[fix] correct video latency measurement and smooth connection RTT

apps/desktop/src/app/main.cpp

@@ -23,6 +23,7 @@
 #include "config_center.h"
 #include "daemon.h"
 #include "path_manager.h"
+#include "platform/single_instance.h"
 #include "rd_log.h"
 #include "render.h"
 
@@ -183,28 +184,34 @@ int HandleServiceCliCommand(const std::string& command) {
 }  // namespace
 #endif
 
-static int RunApplication(int argc, char* argv[]) {
-  // Service operations and config migration can log before the GUI starts.
-  // Configure the directory first, including CLI and daemon child paths.
+static bool IsDaemonChild(int argc, char* argv[]) {
+  for (int i = 1; i < argc; ++i) {
+    if (std::strcmp(argv[i], "--child") == 0) return true;
+  }
+  return false;
+}
+
+static crossdesk::platform::InstanceResult AcquireInstance(
+    crossdesk::platform::SingleInstanceGuard& guard,
+    crossdesk::platform::InstanceRole role) {
+  std::string error;
+  const auto result = guard.TryAcquire(role, error);
+  if (result == crossdesk::platform::InstanceResult::kAlreadyRunning) {
+    std::cerr << "CrossDesk is already running for this user.\n";
+  } else if (result == crossdesk::platform::InstanceResult::kError) {
+    std::cerr << "CrossDesk cannot start: " << error << '\n';
+  }
+  return result;
+}
+
+static int RunApplication(
+    int argc, char* argv[],
+    crossdesk::platform::SingleInstanceGuard& client_instance) {
+  // The instance guards are held before any configuration or logger is opened.
   auto path_manager = std::make_unique<crossdesk::PathManager>("CrossDesk");
   crossdesk::InitLogger(path_manager->GetLogPath().string());
 
-#ifdef _WIN32
-  if (argc > 1 && IsServiceCliCommand(argv[1])) {
-    return HandleServiceCliCommand(argv[1]);
-  }
-#endif
-
-  // check if running as child process
-  bool is_child = false;
-  for (int i = 1; i < argc; i++) {
-    if (strcmp(argv[i], "--child") == 0) {
-      is_child = true;
-      break;
-    }
-  }
-
-  if (is_child) {
+  if (IsDaemonChild(argc, argv)) {
     // child process: run render directly
     crossdesk::Render render;
     return render.Run();
@@ -230,11 +237,23 @@ static int RunApplication(int argc, char* argv[]) {
 #endif
 
   if (enable_daemon) {
+    // The launcher lease stays in main for the supervisor's entire lifetime.
+    // Each --child must acquire its own client lease, so it is neither blocked
+    // by its supervisor nor able to bypass the single-client restriction.
+    client_instance.Release();
     // start daemon with restart monitoring
     Daemon daemon("CrossDesk");
 
     // define main loop function: run render and stop daemon on normal exit
-    Daemon::MainLoopFunc main_loop = [&daemon]() {
+    Daemon::MainLoopFunc main_loop = [&daemon, &client_instance]() {
+      // Executable discovery can fail and make the supervisor run the GUI in
+      // process. This fallback must retain the same client ownership rule.
+      if (AcquireInstance(client_instance,
+                          crossdesk::platform::InstanceRole::kClient) !=
+          crossdesk::platform::InstanceResult::kAcquired) {
+        daemon.stop();
+        return;
+      }
       crossdesk::Render render;
       render.Run();
       daemon.stop();
@@ -267,26 +286,51 @@ int main(int argc, char* argv[]) {
     std::cout << console.Text("console_cli_help");
     return 0;
   }
-  const int result = crossdesk::RunWithLinuxDisplay(
-      argc, argv, [&] { return RunApplication(argc, argv); }, [&] {
+#endif
+#ifdef _WIN32
+  if (argc == 2 &&
+      std::strcmp(argv[1], crossdesk::kSlintRendererProbeArgument) == 0) {
+    return crossdesk::RunSlintRendererProbe();
+  }
+  if (argc > 1 && IsServiceCliCommand(argv[1])) {
+    EnsureConsoleForCli();
+    crossdesk::platform::SingleInstanceGuard cli_instance;
+    if (AcquireInstance(cli_instance, crossdesk::platform::InstanceRole::kServiceCli) !=
+        crossdesk::platform::InstanceResult::kAcquired) return 1;
+    crossdesk::PathManager paths("CrossDesk");
+    crossdesk::InitLogger(paths.GetLogPath().string(), "crossdesk-service-cli");
+    return HandleServiceCliCommand(argv[1]);
+  }
+#endif
+
+  using crossdesk::platform::InstanceResult;
+  using crossdesk::platform::InstanceRole;
+  crossdesk::platform::SingleInstanceGuard launcher_instance;
+  crossdesk::platform::SingleInstanceGuard client_instance;
+  if (!IsDaemonChild(argc, argv)) {
+    const auto result = AcquireInstance(launcher_instance, InstanceRole::kLauncher);
+    if (result != InstanceResult::kAcquired)
+      return result == InstanceResult::kAlreadyRunning ? 0 : 1;
+  }
+  const auto result = AcquireInstance(client_instance, InstanceRole::kClient);
+  if (result != InstanceResult::kAcquired)
+    return result == InstanceResult::kAlreadyRunning ? 0 : 1;
+
+#ifdef __linux__
+  const int exit_code = crossdesk::RunWithLinuxDisplay(
+      argc, argv, [&] { return RunApplication(argc, argv, client_instance); }, [&] {
         crossdesk::PathManager paths("CrossDesk");
         if (console.Enable(paths.GetLogPath(), paths.GetCachePath() / "config.ini")) return true;
         std::cerr << "无法初始化日志或控制台，启动失败。\n";
         return false;
       });
   if (console.active()) {
-    console.Notify(result == 0 ? console.Text("console_exited")
-        : console.Text("console_stopped") + " " + std::to_string(result) +
+    console.Notify(exit_code == 0 ? console.Text("console_exited")
+        : console.Text("console_stopped") + " " + std::to_string(exit_code) +
           "; " + console.Text("console_log_file") + ": " + console.diagnostic_path());
   }
-  return result;
+  return exit_code;
 #else
-#ifdef _WIN32
-  if (argc == 2 &&
-      std::strcmp(argv[1], crossdesk::kSlintRendererProbeArgument) == 0) {
-    return crossdesk::RunSlintRendererProbe();
-  }
-#endif
-  return RunApplication(argc, argv);
+  return RunApplication(argc, argv, client_instance);
 #endif
 }

apps/desktop/src/gui/application/gui_application.cpp

@@ -2029,7 +2029,7 @@ void GuiApplication::ShareLocalCursorState() {
     if (!delivery.has_sent ||
         delivery.last_sent.render_mode != outgoing.render_mode ||
         delivery.last_sent.hidden_reason != outgoing.hidden_reason) {
-      LOG_INFO("Send cursor presentation to [{}]: mode={}, reason={}",
+      LOG_DEBUG("Send cursor presentation to [{}]: mode={}, reason={}",
                recipient.remote_id, static_cast<int>(outgoing.render_mode),
                static_cast<int>(outgoing.hidden_reason));
     }
@@ -2803,7 +2803,7 @@ void GuiApplication::SyncStreamWindow() {
   ui_->display_model->set_vector(std::move(displays));
   (*ui_->stream)->set_selected_display(props->selected_display_);
 
