }
+            catch (Exception ex)
+            {
+                threadException = ex;
+            }
+            finally
+            {
+                pumpDone.Set();
+            }
+        });
+        thread.IsBackground = false;
+        thread.SetApartmentState(ApartmentState.STA);
+        thread.Start();
+        pumpDone.Wait();
+        thread.Join();
+
+        // 3. Drain the log to xunit output regardless of outcome — partial
+        //    captures are still informative.
+        output.WriteLine("");
+        output.WriteLine($"Captured {log.Count} log line(s):");
+        while (log.TryDequeue(out string? line))
+        {
+            output.WriteLine(line);
+        }
+
+        if (threadException != null)
+        {
+            throw threadException;
+        }
+    }
+
+    private void RunProbe()
+    {
+        // 3a. Register a window class and create a message-only window.
+        WndProc wndProc = ProbeWndProc;
+        wndProcHandle = GCHandle.Alloc(wndProc); // keep delegate alive
+
+        registeredClass = "MxGatewayAlarmProbe_" + Guid.NewGuid().ToString("N");
+        var cls = new WNDCLASSW
+        {
+            style = 0,
+            lpfnWndProc = Marshal.GetFunctionPointerForDelegate(wndProc),
+            hInstance = GetModuleHandle(null!),
+            lpszClassName = registeredClass,
+        };
+        ushort atom = RegisterClassW(ref cls);
+        if (atom == 0)
+        {
+            int err = Marshal.GetLastWin32Error();
+            Log($"RegisterClass failed err=0x{err:X8}");
+            return;
+        }
+        Log($"RegisterClass ok atom=0x{atom:X4} class={registeredClass}");
+
+        probeWindow = CreateWindowEx(
+            dwExStyle: 0, lpClassName: registeredClass, lpWindowName: "AlarmProbe",
+            dwStyle: 0, X: 0, Y: 0, nWidth: 0, nHeight: 0,
+            hWndParent: (IntPtr)HWND_MESSAGE, hMenu: IntPtr.Zero,
+            hInstance: cls.hInstance, lpParam: IntPtr.Zero);
+        if (probeWindow == IntPtr.Zero)
+        {
+            int err = Marshal.GetLastWin32Error();
+            Log($"CreateWindowEx(HWND_MESSAGE) failed err=0x{err:X8}");
+            return;
+        }
+        Log($"Created message-only window hWnd=0x{probeWindow.ToInt64():X}");
+
+        // 3b. Create the AlarmClient and try the lifecycle. RegisterConsumer
+        //    accepts an int hWnd — narrow the IntPtr (sufficient on x86).
+        AlarmClient? client = null;
+        try
+        {
+            client = new AlarmClient();
+            int register = client.RegisterConsumer(
+                hWnd: probeWindow.ToInt32(),
+                szProductName: "AlarmProbe",
+                szApplicationName: "AlarmProbe.Tests",
+                szVersion: "1.0",
+                bRetainHiddenAlarms: false);
+            Log($"RegisterConsumer -> {register}");
+
+            int subscribe = client.Subscribe(
+                szSubscription: SubscriptionExpression,
+                wFromPri: 1, wToPri: 999,
+                QueryType: eQueryType.qtSummary,
+                SortFlags: eSortFlags.sfReturnNewestFirst,
+                FilterMask: eAlarmFilterState.asNone,
+                FilterSpecification: eAlarmFilterState.asNone);
+            Log($"Subscribe('{SubscriptionExpression}') -> {subscribe}");
+
+            // 3c. Pump for the configured duration. Log every message we see
+            //    (filtered light to avoid noise from WM_PAINT / WM_TIMER /
+            //    WM_GETICON spam from typical pumps).
+            DateTime deadline = DateTime.UtcNow + PumpDuration;
+            while (DateTime.UtcNow < deadline)
+            {
+                while (PeekMessage(out MSG msg, IntPtr.Zero, 0, 0, PM_REMOVE))
