Wake up main thread immediately after new frame is pushed

app/streaming/sdlhelper.cpp

@@ -0,0 +1,45 @@
+#include "sdlhelper.h"
+
+SDL_cond* SDLHelper::s_EventCond;
+SDL_mutex* SDLHelper::s_EventMutex;
+
+void SDLHelper::initializeIfNeeded()
+{
+    if (!s_EventCond) {
+        s_EventCond = SDL_CreateCond();
+    }
+    if (!s_EventMutex) {
+        s_EventMutex = SDL_CreateMutex();
+    }
+}
+
+void SDLHelper::waitEvent(SDL_Event* event)
+{
+    initializeIfNeeded();
+
+    // We explicitly use SDL_PollEvent() and SDL_Delay() because
+    // SDL_WaitEventTimeout() has an internal SDL_Delay(10) inside which
+    // blocks this thread too long for high polling rate mice and high
+    // refresh rate displays.
+    while (!SDL_PollEvent(event)) {
+        // Sleep for up to 1 ms or until we are woken up by
+        // SDLHelper::pushEvent().
+        // FIXME: SDL should do this internally
+        SDL_LockMutex(s_EventMutex);
+        SDL_CondWaitTimeout(s_EventCond, s_EventMutex, 1);
+        SDL_UnlockMutex(s_EventMutex);
+        continue;
+    }
+}
+
+void SDLHelper::pushEvent(SDL_Event* event)
+{
+    initializeIfNeeded();
+
+    SDL_PushEvent(event);
+
+    // Immediately wake up the other waiting thread
+    SDL_LockMutex(s_EventMutex);
+    SDL_CondSignal(s_EventCond);
+    SDL_UnlockMutex(s_EventMutex);
+}