-  const auto& net = props->net_traffic_stats_;
+  const auto net = props->net_traffic_stats_.Load();
   (*ui_->stream)->set_stats_encryption_enabled(
       status == ConnectionStatus::Connected && net.srtp_active);
   std::vector<ui::NetworkStatsRow> stats_rows;
@@ -2892,12 +2892,14 @@ void GuiApplication::SyncStreamWindow() {
           props->file_transfer_.file_transfer_window_visible_);
 
   const auto fps_now = std::chrono::steady_clock::now();
+  bool refresh_stats = false;
   if (!props->net_traffic_stats_button_pressed_) {
     props->fps_ = 0;
     props->frame_count_ = 0;
     props->last_time_ = {};
   } else if (props->last_time_.time_since_epoch().count() == 0) {
     props->last_time_ = fps_now;
+    refresh_stats = true;
   } else {
     const auto elapsed = std::chrono::duration_cast<std::chrono::milliseconds>(
                              fps_now - props->last_time_)
@@ -2906,9 +2908,42 @@ void GuiApplication::SyncStreamWindow() {
       props->fps_ = static_cast<int>(props->frame_count_ * 1000 / elapsed);
       props->frame_count_ = 0;
       props->last_time_ = fps_now;
+      refresh_stats = true;
     }
   }
   (*ui_->stream)->set_stats_fps(UiText(std::to_string(props->fps_)));
+  if (!props->net_traffic_stats_button_pressed_ ||
+      status != ConnectionStatus::Connected) {
+    props->video_latency_snapshot_.reset();
+  } else if (refresh_stats) {
+    props->video_latency_snapshot_ = props->video_latency_->Get(fps_now);
+  }
+  const auto& latency = props->video_latency_snapshot_;
+  (*ui_->stream)
+      ->set_stats_video_latency(UiText(
+          latency ? std::to_string(
+                        static_cast<int>(std::lround(latency->average_ms))) +
+                        " ms"
+                  : "—"));
+  const auto display_rtt = props->net_traffic_stats_.SmoothedRttMs(fps_now);
+  const bool rtt_available = props->net_traffic_stats_button_pressed_ &&
+                            status == ConnectionStatus::Connected &&
+                            display_rtt.has_value();
+  std::string connection_latency = "—";
+  if (rtt_available) {
+    connection_latency =
+        *display_rtt < 1
+            ? "<1 ms"
+            : std::to_string(static_cast<int>(std::lround(*display_rtt))) + " ms";
+  }
+  (*ui_->stream)->set_stats_connection_latency(UiText(connection_latency));
+  if (refresh_stats && status == ConnectionStatus::Connected) {
+    LOG_DEBUG("Latency stats: remote={} video_ms={} video_samples={} "
+              "rtt_raw_ms={} rtt_display_ms={}",
+              props->remote_id_, latency ? latency->average_ms : -1,
+              latency ? latency->samples : 0, net.rtt_ms,
+              display_rtt.value_or(-1));
+  }
 }
 
 void GuiApplication::SyncStreamVideoFrame() {
@@ -2928,6 +2963,7 @@ void GuiApplication::SyncStreamVideoFrame() {
     frame.width = props->video_width_;
     frame.height = props->video_height_;
     frame.sequence = props->video_frame_sequence_;
+    frame.timing = props->video_frame_timing_;
   }
 
   const auto result = ui_->video_presenter->Present(frame);

apps/desktop/src/gui/assets/localization/localization_data.h

@@ -305,6 +305,8 @@ struct TranslationRow {
     "File Transfer Save Path:", u8"Путь сохранения файлов:")                   \
   X(default_desktop, u8"桌面", "Desktop", u8"Рабочий стол")                    \
   X(resolution, u8"分辨率", "Res", u8"Разрешение")                             \
+  X(video_latency, u8"视频延时", "Video delay", u8"Задержка") \
+  X(connection_latency, u8"连接延时", "Connection RTT", u8"Задержка соединения") \
   X(connection_mode, u8"连接模式", "Mode", u8"Режим")                          \
   X(connection_mode_direct, u8"直连", "Direct", u8"Прямой")                    \
   X(connection_mode_relay, u8"中继", "Relay", u8"Релейный")                    \

apps/desktop/src/gui/features/devices/session_device_manager.cpp

@@ -82,7 +82,7 @@ void SessionDeviceManager::RecordCaptureCadence(
                            : capture_secure_callbacks_ == capture_callbacks_
                                ? "secure_desktop"
                                : "mixed";
-      LOG_INFO(
+      LOG_DEBUG(
           "Capture delivery: source={} normal_callbacks={} secure_callbacks={} "
           "target_fps={} input_fps={:.2f} "
           "forwarded_fps={:.2f} callbacks={} rate_dropped={} "
@@ -225,7 +225,7 @@ int SessionDeviceManager::InitializeScreenCapturer() {
                                     last_video_frame_stream_id_ != stream_id;
         if (resumed_after_gap || stream_changed) {
           if (RequestVideoKeyFrame(owner_.peer_, stream_id.c_str()) == 0) {
-            LOG_INFO("Request video key frame before sending captured frame, "
+            LOG_DEBUG("Request video key frame before sending captured frame, "
                      "stream='{}', gap_ms={}, stream_changed={}",
                      stream_id, duration_ms, stream_changed);
           }

apps/desktop/src/gui/features/file_transfer/file_transfer_manager.cpp

@@ -298,7 +298,7 @@ void FileTransferManager::HandleAck(const char *data, size_t size) {
   uint32_t rate_bps = 0;
   if (props) {
     const uint32_t bitrate =
-        props->net_traffic_stats_.data_outbound_stats.bitrate;
+        props->net_traffic_stats_.DataOutboundBitrate();
     if (bitrate > 0 && state->file_sending_.load()) {
       rate_bps = static_cast<uint32_t>(bitrate * 0.99f);
       const uint32_t current_rate = state->file_send_rate_bps_.load();

apps/desktop/src/gui/rendering/slint_video_presenter.cpp

@@ -87,6 +87,7 @@ struct SlintVideoPresenter::Impl {
   VideoRenderSize gl_image_size;
   VideoRenderSize gl_pending_size;
   bool gl_pending_dirty = false;
+  VideoLatencyFrame gl_pending_timing;
 #endif
 
   SurfaceState CurrentState() const {
@@ -192,6 +193,7 @@ struct SlintVideoPresenter::Impl {
             glPixelStorei(GL_UNPACK_ALIGNMENT, previous_unpack_alignment);
             glBindTexture(GL_TEXTURE_2D, static_cast<GLuint>(previous_texture));
             gl_pending_dirty = false;
+            gl_pending_timing.MarkSubmitted();
             return;
           }
 
@@ -322,7 +324,7 @@ SlintVideoPresenter::PresentResult SlintVideoPresenter::Present(
       impl_->seeded_frame_sequence[frame.remote_id] != frame.sequence) {
     const auto submit_result = impl_->renderer.SubmitCachedNv12(
         frame.remote_id, frame.nv12->data(), frame.nv12->size(), frame.width,
-        frame.height);
+        frame.height, frame.timing);
     if (submit_result == VideoRenderer::SubmitResult::submitted ||
         submit_result == VideoRenderer::SubmitResult::dropped) {
       impl_->seeded_frame_sequence[frame.remote_id] = frame.sequence;
@@ -440,6 +442,7 @@ SlintVideoPresenter::PresentResult SlintVideoPresenter::Present(
       impl_->gl_pending_frame.swap(impl_->gl_conversion_frame);
       impl_->gl_pending_size = {output_width, output_height};
       impl_->gl_pending_dirty = true;
+      impl_->gl_pending_timing = frame.timing;
     }
     const VideoRenderSize output_size{output_width, output_height};
     if (impl_->gl_image_size != output_size) {
@@ -469,6 +472,7 @@ SlintVideoPresenter::PresentResult SlintVideoPresenter::Present(
   }
 
