Fix GLFW crash when Python exits while the passive viewer is running.

Fixes #790

PiperOrigin-RevId: 549440435
Change-Id: I808f6aaab6662225e5fe1131e0da72eca6011ba9

simulate/glfw_adapter.cc

@@ -110,6 +110,7 @@ GlfwAdapter::GlfwAdapter() {
 }
 
 GlfwAdapter::~GlfwAdapter() {
+  FreeMjrContext();
   Glfw().glfwMakeContextCurrent(nullptr);
   Glfw().glfwDestroyWindow(window_);
 }

simulate/platform_ui_adapter.cc

@@ -21,7 +21,7 @@ PlatformUIAdapter::PlatformUIAdapter() {
   mjr_defaultContext(&con_);
 }
 
-PlatformUIAdapter::~PlatformUIAdapter() {
+void PlatformUIAdapter::FreeMjrContext() {
   mjr_freeContext(&con_);
 }
 

simulate/platform_ui_adapter.h

@@ -22,7 +22,7 @@
 namespace mujoco {
 class PlatformUIAdapter {
  public:
-  virtual ~PlatformUIAdapter();
+  virtual ~PlatformUIAdapter() = default;
 
   inline mjuiState& state() { return state_; }
   inline const mjuiState& state() const { return state_; }
@@ -38,7 +38,7 @@ class PlatformUIAdapter {
     layout_callback_ = layout_callback;
   }
 
-  // Optionally overrideable function to (re)create an mjrContext for an mjModel
+  // Optionally overridable function to (re)create an mjrContext for an mjModel
   virtual bool RefreshMjrContext(const mjModel* m, int fontscale);
 
   virtual bool EnsureContextSize();
@@ -73,6 +73,7 @@ class PlatformUIAdapter {
 
  protected:
   PlatformUIAdapter();
+  void FreeMjrContext();
 
   // Event handlers
   void OnFilesDrop(int count, const char** paths);