screen: use condition_variable rather than polling for next frame

Use a timeout to prevent deadlocks when unloading games/if no frames are prevented.

ares/ares/node/video/screen.cpp

@@ -25,11 +25,15 @@ Screen::~Screen() {
 
 auto Screen::main(uintptr_t) -> void {
   while(!_kill) {
-    usleep(1);
-    if(_frame) {
+    unique_lock<mutex> lock(_frameMutex);
+
+    auto timeout = std::chrono::milliseconds(10);
+    if(_frameCondition.wait_for(lock, timeout, [&] { return _frame.load(); })) {
       refresh();
       _frame = false;
     }
+
+    if(_kill) break;
   }
 }
 
@@ -181,10 +185,12 @@ auto Screen::frame() -> void {
 
   lock_guard<recursive_mutex> lock(_mutex);
   _inputA.swap(_inputB);
-  _frame = true;
   if constexpr(!ares::Video::Threaded) {
     refresh();
     _frame = false;
+  } else {
+    _frame = true;
+    _frameCondition.notify_one();
   }
 }
 

ares/ares/node/video/screen.hpp

@@ -97,6 +97,8 @@ protected:
 //unserialized:
   nall::thread _thread;
   recursive_mutex _mutex;
+  mutex _frameMutex;
+  condition_variable _frameCondition;
   atomic<bool> _kill = false;
   atomic<bool> _frame = false;
   function<void ()> _refresh;

nall/thread.hpp

@@ -13,8 +13,10 @@
 namespace nall {
   using mutex = std::mutex;
   using recursive_mutex = std::recursive_mutex;
+  using condition_variable = std::condition_variable;
   template<typename T> using lock_guard = std::lock_guard<T>;
   template<typename T> using atomic = std::atomic<T>;
+  template<typename T> using unique_lock = std::unique_lock<T>;
 }
 
 #if defined(API_POSIX)