Guard the FX-drain busy indicator against silent enum drift and cursor edge cases

Promote drainStateNow's switch to error-on-missing-case locally; set DWLP_MSGRESULT on WM_SETCURSOR; add an HTCLIENT guard; skip refreshBusyCursor during a live drag; mark the docked-dialog WM_SETCURSOR routing premise [verify - DAW].

src/shell/panel/CLAUDE.md

@@ -73,7 +73,8 @@ live in `shell/bank_ops`, a sibling directory, not here.
   REAPER's, and the SDK exposes nothing host-wide. A global `SetSystemCursor` or a message
   hook would reach further and is rejected — do not reintroduce either. `IDC_APPSTARTING`
   is Windows-only (SWELL ships no equivalent), so on mac/Linux the readout is the whole
-  indicator.
+  indicator. `[verify — DAW]` whether REAPER's docker even routes `WM_SETCURSOR` to the
+  docked child dialog at all — the whole Windows half of this rests on that.
 - **No hit-test geometry in untestable shell code.** Even when reusing a WDL piece
   (e.g. a `vwnd` control for a long scroll list), layout/hit-test math stays in pure
   CTest-covered modules — do not import a WDL control's retained-mode object model

src/shell/panel/panel_input.cpp

@@ -479,6 +479,19 @@ bool g_accelRegistered = false;
 
 // The ONE map from the reclaimer's answer to the pure readout's vocabulary. Name-for-name
 // so a divergence reads as one; the decision itself is entirely fxReclaimActivity's.
+// This TU compiles straight into the reaper_reasampler MODULE, which carries none of
+// reasampler_pure_library's -Werror=switch/we4062 promotion (footer_bar's mirror switch
+// over FxDrainState has that; this one didn't) — a fourth FxReclaimActivity enumerator
+// would fall through to Idle here with no diagnostic at all. Promoted locally instead of
+// widening the target-wide flag, which would need auditing every switch already compiled
+// into this MODULE for an intentionally-partial case list.
+#if defined(_MSC_VER)
+#pragma warning(push)
+#pragma warning(error : 4062)
+#elif defined(__GNUC__) || defined(__clang__)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic error "-Wswitch"
+#endif
 FxDrainState drainStateNow() {
     switch (fxReclaimActivity()) {
         case FxReclaimActivity::Online:  return FxDrainState::Online;
@@ -487,6 +500,11 @@ FxDrainState drainStateNow() {
     }
     return FxDrainState::Idle;
 }
+#if defined(_MSC_VER)
+#pragma warning(pop)
+#elif defined(__GNUC__) || defined(__clang__)
+#pragma GCC diagnostic pop
+#endif
 
 }  // namespace
 

src/shell/panel/panel_window.cpp

@@ -100,7 +100,9 @@ void handleDropFiles(HDROP hDrop) {
 // cursor at all and the footer readout carries the state alone. The cursor reaches OUR
 // windows only; REAPER's arrange and mixer answer their own WM_SETCURSOR and the SDK
 // exposes nothing host-wide to ask for. A global SetSystemCursor or a message hook would
-// reach further and is deliberately not done.
+// reach further and is deliberately not done. [verify — DAW] whether REAPER's docker even
+// routes WM_SETCURSOR to the docked child dialog at all — the premise the whole Windows
+// half of this feature rests on.
 #ifdef _WIN32
 HCURSOR busyCursor() { return LoadCursor(nullptr, IDC_APPSTARTING); }
 #else
@@ -118,12 +120,24 @@ bool busyCursorApplies() {
 WDL_DLGRET dlgProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
     switch (msg) {
         case WM_SETCURSOR:
+            // Non-client hits (resize border, etc.) are not ours to answer for; let the
+            // default handling run. Harmless today (IDD_BANK_PANEL is a bare WS_CHILD
+            // with no controls or border) but the guard is the conventional one.
+            if (LOWORD(lParam) != HTCLIENT) return 0;
             // Claiming the message (non-zero) is what stops the default arrow from being
             // reapplied underneath us — on Win32 via DefDlgProc, on SWELL via the same
             // return test in swell-wnd-generic.cpp. Falling through leaves every other
             // cursor decision exactly where it was (panel_drag's per-move SetCursor).
             if (busyCursorApplies()) {
                 SetCursor(busyCursor());
+                // A DLGPROC conveys its result through DWLP_MSGRESULT, not the raw
+                // return value; WM_SETCURSOR is not on the exception-message list that
+                // skips this. Without it the bare `return 1` still suppresses
+                // DefDlgProc's own cursor (SWELL checks the raw return too), but a
+                // parent or sender reading the result would see "unhandled".
+#ifdef _WIN32
+                SetWindowLongPtr(hwnd, DWLP_MSGRESULT, TRUE);
+#endif
                 return 1;
             }
             return 0;
@@ -240,7 +254,10 @@ void closePanel() {
 }  // namespace
 
 void refreshBusyCursor() {
-    if (!g_panel.hwnd) return;
+    // Nothing to refresh on mac/Linux (busyCursor() is always null there), and a live
+    // drag owns the cursor already (panel_drag::applyDragCursor) — forcing IDC_ARROW
+    // here on a drain edge mid-drag would stomp that cue until the next mouse move.
+    if (!g_panel.hwnd || !busyCursor() || g_panel.dragArmed || g_panel.dragging) return;
     POINT pt{};
     GetCursorPos(&pt);  // SWELL's returns void, so its result is deliberately not tested
     // Only when our own window is the one under the pointer: a menu or another window