Workaround for broken VSync in Simulate on macOS.

OpenGL VSync became broken again in macOS 13 (https://github.com/glfw/glfw/issues/2249). This workaround is similar to https://github.com/glfw/glfw/pull/2277 but is implemented entirely outside of GLFW.

PiperOrigin-RevId: 516320722
Change-Id: Ib8a651a942f592c74e00ad3c7b22f2dfd156be5f

simulate/glfw_corevideo.h

@@ -0,0 +1,56 @@
+// Copyright 2023 DeepMind Technologies Limited
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef MUJOCO_SIMULATE_GLFW_COREVIDEO_H_
+#define MUJOCO_SIMULATE_GLFW_COREVIDEO_H_
+
+#ifndef __APPLE__
+#error "This header only works on macOS."
+#endif
+
+#include <condition_variable>
+#include <mutex>
+
+#include "glfw_dispatch.h"
+
+#ifdef __OBJC__
+#import <CoreVideo/CoreVideo.h>
+#else
+typedef void* CVDisplayLinkRef;
+#endif
+
+// Workaround for perpertually broken OpenGL VSync on macOS,
+// most recently https://github.com/glfw/glfw/issues/2249.
+namespace mujoco {
+class GlfwCoreVideo {
+ public:
+  GlfwCoreVideo(GLFWwindow* window);
+  ~GlfwCoreVideo();
+  void EnqueueSwap();
+  void WaitForSwap();
+  int DisplayLinkCallback();
+  void UpdateDisplayLink();
+
+ private:
+  GLFWwindow* window_;
+  CVDisplayLinkRef display_link_;
+
+  bool second_buffer_has_content_;
+  std::mutex mu_;
+  std::condition_variable cond_;
+};
+}  // namespace mujoco
+
+
+#endif  // MUJOCO_SIMULATE_GLFW_COREVIDEO_H_