   (*impl_->stream)->set_frame(slint::Image(std::move(pixels)));
+  frame.timing.MarkSubmitted();
   (*impl_->stream)->set_has_frame(true);
   (*impl_->stream)->set_receiving_text("");
   result.width = frame.width;

apps/desktop/src/gui/rendering/slint_video_presenter.h

@@ -14,6 +14,8 @@
 #include <string>
 #include <vector>
 
+#include "rendering/video_latency.h"
+
 namespace slint {
 template <typename T> class ComponentHandle;
 }
@@ -42,6 +44,7 @@ public:
     int width = 0;
     int height = 0;
     uint64_t sequence = 0;
+    VideoLatencyFrame timing;
   };
 
   struct PresentResult {

apps/desktop/src/gui/rendering/video_latency.h

@@ -0,0 +1,110 @@
+/*
+ * @Author: DI JUNKUN
+ * @Date: 2026-09-26
+ * Copyright (c) 2026 by DI JUNKUN, All Rights Reserved.
+ */
+
+#ifndef _VIDEO_LATENCY_H_
+#define _VIDEO_LATENCY_H_
+
+#include <chrono>
+#include <cstddef>
+#include <cstdint>
+#include <deque>
+#include <memory>
+#include <mutex>
+#include <optional>
+
+namespace crossdesk {
+
+class VideoLatencyStats;
+
+// Travels with the exact queued pixels, including native frames. Its clock is
+// translated once at the receive callback; rendering needs no live PeerPtr.
+struct VideoLatencyFrame {
+  using Clock = std::chrono::steady_clock;
+  std::shared_ptr<VideoLatencyStats> stats;
+  uint64_t id = 0;
+  Clock::time_point capture_time{};
+  void MarkPresented(Clock::time_point now = Clock::now()) const;
+  // Fallback for renderers which expose submission but no presentation time.
+  void MarkSubmitted(Clock::time_point now = Clock::now()) const;
+};
+
+class VideoLatencyStats
+    : public std::enable_shared_from_this<VideoLatencyStats> {
+ public:
+  using Clock = VideoLatencyFrame::Clock;
+  struct Snapshot {
+    double average_ms;
+    size_t samples;
+  };
+
+  VideoLatencyFrame Frame(uint64_t captured_us, int64_t local_now_us,
+                          Clock::time_point now = Clock::now()) {
+    if (captured_us == 0 || local_now_us <= 0 ||
+        captured_us > uint64_t(local_now_us) ||
+        uint64_t(local_now_us) - captured_us > 5'000'000)
+      return {};
+    std::lock_guard lock(mutex_);
+    return {shared_from_this(), ++issued_id_,
+            now - std::chrono::microseconds(local_now_us - captured_us)};
+  }
+
+  void Record(const VideoLatencyFrame& frame, Clock::time_point now) {
+    std::lock_guard lock(mutex_);
+    // Redraws, cached snapshots and late completions must not count twice.
+    if (frame.id <= last_id_) return;
+    last_id_ = frame.id;
+    const double ms =
+        std::chrono::duration<double, std::milli>(now - frame.capture_time)
+            .count();
+    if (ms < 0 || ms > 5000) return;
+    samples_.push_back({now, ms});
+    Prune(now);
+  }
+
+  std::optional<Snapshot> Get(Clock::time_point now = Clock::now()) {
+    std::lock_guard lock(mutex_);
+    Prune(now);
+    if (samples_.empty()) return std::nullopt;
+    double sum = 0;
+    for (const auto& sample : samples_) {
+      sum += sample.ms;
+    }
+    return Snapshot{sum / samples_.size(), samples_.size()};
+  }
+
+  void Reset() {
+    std::lock_guard lock(mutex_);
+    samples_.clear();
+    last_id_ = issued_id_;  // Invalidate frames still held by a renderer.
+  }
+
+ private:
+  void Prune(Clock::time_point now) {
+    while (!samples_.empty() &&
+           (now - samples_.front().time > std::chrono::seconds(1) ||
+            samples_.size() > 240))
+      samples_.pop_front();
+  }
+  struct Sample {
+    Clock::time_point time;
+    double ms;
+  };
+  std::mutex mutex_;
+  uint64_t issued_id_ = 0;
+  uint64_t last_id_ = 0;
+  std::deque<Sample> samples_;
+};
+
+inline void VideoLatencyFrame::MarkSubmitted(Clock::time_point now) const {
+  MarkPresented(now);
+}
+
+inline void VideoLatencyFrame::MarkPresented(Clock::time_point now) const {
+  if (stats) stats->Record(*this, now);
+}
+}  // namespace crossdesk
+
+#endif

apps/desktop/src/gui/runtime/connection_latency.h

@@ -0,0 +1,59 @@
+/*
+ * @Author: DI JUNKUN
+ * @Date: 2026-09-26
+ * Copyright (c) 2026 by DI JUNKUN, All Rights Reserved.
+ */
+
+#ifndef _CONNECTION_LATENCY_H_
+#define _CONNECTION_LATENCY_H_
+
+#include <chrono>
+#include <cmath>
+#include <mutex>
+#include <optional>
+
+namespace crossdesk::gui_detail {
+
+// Presentation-only smoothing. The transport's raw RTT remains available for
+// recovery, congestion control and diagnostics. A missing one-second report
+// does not flicker, but a disconnected/stalled peer cannot leave a stale value.
+class ConnectionLatencyStats {
+ public:
+  using Clock = std::chrono::steady_clock;
+
+  void Update(double rtt_ms, Clock::time_point now = Clock::now()) {
+    if (!std::isfinite(rtt_ms) || rtt_ms < 0 || rtt_ms > 2000) return;
+    std::lock_guard lock(mutex_);
+    if (average_ms_ && now < updated_) return;
+    if (!Fresh(now)) {
+      average_ms_ = rtt_ms;
+    } else {
+      *average_ms_ += 0.25 * (rtt_ms - *average_ms_);
+    }
+    updated_ = now;
+  }
+
+  std::optional<double> Get(Clock::time_point now = Clock::now()) const {
+    std::lock_guard lock(mutex_);
+    return Fresh(now) ? average_ms_ : std::nullopt;
+  }
+
+  void Reset() {
+    std::lock_guard lock(mutex_);
+    average_ms_.reset();
+  }
+
+ private:
+  bool Fresh(Clock::time_point now) const {
+    // The UI may snapshot `now` just before the report thread updates us.
+    // A newer valid report must not cause a one-frame unavailable flicker.
+    return average_ms_ && now - updated_ < std::chrono::seconds(3);
+  }
+  mutable std::mutex mutex_;
+  std::optional<double> average_ms_;
+  Clock::time_point updated_{};
+};
+
+}  // namespace crossdesk::gui_detail
+
+#endif

