use std::atomic instead of std::mutex

Author: mgood7123

NativeApp/include/Android/AndroidAppBase.hpp

@@ -26,7 +26,7 @@
 #pragma once
 
 #include <memory>
-#include <mutex>
+#include <atomic>
 
 #include <android_native_app_glue.h>
 #include "FlagEnum.h"
@@ -73,7 +73,7 @@ class AndroidAppBase : public AppBase
         APP_STATUS_FLAG_HAS_REAL_SURFACE = 0x00000008
     };
 
-    APP_STATUS_FLAGS app_status_ = APP_STATUS_FLAG_NONE;
+    std::atomic<APP_STATUS_FLAGS> app_status_ {APP_STATUS_FLAG_NONE};
 
 protected:
     virtual void Initialize()
@@ -104,8 +104,6 @@ class AndroidAppBase : public AppBase
     android_app* app_ = nullptr;
     std::string  native_activity_class_name_;
 
-    std::mutex mutex;
-
 private:
     void UpdatePosition(AInputEvent* event, int32_t iIndex, float& fX, float& fY);
     void SuspendSensors();
@@ -121,6 +119,23 @@ class AndroidAppBase : public AppBase
     ASensorManager*    sensor_manager_       = nullptr;
     const ASensor*     accelerometer_sensor_ = nullptr;
     ASensorEventQueue* sensor_event_queue_   = nullptr;
+    
+    class atomic_mutex {
+        std::atomic<bool> flag{false};
+    
+    public:
+        void lock()
+        {
+            while (flag.exchange(true, std::memory_order_relaxed));
+            std::atomic_thread_fence(std::memory_order_acquire);
+        }
+        
+        void unlock()
+        {
+            std::atomic_thread_fence(std::memory_order_release);
+            flag.store(false, std::memory_order_relaxed);
+        }
+    };
 };
 
 DEFINE_FLAG_ENUM_OPERATORS(AndroidAppBase::APP_STATUS_FLAGS)

NativeApp/src/Android/AndroidAppBase.cpp

@@ -129,22 +129,19 @@ void AndroidAppBase::HandleCmd(struct android_app* app, int32_t cmd)
                 LOG_INFO_MESSAGE("INIT DISPLAY - HAS SURFACE");
                 eng->InitDisplay();
                 eng->DrawFrame();
-                std::lock_guard<std::mutex> lock(eng->mutex);
-                eng->app_status_ |= APP_STATUS_FLAG_HAS_REAL_SURFACE;
+                eng->app_status_.store(eng->app_status_.load() | APP_STATUS_FLAG_HAS_REAL_SURFACE);
             }
             else
             {
                 LOG_INFO_MESSAGE("NO SURFACE");
-                std::lock_guard<std::mutex> lock(eng->mutex);
-                eng->app_status_ &= ~APP_STATUS_FLAG_HAS_REAL_SURFACE;
+                eng->app_status_.store(eng->app_status_.load() & ~APP_STATUS_FLAG_HAS_REAL_SURFACE);
             }
             break;
 
         case APP_CMD_TERM_WINDOW:
             LOG_INFO_MESSAGE("APP_CMD_TERM_WINDOW - LOST SURFACE - TERM DISPLAY");
             {
-                std::lock_guard<std::mutex> lock(eng->mutex);
-                eng->app_status_ &= ~APP_STATUS_FLAG_HAS_REAL_SURFACE;
+                eng->app_status_.store(eng->app_status_.load() & ~APP_STATUS_FLAG_HAS_REAL_SURFACE);
             }
             eng->TermDisplay();
             break;
@@ -186,26 +183,23 @@ void AndroidAppBase::HandleCmd(struct android_app* app, int32_t cmd)
         case APP_CMD_GAINED_FOCUS:
             LOG_INFO_MESSAGE("APP_CMD_GAINED_FOCUS - HAS FOCUS");
             {
-                std::lock_guard<std::mutex> lock(eng->mutex);
-                eng->app_status_ |= APP_STATUS_FLAG_FOCUSED;
+                eng->app_status_.store(eng->app_status_.load() | APP_STATUS_FLAG_FOCUSED);
             }
             eng->ResumeSensors();
             break;
 
         case APP_CMD_LOST_FOCUS:
             LOG_INFO_MESSAGE("APP_CMD_LOST_FOCUS - LOST FOCUS");
             {
-                std::lock_guard<std::mutex> lock(eng->mutex);
-                eng->app_status_ &= ~APP_STATUS_FLAG_FOCUSED;
+                eng->app_status_.store(eng->app_status_.load() & ~APP_STATUS_FLAG_FOCUSED);
             }
             eng->SuspendSensors();
             break;
 
         case APP_CMD_RESUME:
             LOG_INFO_MESSAGE("APP_CMD_RESUME - IS ACTIVE");
             {
-                std::lock_guard<std::mutex> lock(eng->mutex);
-                eng->app_status_ |= APP_STATUS_FLAG_ACTIVE;
+                eng->app_status_.store(eng->app_status_.load() | APP_STATUS_FLAG_ACTIVE);
             }
             break;
 
@@ -216,8 +210,7 @@ void AndroidAppBase::HandleCmd(struct android_app* app, int32_t cmd)
         case APP_CMD_PAUSE:
             LOG_INFO_MESSAGE("APP_CMD_PAUSE - IS NOT ACTIVE");
             {
-                std::lock_guard<std::mutex> lock(eng->mutex);
-                eng->app_status_ &= ~APP_STATUS_FLAG_ACTIVE;
+                eng->app_status_.store(eng->app_status_.load() & ~APP_STATUS_FLAG_ACTIVE);
             }
             break;
 
@@ -235,8 +228,7 @@ void AndroidAppBase::HandleCmd(struct android_app* app, int32_t cmd)
         case APP_CMD_DESTROY:
             LOG_INFO_MESSAGE("APP_CMD_DESTROY - IS NOT RUNNING");
             {
-                std::lock_guard<std::mutex> lock(eng->mutex);
-                eng->app_status_ &= ~APP_STATUS_FLAG_RUNNING;
+                eng->app_status_.store(eng->app_status_.load() & ~APP_STATUS_FLAG_RUNNING);
             }
             break;
 
@@ -312,11 +304,11 @@ void AndroidAppBase::SetState(android_app* state, const char* native_activity_cl
 
 bool AndroidAppBase::IsReady()
 {
-    std::lock_guard<std::mutex> lock(mutex);
-    return (app_status_ & APP_STATUS_FLAG_RUNNING) != APP_STATUS_FLAG_NONE &&
-        (app_status_ & APP_STATUS_FLAG_ACTIVE) != APP_STATUS_FLAG_NONE &&
-        (app_status_ & APP_STATUS_FLAG_FOCUSED) != APP_STATUS_FLAG_NONE &&
-        (app_status_ & APP_STATUS_FLAG_HAS_REAL_SURFACE) != APP_STATUS_FLAG_NONE;
+    APP_STATUS_FLAGS app_status = app_status_.load();
+    return (app_status & APP_STATUS_FLAG_RUNNING) != APP_STATUS_FLAG_NONE &&
+        (app_status & APP_STATUS_FLAG_ACTIVE) != APP_STATUS_FLAG_NONE &&
+        (app_status & APP_STATUS_FLAG_FOCUSED) != APP_STATUS_FLAG_NONE &&
+        (app_status & APP_STATUS_FLAG_HAS_REAL_SURFACE) != APP_STATUS_FLAG_NONE;
 }
 
 //void Engine::TransformPosition( ndk_helper::Vec2& vec )