core: rework event loop for polling and C++-style awaits

Stops the event loop from checking all the time in favor of locks and polling.

src/core/PortalManager.cpp

@@ -290,27 +290,108 @@ void CPortalManager::init() {
 
     wl_display_roundtrip(m_sWaylandConnection.display);
 
+    startEventLoop();
+}
+
+void CPortalManager::startEventLoop() {
+
+    pollfd pollfds[] = {
+        {
+            .fd     = m_pConnection->getEventLoopPollData().fd,
+            .events = POLLIN,
+        },
+        {
+            .fd     = wl_display_get_fd(m_sWaylandConnection.display),
+            .events = POLLIN,
+        },
+        {
+            .fd     = pw_loop_get_fd(m_sPipewire.loop),
+            .events = POLLIN,
+        },
+    };
+
+    std::thread pollThr([this, &pollfds]() {
         while (1) {
-        // dbus events
+            int ret = poll(pollfds, 3, -1);
+            if (ret < 0) {
+                Debug::log(CRIT, "[core] Polling fds failed with {}", strerror(errno));
+                exit(1);
+            }
+
+            for (size_t i = 0; i < 3; ++i) {
+                if (pollfds[0].revents & POLLHUP) {
+                    Debug::log(CRIT, "[core] Disconnected from pollfd id {}", i);
+                    exit(1);
+                }
+            }
+
+            {
+                Debug::log(TRACE, "[core] got poll event");
+                std::lock_guard<std::mutex> lg(m_sEventLoopInternals.loopRequestMutex);
+                m_sEventLoopInternals.shouldProcess = true;
+                m_sEventLoopInternals.loopSignal.notify_all();
+            }
+        }
+    });
+
+    m_sTimersThread.thread = std::make_unique<std::thread>([this] {
+        while (1) {
+            std::unique_lock lk(m_sTimersThread.loopMutex);
+
+            // find nearest timer ms
+            m_mEventLock.lock();
+            float nearest = 60000; /* reasonable timeout */
+            for (auto& t : m_sTimersThread.timers) {
+                float until = t->duration() - t->passedMs();
+                if (until < nearest)
+                    nearest = until;
+            }
+            m_mEventLock.unlock();
+
+            m_sTimersThread.loopSignal.wait_for(lk, std::chrono::milliseconds((int)nearest), [this] { return m_sTimersThread.shouldProcess; });
+            m_sTimersThread.shouldProcess = false;
+
+            // awakened. Check if any timers passed
+            m_mEventLock.lock();
+            bool notify = false;
+            for (auto& t : m_sTimersThread.timers) {
+                if (t->passed()) {
+                    Debug::log(TRACE, "[core] got timer event");
+                    notify = true;
+                    break;
+                }
+            }
+            m_mEventLock.unlock();
+
+            if (notify) {
+                std::lock_guard<std::mutex> lg(m_sEventLoopInternals.loopRequestMutex);
+                m_sEventLoopInternals.shouldProcess = true;
+                m_sEventLoopInternals.loopSignal.notify_all();
+            }
+        }
+    });
+
+    while (1) { // dbus events
+        // wait for being awakened
+        m_sEventLoopInternals.loopRequestMutex.unlock(); // unlock, we are ready to take events
+
+        std::unique_lock lk(m_sEventLoopInternals.loopMutex);
+        if (m_sEventLoopInternals.shouldProcess == false) // avoid a lock if a thread managed to request something already since we .unlock()ed
+            m_sEventLoopInternals.loopSignal.wait(lk, [this] { return m_sEventLoopInternals.shouldProcess == true; }); // wait for events
+
+        m_sEventLoopInternals.loopRequestMutex.lock(); // lock incoming events
+
+        m_sEventLoopInternals.shouldProcess = false;
+
         m_mEventLock.lock();
 
+        if (pollfds[0].revents & POLLIN /* dbus */) {
             while (m_pConnection->processPendingRequest()) {
                 ;
             }
-
-        std::vector<CTimer*> toRemove;
-        for (auto& t : m_vTimers) {
-            if (t->passed()) {
-                t->m_fnCallback();
-                toRemove.emplace_back(t.get());
-                Debug::log(TRACE, "[core] calling timer {}", (void*)t.get());
-            }
-        }
-
-        while (pw_loop_iterate(m_sPipewire.loop, 0) != 0) {
-            ;
         }
 
