Document VR ownership and GLFW platform hooks

src/platform_legacy/legacy_platform_services.cpp

@@ -94,6 +94,33 @@ public:
 #endif
 }
 
+#if defined(__LINUX__) || defined(__WEB__)
+struct RetainedLegacyGlfwWindowHooks final {
+    std::function<void()> acquire_render_context;
+    std::function<void()> present_render_context;
+    std::function<void()> request_app_close;
+};
+
+[[nodiscard]] RetainedLegacyGlfwWindowHooks& active_legacy_glfw_window_hooks()
+{
+    static RetainedLegacyGlfwWindowHooks hooks = [] {
+        RetainedLegacyGlfwWindowHooks retained;
+        GLFWwindow* const window = App::I->glfw_window;
+        retained.acquire_render_context = [window] {
+            glfwMakeContextCurrent(window);
+        };
+        retained.present_render_context = [window] {
+            glfwSwapBuffers(window);
+        };
+        retained.request_app_close = [window] {
+            glfwSetWindowShouldClose(window, GLFW_TRUE);
+        };
+        return retained;
+    }();
+    return hooks;
+}
+#endif
+
 #if defined(__IOS__) || defined(__OSX__)
 [[nodiscard]] NSMutableArray<NSString*>* apple_file_types_array(const std::vector<std::string>& file_types)
 {
@@ -412,7 +439,7 @@ public:
 #elif __ANDROID__
         android_async_lock();
 #elif __LINUX__ || __WEB__
-        glfwMakeContextCurrent(App::I->glfw_window);
+        active_legacy_glfw_window_hooks().acquire_render_context();
 #endif
     }
 
@@ -432,7 +459,7 @@ public:
 #elif __ANDROID__
         android_async_swap();
 #elif __LINUX__ || __WEB__
-        glfwSwapBuffers(App::I->glfw_window);
+        active_legacy_glfw_window_hooks().present_render_context();
 #endif
     }
 
@@ -743,7 +770,7 @@ public:
 #ifdef __OSX__
         active_apple_document_platform_services().request_app_close();
 #elif __LINUX__
-        glfwSetWindowShouldClose(App::I->glfw_window, GLFW_TRUE);
+        active_legacy_glfw_window_hooks().request_app_close();
 #endif
     }