fix occasional mac editor crash when play/stop the game multiple times

engine/src/shell/platform/unity/darwin/ios/unity_surface_manager.h

   UnitySurfaceManager(IUnityInterfaces* unity_interfaces);
   ~UnitySurfaceManager();
 
+  //openGLES contexts
+  static EAGLContext *gl_context_;
+  static EAGLContext *gl_resource_context_;
+
   void* CreateRenderTexture(size_t width, size_t height);
 
   void ReleaseNativeRenderContext();
   CVPixelBufferRef pixelbuffer_ref = nullptr;
 
   //gl handlers
-  EAGLContext *gl_context_ = NULL;
-  EAGLContext *gl_resource_context_ = NULL;
   GLuint default_fbo_ = 0;
   GLuint gl_tex_ = 0;
   CVOpenGLESTextureCacheRef gl_tex_cache_ref_ = nullptr;

engine/src/shell/platform/unity/darwin/ios/unity_surface_manager.mm

 #define GL_UNSIGNED_INT_8_8_8_8_REV 0x8367
 
 namespace uiwidgets {
+
+EAGLContext* UnitySurfaceManager::gl_context_ = nullptr;
+EAGLContext* UnitySurfaceManager::gl_resource_context_ = nullptr;
+
 UnitySurfaceManager::UnitySurfaceManager(IUnityInterfaces* unity_interfaces)
 {
   FML_DCHECK(metal_device_ == nullptr);
   metal_device_ = metalGraphics->MetalDevice();
 
   //create opengl context
-  FML_DCHECK(!gl_context_);
-  FML_DCHECK(!gl_resource_context_);
+  if (gl_context_ == nullptr && gl_resource_context_ == nullptr) {
+    gl_context_ = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
+    gl_resource_context_ = [[EAGLContext alloc] initWithAPI:[gl_context_ API] sharegroup: [gl_context_ sharegroup]];
+  }
-  gl_context_ = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
-  gl_resource_context_ = [[EAGLContext alloc] initWithAPI:[gl_context_ API] sharegroup: [gl_context_ sharegroup]];
   FML_DCHECK(gl_context_ != nullptr && gl_resource_context_ != nullptr);
 }
 
 void UnitySurfaceManager::ReleaseNativeRenderContext()
 {
   FML_DCHECK(gl_resource_context_);
-  gl_resource_context_ = nullptr;
-  gl_context_ = nullptr;
 
   [EAGLContext setCurrentContext:nil];
 

engine/src/shell/platform/unity/darwin/macos/unity_surface_manager.h

   UnitySurfaceManager(IUnityInterfaces* unity_interfaces);
   ~UnitySurfaceManager();
 
+  //openGL contexts
+  static NSOpenGLContext *gl_context_;
+  static NSOpenGLContext *gl_resource_context_;
+
   void* CreateRenderTexture(size_t width, size_t height);
 
   void ReleaseNativeRenderContext();
   //pixel buffer handles
   CVPixelBufferRef pixelbuffer_ref = nullptr;
   //openGL handlers
-  NSOpenGLContext *gl_context_ = NULL;
-  NSOpenGLContext *gl_resource_context_ = NULL;
   GLuint default_fbo_ = 0;
   GLuint gl_tex_ = 0;
   CVOpenGLTextureCacheRef gl_tex_cache_ref_ = nullptr;

engine/src/shell/platform/unity/darwin/macos/unity_surface_manager.mm

 #include "Unity/IUnityGraphicsMetal.h"
 
 namespace uiwidgets {
+
+NSOpenGLContext* UnitySurfaceManager::gl_context_ = nullptr;
+NSOpenGLContext* UnitySurfaceManager::gl_resource_context_ = nullptr;
+
 UnitySurfaceManager::UnitySurfaceManager(IUnityInterfaces* unity_interfaces)
 {
   FML_DCHECK(metal_device_ == nullptr);
   metal_device_ = metalGraphics->MetalDevice();
 
   //create opengl context
-  FML_DCHECK(!gl_context_);
-  FML_DCHECK(!gl_resource_context_);
-
-  NSOpenGLPixelFormatAttribute attrs[] =
+  if (gl_context_ == nullptr && gl_resource_context_ == nullptr) {
+    NSOpenGLPixelFormatAttribute attrs[] =
-  NSOpenGLPixelFormat *pixelFormat = [[NSOpenGLPixelFormat alloc] initWithAttributes:attrs];
+    NSOpenGLPixelFormat *pixelFormat = [[NSOpenGLPixelFormat alloc] initWithAttributes:attrs];
-  //gl_context_ may be created unproperly, we can check this using the relevant gl_resource_context_
-  //loop until the created gl_context_ is ok, otherwise the program will crash anyway
-  while(gl_resource_context_ == nil) {
-    gl_context_ = [[NSOpenGLContext alloc] initWithFormat:pixelFormat shareContext:nil];
-    gl_resource_context_ = [[NSOpenGLContext alloc] initWithFormat:pixelFormat shareContext:gl_context_];  
+    //gl_context_ may be created unproperly, we can check this using the relevant gl_resource_context_
+    //loop until the created gl_context_ is ok, otherwise the program will crash anyway
+    while(gl_resource_context_ == nil) {
+      gl_context_ = [[NSOpenGLContext alloc] initWithFormat:pixelFormat shareContext:nil];
+      gl_resource_context_ = [[NSOpenGLContext alloc] initWithFormat:pixelFormat shareContext:gl_context_];  
-    if (gl_resource_context_ == nil) {
+      if (gl_resource_context_ == nil) {
+      }
     }
   }
 
 void UnitySurfaceManager::ReleaseNativeRenderContext()
 {
   FML_DCHECK(gl_resource_context_);
-  CGLReleaseContext(gl_resource_context_.CGLContextObj);
-  gl_resource_context_ = nullptr;
-  CGLReleaseContext(gl_context_.CGLContextObj);
-  gl_context_ = nullptr;
 
   FML_DCHECK(metal_device_ != nullptr);
   metal_device_ = nullptr;