apps/desktop/src/gui/runtime/connection_runtime.cpp

@@ -417,8 +417,11 @@ void GuiRuntime::WaitForSessionCleanup() {
 
 void GuiRuntime::ResetRemoteSessionResources(
     std::shared_ptr<RemoteSession> props) {
+  props->net_traffic_stats_.Reset();
   {
     std::lock_guard<std::mutex> lock(props->video_frame_mutex_);
+    props->video_latency_->Reset();
+    props->video_frame_timing_ = {};
     props->front_frame_.reset();
     props->back_frame_.reset();
     props->thumbnail_frame_.reset();

apps/desktop/src/gui/runtime/net_traffic_stats_cache.h

@@ -0,0 +1,122 @@
+/*
+ * @Author: DI JUNKUN
+ * @Date: 2026-09-26
+ * Copyright (c) 2026 by DI JUNKUN, All Rights Reserved.
+ */
+
+#ifndef _NET_TRAFFIC_STATS_CACHE_H_
+#define _NET_TRAFFIC_STATS_CACHE_H_
+
+#include <atomic>
+
+#include "minirtc.h"
+#include "runtime/connection_latency.h"
+
+namespace crossdesk::gui_detail {
+
+// Fields are independent observations and may come from different reports.
+// Relaxed accesses keep each field safe without publishing any other state.
+class NetTrafficStatsCache {
+  static_assert(std::atomic<uint32_t>::is_always_lock_free &&
+                    std::atomic<float>::is_always_lock_free &&
+                    std::atomic<double>::is_always_lock_free &&
+                    std::atomic<bool>::is_always_lock_free,
+                "Network statistics require lock-free scalar atomics");
+
+ public:
+  void Store(const MiniRtcNetTrafficStats& stats) {
+    video_inbound_stats_.Store(stats.video_inbound_stats);
+    video_outbound_stats_.Store(stats.video_outbound_stats);
+    audio_inbound_stats_.Store(stats.audio_inbound_stats);
+    audio_outbound_stats_.Store(stats.audio_outbound_stats);
+    data_inbound_stats_.Store(stats.data_inbound_stats);
+    data_outbound_stats_.Store(stats.data_outbound_stats);
+    total_inbound_stats_.Store(stats.total_inbound_stats);
+    total_outbound_stats_.Store(stats.total_outbound_stats);
+    srtp_active_.store(stats.srtp_active, std::memory_order_relaxed);
+    rtt_ms_.store(stats.rtt_ms, std::memory_order_relaxed);
+    connection_latency_.Update(stats.rtt_ms);
+  }
+
+  MiniRtcNetTrafficStats Load() const {
+    MiniRtcNetTrafficStats stats{};
+    stats.video_inbound_stats = video_inbound_stats_.Load();
+    stats.video_outbound_stats = video_outbound_stats_.Load();
+    stats.audio_inbound_stats = audio_inbound_stats_.Load();
+    stats.audio_outbound_stats = audio_outbound_stats_.Load();
+    stats.data_inbound_stats = data_inbound_stats_.Load();
+    stats.data_outbound_stats = data_outbound_stats_.Load();
+    stats.total_inbound_stats = total_inbound_stats_.Load();
+    stats.total_outbound_stats = total_outbound_stats_.Load();
+    stats.srtp_active = srtp_active_.load(std::memory_order_relaxed);
+    stats.rtt_ms = rtt_ms_.load(std::memory_order_relaxed);
+    return stats;
+  }
+
+  uint32_t DataOutboundBitrate() const {
+    return data_outbound_stats_.bitrate.load(std::memory_order_relaxed);
+  }
+
+  std::optional<double> SmoothedRttMs(
+      ConnectionLatencyStats::Clock::time_point now =
+          ConnectionLatencyStats::Clock::now()) const {
+    return connection_latency_.Get(now);
+  }
+
+  void ResetLatency() { connection_latency_.Reset(); }
+
+  void Reset() {
+    Store(MiniRtcNetTrafficStats{});
+    ResetLatency();
+  }
+
+ private:
+  struct InboundStats {
+    void Store(const MiniRtcInboundStats& stats) {
+      bitrate.store(stats.bitrate, std::memory_order_relaxed);
+      rtp_packet_count.store(stats.rtp_packet_count, std::memory_order_relaxed);
+      loss_rate.store(stats.loss_rate, std::memory_order_relaxed);
+    }
+
+    MiniRtcInboundStats Load() const {
+      return {bitrate.load(std::memory_order_relaxed),
+              rtp_packet_count.load(std::memory_order_relaxed),
+              loss_rate.load(std::memory_order_relaxed)};
+    }
+
+    std::atomic<uint32_t> bitrate{0};
+    std::atomic<uint32_t> rtp_packet_count{0};
+    std::atomic<float> loss_rate{0};
+  };
+
+  struct OutboundStats {
+    void Store(const MiniRtcOutboundStats& stats) {
+      bitrate.store(stats.bitrate, std::memory_order_relaxed);
+      rtp_packet_count.store(stats.rtp_packet_count, std::memory_order_relaxed);
+    }
+
+    MiniRtcOutboundStats Load() const {
+      return {bitrate.load(std::memory_order_relaxed),
+              rtp_packet_count.load(std::memory_order_relaxed)};
+    }
+
+    std::atomic<uint32_t> bitrate{0};
+    std::atomic<uint32_t> rtp_packet_count{0};
+  };
+
+  InboundStats video_inbound_stats_;
+  OutboundStats video_outbound_stats_;
+  InboundStats audio_inbound_stats_;
+  OutboundStats audio_outbound_stats_;
+  InboundStats data_inbound_stats_;
+  OutboundStats data_outbound_stats_;
+  InboundStats total_inbound_stats_;
+  OutboundStats total_outbound_stats_;
+  std::atomic<bool> srtp_active_{false};
+  std::atomic<double> rtt_ms_{-1};
+  ConnectionLatencyStats connection_latency_;
+};
+
+}  // namespace crossdesk::gui_detail
+
+#endif

apps/desktop/src/gui/runtime/peer_data_callbacks.cpp

@@ -294,7 +294,7 @@ void PeerEventHandler::OnReceiveDataBuffer(
       props->remote_cursor_state_received_ = true;
       props->cursor_presentation_.Observe(merged, SDL_GetTicks());
       if (changed) {
-        LOG_INFO("Received cursor state: seq={}, visible={}, shape={}, "
+        LOG_DEBUG("Received cursor state: seq={}, visible={}, shape={}, "
                  "mode={}, reason={}",
                  remote_action.cs.seq, remote_action.cs.visible,
                  static_cast<int>(remote_action.cs.shape),

apps/desktop/src/gui/runtime/peer_event_handler.cpp

@@ -300,6 +300,7 @@ void PeerEventHandler::OnConnectionStatus(ConnectionStatus status,
         runtime->keyboard_.ReleaseRemotePressedKeys(remote_id,
                                                     "connection_closed");
         props->connection_established_ = false;
+        props->net_traffic_stats_.Reset();
         props->enable_mouse_control_ = false;
         runtime->ResetRemoteServiceStatus(*props);
         {
@@ -336,6 +337,8 @@ void PeerEventHandler::OnConnectionStatus(ConnectionStatus status,
         }
         {
           std::lock_guard<std::mutex> lock(props->video_frame_mutex_);
+          props->video_latency_->Reset();
+          props->video_frame_timing_ = {};
           props->front_frame_.reset();
           props->back_frame_.reset();
           if (native_snapshot &&
@@ -508,6 +511,7 @@ void PeerEventHandler::OnNetStatusReport(
   auto props = runtime->FindRemoteSession(remote_id);
   if (!props) return;
   if (props->traversal_mode_ != mode) {
+    props->net_traffic_stats_.ResetLatency();
     props->traversal_mode_ = mode;
     LOG_INFO("Net mode: [{}]", int(props->traversal_mode_));
   }
@@ -518,7 +522,7 @@ void PeerEventHandler::OnNetStatusReport(
 
