Workaround for promise continuations (#89)

Author: bghgary

Modules/@babylonjs/react-native/EngineHook.ts

@@ -75,14 +75,6 @@ export function useEngine(): Engine | undefined {
             }
         })();
 
-        // NOTE: This is a workaround for https://github.com/BabylonJS/BabylonReactNative/issues/60
-        function heartbeat() {
-            if (!disposed) {
-                setTimeout(heartbeat, 10);
-            }
-        }
-        heartbeat();
-
         return () => {
             disposed = true;
             setEngine(engine => {

Modules/@babylonjs/react-native/android/src/main/cpp/BabylonNativeInterop.cpp

@@ -22,6 +22,8 @@
 
 #include <jsi/jsi.h>
 
+#include "../../../../shared/Shared.h"
+
 namespace Babylon
 {
     namespace
@@ -39,14 +41,29 @@ namespace Babylon
         Native(facebook::jsi::Runtime* jsiRuntime, ANativeWindow* windowPtr)
             : m_env{ Napi::Attach<facebook::jsi::Runtime&>(*jsiRuntime) }
         {
-            auto looper_scheduler = std::make_shared<looper_scheduler_t>(looper_scheduler_t::get_for_current_thread());
+            struct DispatchData
+            {
+                using looper_scheduler_t = arcana::looper_scheduler<128>;
+
+                looper_scheduler_t scheduler;
+                Napi::FunctionReference flushedQueue;
 
-            JsRuntime::DispatchFunctionT dispatchFunction{[env = m_env, looper_scheduler = std::move(looper_scheduler)](std::function<void(Napi::Env)> func) {
-                (*looper_scheduler)([env, func = std::move(func)]()
+                DispatchData(Napi::Env env)
+                    : scheduler{ looper_scheduler_t::get_for_current_thread() }
+                    , flushedQueue{ GetFlushedQueue(env) }
                 {
-                    func(env);
-                });
-            }};
+                }
+            };
+
+            JsRuntime::DispatchFunctionT dispatchFunction =
+                [env = m_env, data = std::make_shared<DispatchData>(m_env)](std::function<void(Napi::Env)> func)
+                {
+                    (data->scheduler)([env, func = std::move(func), &data]()
+                    {
+                        func(env);
+                        data->flushedQueue.Call({});
+                    });
+                };
 
             m_runtime = &JsRuntime::CreateForJavaScript(m_env, dispatchFunction);
 
@@ -100,8 +117,6 @@ namespace Babylon
         }
 
     private:
-        using looper_scheduler_t = arcana::looper_scheduler<sizeof(std::weak_ptr<Napi::Env>) + sizeof(std::function<void(Napi::Env)>)>;
-
         std::unique_ptr<Graphics> m_graphics{};
         Napi::Env m_env;
         JsRuntime* m_runtime;

Modules/@babylonjs/react-native/ios/BabylonNative.cpp

@@ -18,6 +18,8 @@
 #include <sstream>
 #include <unistd.h>
 
+#include "../shared/Shared.h"
+
 namespace Babylon
 {
     using namespace facebook;
@@ -43,15 +45,27 @@ namespace Babylon
             m_impl->m_graphics = Graphics::InitializeFromWindow<void*>(windowPtr, width, height);
         });
 
-        auto run_loop_scheduler = std::make_shared<arcana::run_loop_scheduler>(arcana::run_loop_scheduler::get_for_current_thread());
-
-        JsRuntime::DispatchFunctionT dispatchFunction{[env = m_impl->env, run_loop_scheduler = std::move(run_loop_scheduler)](std::function<void(Napi::Env)> func)
+        struct DispatchData
         {
-            (*run_loop_scheduler)([env, func = std::move(func)]()
+            arcana::run_loop_scheduler scheduler;
+            Napi::FunctionReference flushedQueue;
+
+            DispatchData(Napi::Env env)
+                : scheduler{ arcana::run_loop_scheduler::get_for_current_thread() }
+                , flushedQueue{ GetFlushedQueue(env) }
+            {
+            }
+        };
+
+        JsRuntime::DispatchFunctionT dispatchFunction =
+            [env = m_impl->env, data = std::make_shared<DispatchData>(m_impl->env)](std::function<void(Napi::Env)> func)
             {
-                func(env);
-            });
-        }};
+                (data->scheduler)([env, func = std::move(func), &data]()
+                {
+                    func(env);
+                    data->flushedQueue.Call({});
+                });
+            };
 
         m_impl->runtime = &JsRuntime::CreateForJavaScript(m_impl->env, std::move(dispatchFunction));
 

Modules/@babylonjs/react-native/shared/Shared.h

@@ -0,0 +1,18 @@
+#pragma once
+
+#include <napi/napi.h>
+
+// See https://github.com/BabylonJS/BabylonReactNative/issues/60 for original issue.
+// This is a work around to poke the React Native message queue to run setImmediate callbacks.
+// React Native uses a custom promise implementation based on setImmediate. The promise
+// continuations will only continue once these setImmediate callbacks are triggered by the
+// flushedQueue call. This is explicitly called at the end of JsRuntime's dispatch function
+// to flush the queue.
+inline Napi::FunctionReference GetFlushedQueue(Napi::Env env)
+{
+    // HACK: The __fbBatchedBridge global is an internal implementation of React Native.
+    // This hack will break if React Native internals changes, but it should blow up right here.
+    auto batchedBridge{ env.Global().Get("__fbBatchedBridge").As<Napi::Object>() };
+    auto flushedQueue{ batchedBridge.Get("flushedQueue").As<Napi::Function>() };
+    return Napi::Persistent(flushedQueue);
+}