S4 Tier 0: the bank plays — VST3 marshals MIDI to the S3 core, reads the live bank + resolves WAV the M4 way, mono downmix, lock-free load handoff, LICE sample-pick

src/vst/reaper_bridge.h

@@ -44,8 +44,19 @@ public:
     // Read a "reasampler" ext-state value by key from the host's active project.
     // Returns nullopt when unconnected, when the project can't be resolved, or when the
     // key is absent. This is the S1 read-spike entry point.
+    //
+    // NOT REAL-TIME SAFE (it allocates a read buffer and calls into REAPER): callers on
+    // the audio thread MUST NOT invoke it. The S4 instrument reads on the main/UI thread
+    // and hands a snapshot to the process path (see reasampler_processor.cpp).
     std::optional<std::string> readReasamplerExtState(const std::string& key);
 
+    // The active project's directory (the folder holding its .rpp), forward-slashed,
+    // no trailing slash — the M4 convention persist uses to place the bank alongside
+    // the .rpp. Empty for an unsaved project or when unconnected. The instrument
+    // resolves relative sample paths against this the SAME way persist does
+    // (capture_paths::projectDirOfRpp over EnumProjects(-1)'s .rpp path). Not RT-safe.
+    std::string activeProjectDir();
+
 private:
     // Resolved REAPER API function pointers (by name via getReaperApi). Signatures
     // verified against reaper_plugin_functions.h.
@@ -54,10 +65,15 @@ private:
     using EnumProjExtStateFn = bool (*)(void* proj, const char* extname, int idx,
                                         char* keyOut, int keyOut_sz, char* valOut,
                                         int valOut_sz);
+    // EnumProjects(-1, projfnOut, sz) -> active project + its .rpp path (SDK line
+    // ~1264). The instrument uses idx=-1 (current tab) so it follows the active project,
+    // and reads the .rpp path from the out-buffer exactly as persist.cpp does.
+    using EnumProjectsFn = void* (*)(int idx, char* projfnOut, int projfnOut_sz);
 
     void* hostApp_ = nullptr;  // IReaperHostApplication* (opaque here; used in .cpp)
     GetProjExtStateFn getProjExtState_ = nullptr;
     EnumProjExtStateFn enumProjExtState_ = nullptr;
+    EnumProjectsFn enumProjects_ = nullptr;
 };
 
 }  // namespace reasampler::vst