   // only display client side net status if connected to itself
   if (!(runtime->peer_reserved_ && !strstr(client_id, "C-"))) {
-    props->net_traffic_stats_ = *net_traffic_stats;
+    props->net_traffic_stats_.Store(*net_traffic_stats);
   }
 }
 }  // namespace crossdesk

apps/desktop/src/gui/runtime/peer_media_callbacks.cpp

@@ -36,7 +36,7 @@ void PeerEventHandler::OnReceiveVideoBuffer(
   auto callback = handler->EnterCallback();
   if (!callback) return;
   GuiRuntime* runtime = handler ? &handler->owner_ : nullptr;
-  if (!runtime) {
+  if (!runtime || !video_frame) {
     return;
   }
 
@@ -45,13 +45,18 @@ void PeerEventHandler::OnReceiveVideoBuffer(
   if (!props) return;
 
   if (props->connection_established_) {
+    const auto timing_now = VideoLatencyFrame::Clock::now();
+    const auto timing = props->video_latency_->Frame(
+        video_frame->captured_timestamp, GetSystemTimeMicros(props->peer_),
+        timing_now);
     bool background_snapshot_only = false;
     auto* native_renderer = runtime->video_renderer_.get();
     if (native_renderer && native_renderer->IsActive()) {
       VideoRenderer::SubmitResult submit_result =
           VideoRenderer::SubmitResult::failed;
       if (const auto* native = GetNativeVideoFrame(video_frame)) {
-        submit_result = native_renderer->SubmitNativeFrame(remote_id, *native);
+        submit_result =
+            native_renderer->SubmitNativeFrame(remote_id, *native, timing);
         // A CPU NV12 native frame is valid MiniRTC input, but the macOS Metal
         // fast path only accepts CVPixelBuffer. Materialize it when that path
         // rejects a software decoder's descriptor. This also supports peers
@@ -69,14 +74,14 @@ void PeerEventHandler::OnReceiveVideoBuffer(
             submit_result = native_renderer->SubmitNv12(
                 remote_id, fallback.data(), fallback.size(),
                 static_cast<int>(native->width),
-                static_cast<int>(native->height));
+                static_cast<int>(native->height), timing);
           }
         }
       } else
       {
         submit_result = native_renderer->SubmitNv12(
             remote_id, reinterpret_cast<const uint8_t*>(video_frame->data),
-            video_frame->size, video_frame->width, video_frame->height);
+            video_frame->size, video_frame->width, video_frame->height, timing);
       }
       if (submit_result == VideoRenderer::SubmitResult::submitted) {
         std::lock_guard<std::mutex> lock(props->video_frame_mutex_);
@@ -170,6 +175,7 @@ void PeerEventHandler::OnReceiveVideoBuffer(
       props->video_size_ = frame_size;
 
       props->front_frame_.swap(props->back_frame_);
+      props->video_frame_timing_ = timing;
       props->thumbnail_frame_ = props->front_frame_;
       props->thumbnail_width_ = video_frame->width;
       props->thumbnail_height_ = video_frame->height;

apps/desktop/src/gui/runtime/remote_session.h

@@ -14,6 +14,7 @@
 #include <filesystem>
 #include <memory>
 #include <mutex>
+#include <optional>
 #include <queue>
 #include <string>
 #include <vector>
@@ -23,6 +24,8 @@
 #include "display_info.h"
 #include "cursor_presentation.h"
 #include "minirtc.h"
+#include "rendering/video_latency.h"
+#include "runtime/net_traffic_stats_cache.h"
 
 namespace crossdesk { class PeerEventHandler; }
 
@@ -115,6 +118,9 @@ struct RemoteSession {
   int selected_display_ = 0;
   size_t video_size_ = 0;
   uint64_t video_frame_sequence_ = 0;
+  VideoLatencyFrame video_frame_timing_;
+  std::shared_ptr<VideoLatencyStats> video_latency_ =
+      std::make_shared<VideoLatencyStats>();
   bool tab_selected_ = false;
   bool tab_opened_ = true;
   std::string remote_host_name_;
@@ -150,7 +156,9 @@ struct RemoteSession {
   int fps_ = 0;
   int frame_count_ = 0;
   std::chrono::steady_clock::time_point last_time_;
-  MiniRtcNetTrafficStats net_traffic_stats_{};
+  // UI-thread snapshot refreshed with FPS once per second.
+  std::optional<VideoLatencyStats::Snapshot> video_latency_snapshot_;
+  NetTrafficStatsCache net_traffic_stats_;
 
   using QueuedFile = FileTransferState::QueuedFile;
   using FileTransferStatus = FileTransferState::FileTransferStatus;

apps/desktop/src/gui/ui/stream_window.slint

@@ -56,6 +56,8 @@ export global StreamStrings {
     in-out property <string> stats-out: "Out";
     in-out property <string> stats-loss-rate: "Loss Rate";
     in-out property <string> stats-resolution: "Res";
+    in-out property <string> stats-video-latency: "Video delay";
+    in-out property <string> stats-connection-latency: "Connection RTT";
     in-out property <string> stats-connection-mode: "Mode";
     in-out property <string> stats-encryption: "Encryption";
     in-out property <string> stats-encryption-enabled: "Enabled";
@@ -218,6 +220,8 @@ export component StreamWindow inherits Window {
     in property <[NetworkStatsRow]> stats-rows;
     in property <string> stats-fps: "0";
     in property <string> stats-resolution: "";
+    in property <string> stats-video-latency: "—";
+    in property <string> stats-connection-latency: "—";
     in property <string> stats-connection-mode: "";
     in property <bool> stats-encryption-enabled: false;
     in property <bool> file-transfer-visible: false;
@@ -253,7 +257,7 @@ export component StreamWindow inherits Window {
     private property <length> stats-row-height: 18px;
     private property <length> stats-header-height: 18px;
     private property <length> stats-content-height:
-        root.stats-header-height + root.stats-rows.length * root.stats-row-height + 44px;
+        root.stats-header-height + root.stats-rows.length * root.stats-row-height + 65px;
     private property <bool> display-menu-open: false;
     private property <bool> display-menu-animation-enabled: false;
     private property <float> display-menu-progress: 0.0;
@@ -903,18 +907,22 @@ export component StreamWindow inherits Window {
                     private property <length> details-right-width:
                         right-label-width-probe.preferred-width + 6px
                             + max(resolution-width-probe.preferred-width,
+                                connection-latency-width-probe.preferred-width,
                                 encryption-width-probe.preferred-width
                                     + (root.stats-encryption-enabled ? 14px : 0px));
-                    private property <length> details-right-x: self.width / 2;
+                    private property <length> details-right-x:
+                        min(self.width / 2, self.width - self.details-right-width - 6px);
 