+                {
+                    LogIfInteresting(msg);
+                    TranslateMessage(ref msg);
+                    DispatchMessage(ref msg);
+                }
+                Thread.Sleep(10);
+            }
+
+            Log($"Pump duration {PumpDuration.TotalSeconds:F0}s elapsed; deregistering.");
+
+            try { int dereg = client.DeregisterConsumer(); Log($"DeregisterConsumer -> {dereg}"); }
+            catch (Exception ex) { Log($"DeregisterConsumer threw: {ex.GetType().Name}: {ex.Message}"); }
+        }
+        finally
+        {
+            try { client?.Dispose(); } catch { /* swallow */ }
+            if (probeWindow != IntPtr.Zero)
+            {
+                DestroyWindow(probeWindow);
+                probeWindow = IntPtr.Zero;
+            }
+            if (registeredClass != null)
+            {
+                UnregisterClassW(registeredClass, GetModuleHandle(null!));
+            }
+        }
+    }
+
+    private void LogIfInteresting(MSG m)
+    {
+        // Filter out the highest-volume noise (timer ticks, paint, mouse moves
+        // from a desktop session). Keep WM_USER..WM_APP+ entirely; those are
+        // the candidates for the AVEVA-registered message.
+        const uint WM_PAINT = 0x000F;
+        const uint WM_TIMER = 0x0113;
+        const uint WM_MOUSEMOVE = 0x0200;
+        const uint WM_NCMOUSEMOVE = 0x00A0;
+        if (m.message == WM_PAINT || m.message == WM_TIMER ||
+            m.message == WM_MOUSEMOVE || m.message == WM_NCMOUSEMOVE)
+        {
+            return;
+        }
+
+        string interpreted = InterpretMessageId(m.message);
+        Log(string.Format(
+            "WM 0x{0:X4} ({1}) wParam=0x{2:X8} lParam=0x{3:X8} hwnd=0x{4:X}",
+            m.message, interpreted,
+            m.wParam.ToInt64() & 0xFFFFFFFF, m.lParam.ToInt64() & 0xFFFFFFFF,
+            m.hwnd.ToInt64()));
+    }
+
+    private static string InterpretMessageId(uint id)
+    {
+        if (id < 0x0400) return "WM_<system>";
+        if (id < 0x8000) return $"WM_USER+0x{id - 0x0400:X4}";
+        if (id < 0xC000) return $"WM_APP+0x{id - 0x8000:X4}";
+        return $"RegisterWindowMessage_0x{id:X4}";
+    }
+
+    private IntPtr ProbeWndProc(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam)
+    {
+        // Log every WM that lands on the probe window itself.
+        string interpreted = InterpretMessageId(msg);
+        Log(string.Format(
+            "WndProc WM 0x{0:X4} ({1}) wParam=0x{2:X8} lParam=0x{3:X8}",
+            msg, interpreted,
+            wParam.ToInt64() & 0xFFFFFFFF, lParam.ToInt64() & 0xFFFFFFFF));
+        return DefWindowProcW(hWnd, msg, wParam, lParam);
+    }
+
+    private void Log(string line)
+    {
+        log.Enqueue($"[t={elapsed.Elapsed.TotalSeconds:F3}s] {line}");
+    }
+
+    public void Dispose()
+    {
+        if (wndProcHandle.IsAllocated) wndProcHandle.Free();
+    }
+}

src/MxGateway.Worker.Tests/MxGateway.Worker.Tests.csproj

@@ -25,4 +25,17 @@
     <ProjectReference Include="..\MxGateway.Worker\MxGateway.Worker.csproj" />
   </ItemGroup>
 
+  <ItemGroup>
+    <Reference Include="aaAlarmManagedClient">
+      <HintPath>C:\Program Files (x86)\ArchestrA\Framework\Bin\ViewAppFramework\Content\MA\aaAlarmManagedClient.dll</HintPath>
+      <Private>true</Private>
+      <SpecificVersion>false</SpecificVersion>
+    </Reference>
+    <Reference Include="IAlarmMgrDataProvider">
+      <HintPath>C:\Program Files (x86)\ArchestrA\Framework\Bin\ViewAppFramework\Content\MA\IAlarmMgrDataProvider.dll</HintPath>
+      <Private>true</Private>
+      <SpecificVersion>false</SpecificVersion>
+    </Reference>
+  </ItemGroup>
+
 </Project>