fix(instrument_drop): narrow FX hotspot to tcp.fx/mcp.fx, not bare tcp/mcp (S-VIEW-BUG-1)

tests/test_instrument_drop.cpp

@@ -109,23 +109,25 @@ static void testBase64DecodeRejectsMalformed() {
 //
 // THE BUG: dropping a capture onto a track's FX button (in the TCP) never armed the
 // instrument drop, because the old predicate matched only "fx_" — which the SDK reserves for
-// the FX CHAIN / FLOATING-FX windows. A track-panel hit (where the FX button lives) reports a
-// string beginning with "tcp"/"mcp". These tests fix the classifier at the boundary the shell
-// consumes: each would FAIL under the old "fx_"-only rule for the tcp/mcp cases.
+// the FX CHAIN / FLOATING-FX windows. A track-panel FX-button hit reports "tcp.fx"/"mcp.fx"
+// (SDK §GetThingFromPoint: "string will begin with 'tcp' or 'mcp' or 'tcp.mute' etc").
+//
+// THE FIX: narrow to two documented FX-bearing surfaces:
+//   * "tcp.fx" / "mcp.fx"  — the TCP/MCP FX button (exact token, NOT bare tcp/mcp)
+//   * "fx_*"               — the FX-chain / floating-FX windows (prefix, as before)
+// Bare "tcp"/"mcp" and any other "tcp.*"/"mcp.*" sub-element (e.g. "tcp.mute", "tcp.vol")
+// are non-FX track-panel regions — an instrument drop must NOT fire there.
 
-// The regression case: the TCP FX-button surface reports "tcp*" and MUST classify as an FX
-// hotspot. Under the pre-fix "fx_"-only predicate these all returned false — the exact miss
-// that produced the "drops as audio to arrange" symptom.
-static void testTcpMcpPanelIsHotspot() {
-    CHECK(infoNamesFxHotspot("tcp"));       // bare track control panel
-    CHECK(infoNamesFxHotspot("tcp.fx"));    // the TCP FX-button WALTER element
-    CHECK(infoNamesFxHotspot("tcp.mute"));  // any tcp.* sub-element resolves to the track
-    CHECK(infoNamesFxHotspot("mcp"));       // mixer control panel
-    CHECK(infoNamesFxHotspot("mcp.fx"));    // the MCP FX area
+// The TCP/MCP FX button specifically — the surface that arms an instrument drop (S-VIEW-BUG-1
+// fix). Under the old "fx_"-only predicate these returned false — the exact miss that produced
+// the "drops as audio to arrange" symptom on the FX button.
+static void testTcpMcpFxButtonIsHotspot() {
+    CHECK(infoNamesFxHotspot("tcp.fx"));    // TCP FX button (SDK token)
+    CHECK(infoNamesFxHotspot("mcp.fx"));    // MCP FX area (SDK token)
 }
 
 // The FX chain / floating-FX windows (the surfaces the ORIGINAL predicate matched) still
-// classify as hotspots — the fix widens the rule, it does not regress the "fx_" surface.
+// classify as hotspots — the fix does not regress the "fx_" surface.
 static void testFxWindowStillHotspot() {
     CHECK(infoNamesFxHotspot("fx_chain"));  // FX chain window
     CHECK(infoNamesFxHotspot("fx_0"));      // first FX, floating
@@ -133,9 +135,13 @@ static void testFxWindowStillHotspot() {
 }
 
 // Non-FX surfaces are NOT hotspots — a drop here is not an instrument drop (it would fall
-// through to the OS drag / no-op). Guards against over-broad matching (e.g. "spacer_0" must
-// not match despite living near the tracks; "arrange" is the audio-import surface).
+// through to the OS drag / no-op). This includes the bare TCP/MCP tokens and all non-FX
+// "tcp.*"/"mcp.*" sub-elements (e.g. mute button, volume fader, track name, meter).
 static void testNonFxSurfacesAreNotHotspot() {
+    CHECK(!infoNamesFxHotspot("tcp"));       // bare track control panel — NOT an FX hotspot
+    CHECK(!infoNamesFxHotspot("mcp"));       // bare mixer control panel — NOT an FX hotspot
+    CHECK(!infoNamesFxHotspot("tcp.mute"));  // mute button — track panel, not FX
+    CHECK(!infoNamesFxHotspot("tcp.vol"));   // volume fader — track panel, not FX
     CHECK(!infoNamesFxHotspot("arrange"));
     CHECK(!infoNamesFxHotspot("spacer_0"));
     CHECK(!infoNamesFxHotspot(""));          // pointer over nothing REAPER classifies
@@ -152,7 +158,7 @@ int main() {
     testBase64RoundTripAllBytes();
     testBase64DecodeRejectsMalformed();
 
-    testTcpMcpPanelIsHotspot();
+    testTcpMcpFxButtonIsHotspot();
     testFxWindowStillHotspot();
     testNonFxSurfacesAreNotHotspot();