                     left-label-width-probe := Text {
                         visible: false;
-                        text: "FPS\n" + StreamStrings.stats-connection-mode;
+                        text: "FPS\n" + StreamStrings.stats-video-latency
+                            + "\n" + StreamStrings.stats-connection-mode;
                         font-size: ImGuiFontStyle.small;
                     }
                     right-label-width-probe := Text {
                         visible: false;
-                        text: StreamStrings.stats-resolution + "\n" + StreamStrings.stats-encryption;
+                        text: StreamStrings.stats-resolution + "\n" + StreamStrings.stats-connection-latency
+                            + "\n" + StreamStrings.stats-encryption;
                         font-size: ImGuiFontStyle.small;
                     }
                     resolution-width-probe := Text {
@@ -923,6 +931,12 @@ export component StreamWindow inherits Window {
                         font-size: ImGuiFontStyle.body;
                         font-weight: 600;
                     }
+                    connection-latency-width-probe := Text {
+                        visible: false;
+                        text: root.stats-connection-latency;
+                        font-size: ImGuiFontStyle.body;
+                        font-weight: 600;
+                    }
                     encryption-width-probe := Text {
                         visible: false;
                         text: root.stats-encryption-enabled
@@ -1029,12 +1043,14 @@ export component StreamWindow inherits Window {
                     for metric[index] in [
                         { label: "FPS", value: root.stats-fps },
                         { label: StreamStrings.stats-resolution, value: root.stats-resolution },
+                        { label: StreamStrings.stats-video-latency, value: root.stats-video-latency },
+                        { label: StreamStrings.stats-connection-latency, value: root.stats-connection-latency },
                         { label: StreamStrings.stats-connection-mode, value: root.stats-connection-mode },
                         { label: StreamStrings.stats-encryption, value: root.stats-encryption-enabled
                             ? StreamStrings.stats-encryption-enabled : StreamStrings.stats-encryption-disabled },
                     ]: Rectangle {
                         private property <length> encryption-icon-width:
-                            index == 3 && root.stats-encryption-enabled ? 14px : 0px;
+                            index == 5 && root.stats-encryption-enabled ? 14px : 0px;
                         x: mod(index, 2) == 1 ? stats-table.details-right-x : 6px;
                         y: root.stats-header-height + root.stats-rows.length * stats-table.row-height
                             + 2px + floor(index / 2) * 21px;
@@ -1058,14 +1074,14 @@ export component StreamWindow inherits Window {
                             height: parent.height;
                             width: parent.width - self.x - parent.encryption-icon-width;
                             text: metric.value;
-                            color: index == 3 && root.stats-encryption-enabled ? #18794e : #253247;
+                            color: index == 5 && root.stats-encryption-enabled ? #18794e : #253247;
                             font-size: ImGuiFontStyle.body;
                             font-weight: 600;
                             horizontal-alignment: left;
                             vertical-alignment: center;
                             overflow: elide;
                         }
-                        if index == 3 && root.stats-encryption-enabled: Text {
+                        if index == 5 && root.stats-encryption-enabled: Text {
                             x: metric-value.x + min(metric-value.preferred-width, metric-value.width) + 4px;
                             y: metric-value.y + (metric-value.height - self.height) / 2;
                             width: 10px;

apps/desktop/src/gui/ui/ui_localization.h

@@ -175,6 +175,8 @@ inline int ApplyStreamWindowStrings(
   strings.set_stats_out(Text(localization::out[language]));
   strings.set_stats_loss_rate(Text(localization::loss_rate[language]));
   strings.set_stats_resolution(Text(localization::resolution[language]));
+  strings.set_stats_video_latency(Text(localization::video_latency[language]));
+  strings.set_stats_connection_latency(Text(localization::connection_latency[language]));
   strings.set_stats_connection_mode(
       Text(localization::connection_mode[language]));
   strings.set_stats_encryption(

apps/desktop/src/log/rd_log.cpp

@@ -1,11 +1,7 @@
 #include "rd_log.h"
 
-#include <chrono>
-#include <ctime>
 #include <filesystem>
-#include <iomanip>
 #include <mutex>
-#include <sstream>
 #include <vector>
 
 #include "spdlog/sinks/rotating_file_sink.h"
@@ -16,6 +12,7 @@ namespace crossdesk {
 namespace {
 
 std::string g_log_dir = "logs";
+std::string g_logger_name = LOGGER_NAME;
 std::once_flag g_logger_once_flag;
 std::mutex g_logger_mutex;
 std::shared_ptr<spdlog::logger> g_logger;
@@ -29,20 +26,20 @@ std::string NormalizeLogDirectory(const std::string& log_dir) {
 
 }  // namespace
 
-void InitLogger(const std::string& log_dir) {
+void InitLogger(const std::string& log_dir, const std::string& logger_name) {
   const auto directory = NormalizeLogDirectory(log_dir);
   std::lock_guard<std::mutex> lock(g_logger_mutex);
   if (g_logger) {
-    if (directory != g_log_dir) {
+    if (directory != g_log_dir || logger_name != g_logger_name) {
       g_logger->warn(
-          "InitLogger called after logger initialized. Ignoring log_dir: {}, "
-          "using previous log_dir: {}",
-          directory, g_log_dir);
+          "InitLogger called after logger initialized. Keeping logger {} in {}",
+          g_logger_name, g_log_dir);
     }
     return;
   }
 
   g_log_dir = directory;
+  g_logger_name = logger_name;
 }
 
 std::shared_ptr<spdlog::logger> get_logger() {
@@ -53,32 +50,23 @@ std::shared_ptr<spdlog::logger> get_logger() {
     std::error_code ec;
     std::filesystem::create_directories(g_log_dir, ec);
 
-    auto now = std::chrono::system_clock::now() + std::chrono::hours(8);
-    auto now_time = std::chrono::system_clock::to_time_t(now);
-
-    std::tm tm_info;
-#ifdef _WIN32
-    gmtime_s(&tm_info, &now_time);
-#else
-    gmtime_r(&now_time, &tm_info);
-#endif
-
-    std::stringstream ss;
-    ss << LOGGER_NAME;
-    ss << std::put_time(&tm_info, "-%Y%m%d-%H%M%S.log");
-
-    std::string filename = g_log_dir + "/" + ss.str();
+    // Reuse the same rotation set across restarts. Timestamped base names
+    // give each launch its own backups and let the directory grow forever.
+    auto file_sink = std::make_shared<spdlog::sinks::rotating_file_sink_mt>(
+        g_log_dir + "/" + g_logger_name + ".log", 5 * 1024 * 1024, 3);
 
     std::vector<spdlog::sink_ptr> sinks;
     sinks.push_back(std::make_shared<spdlog::sinks::stdout_color_sink_mt>());
-    sinks.push_back(std::make_shared<spdlog::sinks::rotating_file_sink_mt>(
-        filename, 5 * 1024 * 1024, 3));
+    sinks.push_back(file_sink);
 
