From 0a63256b651a8a27650ef1701948698897a7634c Mon Sep 17 00:00:00 2001
From: Jean Pierre Cimalando <jp-dev@inbox.ru>
Date: Thu, 18 Mar 2021 02:17:06 +0100
Subject: [PATCH] Background work when idle

---
 plugins/vst/SfizzVstProcessor.cpp | 75 +++++++++++++++++--------------
 plugins/vst/SfizzVstProcessor.h   |  5 +--
 2 files changed, 43 insertions(+), 37 deletions(-)

diff --git a/plugins/vst/SfizzVstProcessor.cpp b/plugins/vst/SfizzVstProcessor.cpp
index 93519ee6..711aa049 100644
--- a/plugins/vst/SfizzVstProcessor.cpp
+++ b/plugins/vst/SfizzVstProcessor.cpp
@@ -37,7 +37,6 @@ static const char* kRingIdOsc = "Osc";
 static const char* kMsgIdSetNumVoices = "SetNumVoices";
 static const char* kMsgIdSetOversampling = "SetOversampling";
 static const char* kMsgIdSetPreloadSize = "SetPreloadSize";
-static const char* kMsgIdCheckShouldReload = "CheckShouldReload";
 static const char* kMsgIdNotifyPlayState = "NotifyPlayState";
 static const char* kMsgIdReceiveMessage = "ReceiveMessage";
 static const char* kMsgIdNoteEvents = "NoteEvents";
@@ -204,7 +203,6 @@ tresult PLUGIN_API SfizzVstProcessor::setActive(TBool state)
         synth->setSampleRate(processSetup.sampleRate);
         synth->setSamplesPerBlock(processSetup.maxSamplesPerBlock);
 
-        _fileChangePeriod = static_cast<uint32>(1.0 * processSetup.sampleRate);
         _playStateChangePeriod = static_cast<uint32>(50e-3 * processSetup.sampleRate);
 
         startBackgroundWork();
@@ -271,13 +269,6 @@ tresult PLUGIN_API SfizzVstProcessor::process(Vst::ProcessData& data)
 
     synth.renderBlock(outputs, numFrames, numChannels);
 
-    _fileChangeCounter += numFrames;
-    if (_fileChangeCounter > _fileChangePeriod) {
-        _fileChangeCounter %= _fileChangePeriod;
-        if (writeWorkerMessage(kMsgIdCheckShouldReload, nullptr, 0))
-            _semaToWorker.post();
-    }
-
     _playStateChangeCounter += numFrames;
     if (_playStateChangeCounter > _playStateChangePeriod) {
         _playStateChangeCounter %= _playStateChangePeriod;
@@ -640,19 +631,28 @@ void SfizzVstProcessor::loadSfzFileOrDefault(sfz::Sfizz& synth, const std::strin
 
 void SfizzVstProcessor::doBackgroundWork()
 {
+    using Clock = std::chrono::steady_clock;
+
+    bool haveDoneIdleWork = false;
+    Clock::time_point lastIdleWorkTime;
+
     for (;;) {
-        _semaToWorker.wait();
+        bool isNotified = _semaToWorker.timed_wait(1000);
 
         if (!_workRunning)
             break;
 
-        RTMessagePtr msg = readWorkerMessage();
-        if (!msg) {
-            fprintf(stderr, "[Sfizz] message synchronization error in worker\n");
-            std::abort();
-        }
+        const char* id = nullptr;
+        RTMessagePtr msg;
 
-        const char* id = msg->type;
+        if (isNotified) {
+            msg = readWorkerMessage();
+            if (!msg) {
+                fprintf(stderr, "[Sfizz] message synchronization error in worker\n");
+                std::abort();
+            }
+            id = msg->type;
+        }
 
         if (id == kMsgIdSetNumVoices) {
             int32 value = *msg->payload<int32>();
@@ -669,23 +669,6 @@ void SfizzVstProcessor::doBackgroundWork()
             std::lock_guard<SpinMutex> lock(_processMutex);
             _synth->setPreloadSize(value);
         }
-        else if (id == kMsgIdCheckShouldReload) {
-            if (_synth->shouldReloadFile()) {
-                fprintf(stderr, "[Sfizz] sfz file has changed, reloading\n");
-                std::lock_guard<SpinMutex> lock(_processMutex);
-                loadSfzFileOrDefault(*_synth, _state.sfzFile);
-
-                Steinberg::OPtr<Vst::IMessage> reply { allocateMessage() };
-                reply->setMessageID("LoadedSfz");
-                reply->getAttributes()->setBinary("File", _state.sfzFile.data(), _state.sfzFile.size());
-                sendMessage(reply);
-            }
-            else if (_synth->shouldReloadScala()) {
-                fprintf(stderr, "[Sfizz] scala file has changed, reloading\n");
-                std::lock_guard<SpinMutex> lock(_processMutex);
-                _synth->loadScalaFile(_state.scalaFile);
-            }
-        }
         else if (id == kMsgIdNotifyPlayState) {
             SfizzPlayState playState = *msg->payload<SfizzPlayState>();
             Steinberg::OPtr<Vst::IMessage> notification { allocateMessage() };
@@ -705,6 +688,32 @@ void SfizzVstProcessor::doBackgroundWork()
             notification->getAttributes()->setBinary("Events", msg->payload<uint8_t>(), msg->size);
             sendMessage(notification);
         }
+
+        Clock::time_point currentTime = Clock::now();
+        if (!haveDoneIdleWork || currentTime - lastIdleWorkTime > std::chrono::seconds(1)) {
+            doBackgroundIdle();
+            haveDoneIdleWork = true;
+            lastIdleWorkTime = currentTime;
+        }
+    }
+}
+
+void SfizzVstProcessor::doBackgroundIdle()
+{
+    if (_synth->shouldReloadFile()) {
+        fprintf(stderr, "[Sfizz] sfz file has changed, reloading\n");
+        std::lock_guard<SpinMutex> lock(_processMutex);
+        loadSfzFileOrDefault(*_synth, _state.sfzFile);
+
+        Steinberg::OPtr<Vst::IMessage> reply { allocateMessage() };
+        reply->setMessageID("LoadedSfz");
+        reply->getAttributes()->setBinary("File", _state.sfzFile.data(), _state.sfzFile.size());
+        sendMessage(reply);
+    }
+    if (_synth->shouldReloadScala()) {
+        fprintf(stderr, "[Sfizz] scala file has changed, reloading\n");
+        std::lock_guard<SpinMutex> lock(_processMutex);
+        _synth->loadScalaFile(_state.scalaFile);
     }
 }
 
diff --git a/plugins/vst/SfizzVstProcessor.h b/plugins/vst/SfizzVstProcessor.h
index 2219ab6a..f34e1b4d 100644
--- a/plugins/vst/SfizzVstProcessor.h
+++ b/plugins/vst/SfizzVstProcessor.h
@@ -72,10 +72,6 @@ private:
     Ring_Buffer _fifoMessageFromUi;
     SpinMutex _processMutex;
 
-    // file modification periodic checker
-    uint32 _fileChangeCounter = 0;
-    uint32 _fileChangePeriod = 0;
-
     // state notification periodic timer
     uint32 _playStateChangeCounter = 0;
     uint32 _playStateChangePeriod = 0;
@@ -99,6 +95,7 @@ private:
 
     // worker
     void doBackgroundWork();
+    void doBackgroundIdle();
     void startBackgroundWork();
     void stopBackgroundWork();
     // writer