+        if (pollfds[1].revents & POLLIN /* wl */) {
             wl_display_flush(m_sWaylandConnection.display);
             if (wl_display_prepare_read(m_sWaylandConnection.display) == 0) {
                 wl_display_read_events(m_sWaylandConnection.display);
@@ -318,15 +399,38 @@ void CPortalManager::init() {
             } else {
                 wl_display_dispatch(m_sWaylandConnection.display);
             }
+        }
+
+        if (pollfds[2].revents & POLLIN /* pw */) {
+            while (pw_loop_iterate(m_sPipewire.loop, 0) != 0) {
+                ;
+            }
+        }
+
+        std::vector<CTimer*> toRemove;
+        for (auto& t : m_sTimersThread.timers) {
+            if (t->passed()) {
+                t->m_fnCallback();
+                toRemove.emplace_back(t.get());
+                Debug::log(TRACE, "[core] calling timer {}", (void*)t.get());
+            }
+        }
+
+        // finalize wayland dispatching. Dispatch pending on the queue
+        int ret = 0;
+        do {
+            ret = wl_display_dispatch_pending(m_sWaylandConnection.display);
+            wl_display_flush(m_sWaylandConnection.display);
+        } while (ret > 0);
 
         if (!toRemove.empty())
-            std::erase_if(m_vTimers,
+            std::erase_if(m_sTimersThread.timers,
                           [&](const auto& t) { return std::find_if(toRemove.begin(), toRemove.end(), [&](const auto& other) { return other == t.get(); }) != toRemove.end(); });
 
         m_mEventLock.unlock();
-
-        std::this_thread::sleep_for(std::chrono::milliseconds(1));
     }
+
+    m_sTimersThread.thread.release();
 }
 
 sdbus::IConnection* CPortalManager::getConnection() {
@@ -382,3 +486,10 @@ gbm_device* CPortalManager::createGBMDevice(drmDevice* dev) {
     free(renderNode);
     return gbm_create_device(fd);
 }
+
+void CPortalManager::addTimer(const CTimer& timer) {
+    Debug::log(TRACE, "[core] adding timer for {}ms", timer.duration());
+    m_sTimersThread.timers.emplace_back(std::make_unique<CTimer>(timer));
+    m_sTimersThread.shouldProcess = true;
+    m_sTimersThread.loopSignal.notify_all();
+}

src/core/PortalManager.hpp

@@ -67,11 +67,28 @@ class CPortalManager {
 
     std::vector<SDMABUFModifier> m_vDMABUFMods;
 
-    std::vector<std::unique_ptr<CTimer>> m_vTimers;
+    void                         addTimer(const CTimer& timer);
 
     gbm_device*                  createGBMDevice(drmDevice* dev);
 
   private:
+    void startEventLoop();
+
+    struct {
+        std::condition_variable loopSignal;
+        std::mutex              loopMutex;
+        std::atomic<bool>       shouldProcess = false;
+        std::mutex              loopRequestMutex;
+    } m_sEventLoopInternals;
+
+    struct {
+        std::condition_variable              loopSignal;
+        std::mutex                           loopMutex;
+        bool                                 shouldProcess = false;
+        std::vector<std::unique_ptr<CTimer>> timers;
+        std::unique_ptr<std::thread>         thread;
+    } m_sTimersThread;
+
     std::unique_ptr<sdbus::IConnection>   m_pConnection;
     std::vector<std::unique_ptr<SOutput>> m_vOutputs;
 

src/helpers/Timer.cpp

@@ -9,3 +9,11 @@ CTimer::CTimer(float ms, std::function<void()> callback) {
 bool CTimer::passed() const {
     return std::chrono::high_resolution_clock::now() > (m_tStart + std::chrono::milliseconds((uint64_t)m_fDuration));
 }
+
+float CTimer::passedMs() const {
+    return std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::high_resolution_clock::now() - m_tStart).count();
+}
+
+float CTimer::duration() const {
+    return m_fDuration;
+}

src/helpers/Timer.hpp

@@ -8,6 +8,8 @@ class CTimer {
     CTimer(float ms, std::function<void()> callback);
 
     bool                  passed() const;
+    float                 passedMs() const;
+    float                 duration() const;
 
     std::function<void()> m_fnCallback;
 

src/portals/Screencopy.cpp

@@ -654,8 +654,7 @@ void CScreencopyPortal::queueNextShareFrame(CScreencopyPortal::SSession* pSessio
     if (PSTREAM && !PSTREAM->streamState)
         return;
 
-    g_pPortalManager->m_vTimers.emplace_back(
+    g_pPortalManager->addTimer({1000.0 / pSession->sharingData.framerate, [pSession]() { g_pPortalManager->m_sPortals.screencopy->startFrameCopy(pSession); }});
-        std::make_unique<CTimer>(1000.0 / pSession->sharingData.framerate, [pSession]() { g_pPortalManager->m_sPortals.screencopy->startFrameCopy(pSession); }));
 }
 bool CScreencopyPortal::hasToplevelCapabilities() {
     return m_sState.toplevel;