Add OSX and WIN32 support for getting the native window pointer.

PiperOrigin-RevId: 838720433
Change-Id: Id7123bcf456d0c2d32e67b204564fe8c495004cd

src/experimental/platform/CMakeLists.txt

@@ -39,6 +39,15 @@ target_sources(${MUJOCO_PLATFORM_TARGET_NAME}
         window.cc
         window.h
 )
+
+if(APPLE)
+    set_source_files_properties(window_osx.mm PROPERTIES
+        COMPILE_FLAGS "-x objective-c++")
+    target_sources(${MUJOCO_PLATFORM_TARGET_NAME} PUBLIC
+        window_osx.mm
+    )
+endif()
+
 target_include_directories(${MUJOCO_PLATFORM_TARGET_NAME}
     PUBLIC
         ${PROJECT_SOURCE_DIR}/include

src/experimental/platform/window.cc

@@ -34,6 +34,10 @@
 #undef Status
 #endif
 
+#if defined(__APPLE__)
+extern void* GetNativeWindowOsx(void* window);
+#endif
+
 namespace mujoco::platform {
 
 static void InitImGui(SDL_Window* window, const LoadAssetFn& load_asset_fn,
@@ -117,11 +121,17 @@ Window::Window(std::string_view title, int width, int height, Config config,
     SDL_GL_MakeCurrent(sdl_window_, gl_context);
   }
 
-  #ifdef __linux__
-    SDL_SysWMinfo wmi;
-    SDL_VERSION(&wmi.version);
-    SDL_GetWindowWMInfo(sdl_window_, &wmi);
+  SDL_SysWMinfo wmi;
+  SDL_VERSION(&wmi.version);
+  SDL_GetWindowWMInfo(sdl_window_, &wmi);
+
+  #if defined(__linux__)
     native_window_ = reinterpret_cast<void*>(wmi.info.x11.window);
+  #elif defined(__WIN32__)
+    native_window_ = reinterpret_cast<void*>(wmi.info.win.window);
+  #elif defined(__APPLE__)
+    native_window_ =
+        GetNativeWindowOsx(reinterpret_cast<void*>(wmi.info.cocoa.window));
   #endif
 }
 

src/experimental/platform/window_osx.mm

@@ -0,0 +1,22 @@
+// Copyright 2025 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.
+
+#import <AppKit/NSWindow.h>
+#import <AppKit/NSView.h>
+
+void* GetNativeWindowOsx(void* window) {
+  NSWindow* ns_window = (__bridge NSWindow*)window;
+  NSView* ns_view = [ns_window contentView];
+  return (__bridge void*)ns_view;
+}