-    auto logger = std::make_shared<spdlog::logger>(LOGGER_NAME, sinks.begin(),
+    auto logger = std::make_shared<spdlog::logger>(g_logger_name, sinks.begin(),
                                                    sinks.end());
+    logger->set_level(SPDLOG_ACTIVE_LEVEL <= SPDLOG_LEVEL_DEBUG
+                          ? spdlog::level::debug
+                          : spdlog::level::info);
     logger->flush_on(spdlog::level::info);
     spdlog::register_logger(logger);
-    logger->info("Logger initialized: path={}", filename);
+    logger->info("Logger initialized: path={}", file_sink->filename());
     g_logger = std::move(logger);
   });
 

apps/desktop/src/log/rd_log.h

@@ -10,21 +10,26 @@
 #include <memory>
 #include <string>
 
-#include "spdlog/spdlog.h"
-
+#ifndef SPDLOG_ACTIVE_LEVEL
 #define SPDLOG_ACTIVE_LEVEL SPDLOG_LEVEL_INFO
+#endif
+
+#include "spdlog/spdlog.h"
 
 namespace crossdesk {
 
 constexpr auto LOGGER_NAME = "crossdesk";
 
-void InitLogger(const std::string& log_dir);
+void InitLogger(const std::string& log_dir,
+                const std::string& logger_name = LOGGER_NAME);
 
 std::shared_ptr<spdlog::logger> get_logger();
 
+#define LOG_TRACE(...) SPDLOG_LOGGER_TRACE(get_logger(), __VA_ARGS__)
+#define LOG_DEBUG(...) SPDLOG_LOGGER_DEBUG(get_logger(), __VA_ARGS__)
 #define LOG_INFO(...) SPDLOG_LOGGER_INFO(get_logger(), __VA_ARGS__)
 #define LOG_WARN(...) SPDLOG_LOGGER_WARN(get_logger(), __VA_ARGS__)
 #define LOG_ERROR(...) SPDLOG_LOGGER_ERROR(get_logger(), __VA_ARGS__)
 #define LOG_FATAL(...) SPDLOG_LOGGER_CRITICAL(get_logger(), __VA_ARGS__)
 }  // namespace crossdesk
-#endif
+#endif

apps/desktop/src/platform/common/gui/opengl_video_renderer.cpp

@@ -59,6 +59,7 @@ struct FrameSlot {
   int height = 0;
   std::string remote_id;
   uint64_t sequence = 0;
+  VideoLatencyFrame timing;
   SlotUse use = SlotUse::available;
   bool valid = false;
 };
@@ -320,6 +321,7 @@ struct OpenGlVideoRenderer::Impl {
   bool unpack_subimage_available = false;
   std::string uploaded_stream;
   uint64_t uploaded_sequence = 0;
+  VideoLatencyFrame uploaded_timing;
 
 #if CROSSDESK_OPENGL_CUDA_INTEROP
   enum class CudaUploadResult {
@@ -1023,25 +1025,22 @@ void OpenGlVideoRenderer::DiscardStream(std::string_view remote_id) {
   }
 }
 
-OpenGlVideoRenderer::SubmitResult
-OpenGlVideoRenderer::SubmitNv12(std::string_view remote_id,
-                                       const uint8_t *data, size_t size,
-                                       int width, int height) {
-  return SubmitNv12Internal(remote_id, data, size, width, height, true);
+OpenGlVideoRenderer::SubmitResult OpenGlVideoRenderer::SubmitNv12(
+    std::string_view remote_id, const uint8_t *data, size_t size, int width,
+    int height, VideoLatencyFrame timing) {
+  return SubmitNv12Internal(remote_id, data, size, width, height, true, timing);
 }
 
-OpenGlVideoRenderer::SubmitResult
-OpenGlVideoRenderer::SubmitCachedNv12(std::string_view remote_id,
-                                             const uint8_t *data, size_t size,
-                                             int width, int height) {
-  return SubmitNv12Internal(remote_id, data, size, width, height, false);
+OpenGlVideoRenderer::SubmitResult OpenGlVideoRenderer::SubmitCachedNv12(
+    std::string_view remote_id, const uint8_t *data, size_t size, int width,
+    int height, VideoLatencyFrame timing) {
+  return SubmitNv12Internal(remote_id, data, size, width, height, false,
+                            timing);
 }
 
-OpenGlVideoRenderer::SubmitResult
-OpenGlVideoRenderer::SubmitNv12Internal(std::string_view remote_id,
-                                               const uint8_t *data, size_t size,
-                                               int width, int height,
-                                               bool replace_pending) {
+OpenGlVideoRenderer::SubmitResult OpenGlVideoRenderer::SubmitNv12Internal(
+    std::string_view remote_id, const uint8_t *data, size_t size, int width,
+    int height, bool replace_pending, VideoLatencyFrame timing) {
   if (!IsReady()) {
     return SubmitResult::failed;
   }
@@ -1104,14 +1103,15 @@ OpenGlVideoRenderer::SubmitNv12Internal(std::string_view remote_id,
   target->height = height;
   target->remote_id.assign(remote_id);
   target->sequence = frames.next_sequence++;
+  target->timing = timing;
   target->use = SlotUse::pending;
   target->valid = true;
   return SubmitResult::submitted;
 }
 
-OpenGlVideoRenderer::SubmitResult
-OpenGlVideoRenderer::SubmitNativeFrame(std::string_view remote_id,
-                                       const MiniRtcNativeVideoFrame &frame) {
+OpenGlVideoRenderer::SubmitResult OpenGlVideoRenderer::SubmitNativeFrame(
+    std::string_view remote_id, const MiniRtcNativeVideoFrame &frame,
+    VideoLatencyFrame timing) {
   if (!IsReady()) {
     return SubmitResult::failed;
   }
@@ -1183,6 +1183,7 @@ OpenGlVideoRenderer::SubmitNativeFrame(std::string_view remote_id,
   target->height = static_cast<int>(native->height);
   target->remote_id.assign(remote_id);
   target->sequence = frames.next_sequence++;
+  target->timing = timing;
   target->use = SlotUse::pending;
   target->valid = true;
   return SubmitResult::submitted;
@@ -1204,6 +1205,7 @@ OpenGlVideoRenderer::RenderLatest(std::string_view remote_id,
   const unsigned char *y_data = nullptr;
   const unsigned char *uv_data = nullptr;
   NativeVideoFrameRef active_native_frame;
+  VideoLatencyFrame timing;
   {
     std::lock_guard lock(impl_->frames->mutex);
     for (size_t index = 0; index < impl_->frames->slots.size(); ++index) {
@@ -1221,6 +1223,7 @@ OpenGlVideoRenderer::RenderLatest(std::string_view remote_id,
       source_width = selected.width;
       source_height = selected.height;
       active_native_frame = selected.native_frame;
+      timing = selected.timing;
       if (!selected.bytes.empty()) {
         const size_t y_size = static_cast<size_t>(source_width) * source_height;
         y_data = selected.bytes.data();
@@ -1421,6 +1424,7 @@ OpenGlVideoRenderer::RenderLatest(std::string_view remote_id,
         impl_->texture_height = source_height;
         impl_->uploaded_stream.assign(remote_id);
         impl_->uploaded_sequence = sequence;
+        impl_->uploaded_timing = timing;
         if (!use_pixel_unpack_buffer) {
           impl_->cpu_texture_width = source_width;
           impl_->cpu_texture_height = source_height;
@@ -1549,6 +1553,8 @@ OpenGlVideoRenderer::RenderLatest(std::string_view remote_id,
   }
 #endif
   const GLenum draw_error = glGetError();
+  if (has_video && draw_error == GL_NO_ERROR)
+    impl_->uploaded_timing.MarkSubmitted();
   RenderOutcome outcome{
       !upload_succeeded || draw_error != GL_NO_ERROR
           ? RenderResult::failed

apps/desktop/src/platform/common/gui/opengl_video_renderer.h

@@ -39,11 +39,14 @@ public:
 
