Improve ScreenInteractive wait function.

examples/component/menu.cpp

@@ -7,7 +7,7 @@
 
 int main(int argc, const char* argv[]) {
   using namespace ftxui;
-  auto screen = ScreenInteractive::FixedSize(30, 3);
+  auto screen = ScreenInteractive::TerminalOutput();
 
   Menu menu;
   menu.entries = {L"entry 1", L"entry 2", L"entry 3"};

include/ftxui/component/screen_interactive.hpp

@@ -40,7 +40,7 @@ class ScreenInteractive : public Screen {
    Dimension dimension_ = Dimension::Fixed;
    ScreenInteractive(int dimx, int dimy, Dimension dimension);
 
-   std::condition_variable events_queue_wait;
+   std::condition_variable events_queue_cv;
    std::mutex events_queue_mutex;
    std::queue<Event> events_queue;
    std::atomic<bool> quit_ = false;

src/ftxui/component/screen_interactive.cpp

@@ -74,22 +74,18 @@ ScreenInteractive ScreenInteractive::FitComponent() {
 void ScreenInteractive::PostEvent(Event event) {
   std::unique_lock<std::mutex> lock(events_queue_mutex);
   events_queue.push(event);
-  events_queue_wait.notify_one();
+  events_queue_cv.notify_one();
 }
 
 void ScreenInteractive::EventLoop(Component* component) {
-  bool handled = 0;
-  for (;;) {
   std::unique_lock<std::mutex> lock(events_queue_mutex);
+  while (!quit_ && events_queue.empty())
+    events_queue_cv.wait(lock);
+
+  // After the wait, we own the lock.
   while (!events_queue.empty()) {
     component->OnEvent(events_queue.front());
     events_queue.pop();
-      handled = true;
-    }
-
-    if (handled)
-      return;
-    events_queue_wait.wait(lock);
   }
 }