From a526a6bd789561a526e7311c7a52394fff23a296 Mon Sep 17 00:00:00 2001
From: Levi Burner <leviburner@gmail.com>
Date: Fri, 3 Jun 2022 10:21:08 -0400
Subject: [PATCH] Simulate: move all glfw calls to main thread to fix MacOS

---
 simulate/main.cc     | 59 +++++++++++++++++++++++++-------------------
 simulate/simulate.cc | 20 +--------------
 simulate/simulate.h  | 10 +++-----
 3 files changed, 39 insertions(+), 50 deletions(-)

diff --git a/simulate/main.cc b/simulate/main.cc
index 34e8f263..b5496367 100644
--- a/simulate/main.cc
+++ b/simulate/main.cc
@@ -92,7 +92,7 @@ mjModel* LoadModel(const char* file, mj::Simulate& simulate) {
 }
 
 // simulate in background thread (while rendering in main thread)
-void SimulateLoop(mj::Simulate& simulate) {
+void PhysicsLoop(mj::Simulate& simulate) {
   // cpu-sim syncronization point
   double cpusync = 0;
   mjtNum simsync = 0;
@@ -222,6 +222,31 @@ void SimulateLoop(mj::Simulate& simulate) {
 }
 } // end unnamed namespace
 
+//---------------------------------- physics_thread ---------------------------------------
+void PhysicsThread(mj::Simulate* simulate, const char* filename) {
+  // request loadmodel if file given (otherwise drag-and-drop)
+  if (filename != nullptr) {
+    m = LoadModel(filename, *simulate);
+    if (m) {
+      d = mj_makeData(m);
+      simulate->load(filename, m, d, true);
+      mj_forward(m, d);
+
+      // allocate ctrlnoise
+      free(ctrlnoise);
+      ctrlnoise = (mjtNum*) malloc(sizeof(mjtNum)*m->nu);
+      mju_zero(ctrlnoise, m->nu);
+    }
+  }
+
+  PhysicsLoop(*simulate);
+
+  // delete everything we allocated
+  free(ctrlnoise);
+  mj_deleteData(d);
+  mj_deleteModel(m);
+}
+
 //---------------------------------- main -------------------------------------------------
 
 // run event loop
@@ -240,33 +265,17 @@ int main(int argc, const char** argv) {
     mju_error("could not initialize GLFW");
   }
 
-  // start simulation thread (this creates the UI)
-  simulate.startthread();
-
-  // request loadmodel if file given (otherwise drag-and-drop)
-  if (argc>1) {
-    m = LoadModel(argv[1], simulate);
-    if (m) {
-      d = mj_makeData(m);
-      simulate.load(argv[1], m, d, true);
-      mj_forward(m, d);
-
-      // allocate ctrlnoise
-      free(ctrlnoise);
-      ctrlnoise = (mjtNum*) malloc(sizeof(mjtNum)*m->nu);
-      mju_zero(ctrlnoise, m->nu);
-    }
+  const char* filename = nullptr;
+  if (argc >  1) {
+    filename = argv[1];
   }
 
-  SimulateLoop(simulate);
+  // start physics thread
+  std::thread physicsthreadhandle = std::thread(&PhysicsThread, &simulate, filename);
 
-  // If simulate loop exited its time to stop the UI
-  simulate.stopthread();
-
-  // delete everything we allocated
-  free(ctrlnoise);
-  mj_deleteData(d);
-  mj_deleteModel(m);
+  // start simulation UI loop (blocking call)
+  simulate.renderloop();
+  physicsthreadhandle.join();
 
   // terminate GLFW (crashes with Linux NVidia drivers)
 #if defined(__APPLE__) || defined(_WIN32)
diff --git a/simulate/simulate.cc b/simulate/simulate.cc
index 78eb1225..0033f788 100644
--- a/simulate/simulate.cc
+++ b/simulate/simulate.cc
@@ -1535,18 +1535,6 @@ namespace mju = ::mujoco::sample_util;
 Simulate::Simulate(void) {
 } // TODO constructor is now empty...
 
-//------------------------ start the render thread -----------------------------
-void Simulate::startthread(void) {
-  this->renderthreadhandle = std::thread(&Simulate::renderthread, this);
-}
-
-//------------------------ stop the render thread ------------------------------
-void Simulate::stopthread(void) {
-    // stop simulation thread
-  this->exitrequest = 1;
-  this->renderthreadhandle.join();
-}
-
 //------------------------ apply pose perturbations ----------------------------
 void Simulate::applyposepertubations(int flg_paused) {
   if (this->m != nullptr) {
@@ -1798,7 +1786,7 @@ void Simulate::clearcallback(void) {
   uiClearCallback(this->window);
 }
 
-void Simulate::renderthread(void) {
+void Simulate::renderloop(void) {
   // Set timer callback (milliseconds)
   mjcb_time = timer;
 
@@ -1900,12 +1888,6 @@ void Simulate::renderthread(void) {
   this->clearcallback();
   mjv_freeScene(&this->scn);
   mjr_freeContext(&this->con);
-
-  // terminate GLFW (crashes with Linux NVidia drivers)
-  // Must call terminate in this thread on Windows with NVidia drivers (Intel is fine)
-#if defined(__APPLE__) || defined(_WIN32)
-  glfwTerminate();
-#endif
 }
 
 }  // namespace mujoco
diff --git a/simulate/simulate.h b/simulate/simulate.h
index 461318c6..f6da9c10 100644
--- a/simulate/simulate.h
+++ b/simulate/simulate.h
@@ -44,7 +44,7 @@ class MJSIMULATEAPI Simulate {
   Simulate(void);
 
   // Start the Simulate UI thread
-  void startthread(void);
+  // void startthread(void);
 
   // Stop the Simulate UI thread
   void stopthread(void);
@@ -72,15 +72,13 @@ class MJSIMULATEAPI Simulate {
   // clear callbacks registered in external structures
   void clearcallback(void);
 
-  // thread to render the UI
-  void renderthread(void);
+  // loop to render the UI (must be called from main thread because of MacOS)
+  // https://discourse.glfw.org/t/multithreading-glfw/573/5
+  void renderloop(void);
 
   // constants
   static constexpr int kMaxFilenameLength = 1000;
 
-  // the UI rendering thread
-  std::thread renderthreadhandle;
-
   // model and data to be visualized
   mjModel* mnew = nullptr;
   mjData* dnew = nullptr;