   // Thread-safe; called from MiniRTC's decode callback thread.
   SubmitResult SubmitNv12(std::string_view remote_id, const uint8_t *data,
-                          size_t size, int width, int height) override;
+                          size_t size, int width, int height,
+                          VideoLatencyFrame timing = {}) override;
   SubmitResult SubmitCachedNv12(std::string_view remote_id, const uint8_t *data,
-                                size_t size, int width, int height) override;
+                                size_t size, int width, int height,
+                                VideoLatencyFrame timing = {}) override;
   SubmitResult SubmitNativeFrame(std::string_view remote_id,
-                                 const MiniRtcNativeVideoFrame &frame) override;
+                                 const MiniRtcNativeVideoFrame &frame,
+                                 VideoLatencyFrame timing = {}) override;
 
   // Draws below Slint while its OpenGL context is current. All dimensions are
   // physical pixels in the window client area. corner_radius_pixels clips the
@@ -61,7 +64,8 @@ public:
 private:
   SubmitResult SubmitNv12Internal(std::string_view remote_id,
                                   const uint8_t *data, size_t size, int width,
-                                  int height, bool replace_pending);
+                                  int height, bool replace_pending,
+                                  VideoLatencyFrame timing);
 
   struct Impl;
   std::unique_ptr<Impl> impl_;

apps/desktop/src/platform/common/posix_single_instance.cpp

@@ -0,0 +1,68 @@
+#include "platform/single_instance.h"
+
+#include <cerrno>
+#include <cstring>
+#include <fcntl.h>
+#include <sys/file.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include <utility>
+
+namespace crossdesk::platform {
+
+SingleInstanceGuard::SingleInstanceGuard(std::string application)
+    : application_(std::move(application)) {}
+
+SingleInstanceGuard::~SingleInstanceGuard() { Release(); }
+
+InstanceResult SingleInstanceGuard::TryAcquire(InstanceRole role,
+                                               std::string& error) {
+  error.clear();
+  if (handle_ != -1) return InstanceResult::kAcquired;
+  if (!ValidInstanceApplication(application_)) {
+    error = "Invalid single-instance application name";
+    return InstanceResult::kError;
+  }
+  // A fixed local path also coordinates launches with different TMPDIR/XDG
+  // settings. O_CLOEXEC prevents unrelated desktop/helper processes retaining it.
+  const std::string path = "/tmp/" + application_ + "-" +
+                           std::to_string(geteuid()) + "-" +
+                           InstanceRoleName(role) + ".lock";
+  const int fd = open(path.c_str(), O_CREAT | O_RDWR | O_CLOEXEC | O_NOFOLLOW, 0600);
+  if (fd < 0) {
+    error = "Cannot open single-instance lock: " + std::string(std::strerror(errno));
+    return InstanceResult::kError;
+  }
+  struct stat info {};
+  if (fstat(fd, &info) != 0 || !S_ISREG(info.st_mode) || info.st_uid != geteuid()) {
+    close(fd);
+    error = "Single-instance lock is not a regular file owned by this user";
+    return InstanceResult::kError;
+  }
+  int result;
+  do {
+    result = flock(fd, LOCK_EX | LOCK_NB);
+  } while (result != 0 && errno == EINTR);
+  if (result == 0) {
+    handle_ = fd;
+    return InstanceResult::kAcquired;
+  }
+  const int lock_error = errno;
+  close(fd);
+  if (lock_error == EWOULDBLOCK || lock_error == EAGAIN)
+    return InstanceResult::kAlreadyRunning;
+  error = "Cannot acquire single-instance lock: " +
+          std::string(std::strerror(lock_error));
+  return InstanceResult::kError;
+}
+
+void SingleInstanceGuard::Release() {
+  if (handle_ == -1) return;
+  // Close rather than LOCK_UN: a forked headless application may still own the
+  // same open file description. Never unlink a lock that another launch opened.
+  close(static_cast<int>(handle_));
+  handle_ = -1;
+}
+
+}  // namespace crossdesk::platform

apps/desktop/src/platform/linux/headless/headless_console.cpp

@@ -78,7 +78,7 @@ bool HeadlessConsole::Enable(const std::filesystem::path& log_directory,
   error_ = err;
   interactive_ = isatty(STDIN_FILENO) && isatty(output_);
   // Initialize after redirecting output so even the logger's first message
-  // stays in its original crossdesk-YYYYMMDD-HHMMSS.log file.
+  // stays in crossdesk.log.
   try {
     InitLogger(log_directory.string());
     for (const auto& sink : get_logger()->sinks()) {

apps/desktop/src/platform/macos/gui/metal_video_renderer.h

@@ -35,18 +35,20 @@ class MacMetalVideoRenderer final : public VideoRenderer {
 
   // Copies one tightly packed NV12 frame into a free shared Metal slot.
   SubmitResult SubmitNv12(std::string_view remote_id, const uint8_t* data,
-                          size_t size, int width, int height) override;
+                          size_t size, int width, int height,
+                          VideoLatencyFrame timing = {}) override;
 
   // Retains an IOSurface-backed VideoToolbox CVPixelBuffer until the Metal
   // command buffer using it has completed.
   SubmitResult SubmitNativeFrame(std::string_view remote_id,
-                                 const MiniRtcNativeVideoFrame& frame) override;
+                                 const MiniRtcNativeVideoFrame& frame,
+                                 VideoLatencyFrame timing = {}) override;
 
   // Seeds a newly selected stream from its retained CPU snapshot without
   // replacing a newer decoded frame that is already queued or rendering.
-  SubmitResult SubmitCachedNv12(std::string_view remote_id,
-                                const uint8_t* data, size_t size, int width,
-                                int height) override;
+  SubmitResult SubmitCachedNv12(std::string_view remote_id, const uint8_t* data,
+                                size_t size, int width, int height,
+                                VideoLatencyFrame timing = {}) override;
 
   // Attaches a native CAMetalLayer-backed sibling below Slint's NSView and
   // restores the containing AppKit window's ordinary opaque titlebar.
@@ -76,7 +78,8 @@ class MacMetalVideoRenderer final : public VideoRenderer {
  private:
   SubmitResult SubmitNv12Internal(std::string_view remote_id,
                                   const uint8_t* data, size_t size, int width,
-                                  int height, bool replace_pending);
+                                  int height, bool replace_pending,
+                                  VideoLatencyFrame timing);
 
   struct Impl;
   std::unique_ptr<Impl> impl_;

apps/desktop/src/platform/macos/gui/metal_video_renderer.mm

@@ -3,11 +3,13 @@
 #import <AppKit/AppKit.h>
 #import <CoreVideo/CVMetalTextureCache.h>
 #import <Metal/Metal.h>
+#import <QuartzCore/CABase.h>
 #import <QuartzCore/CAMetalLayer.h>
 
 #include <algorithm>
 #include <array>
 #include <atomic>
+#include <cmath>
 #include <cstring>
 #include <limits>
 #include <mutex>
@@ -340,6 +342,7 @@ struct FrameSlot {
   int height = 0;
   std::string remote_id;
   uint64_t sequence = 0;
+  VideoLatencyFrame timing;
   SlotUse use = SlotUse::available;
   bool valid = false;
 
@@ -744,14 +747,16 @@ void MacMetalVideoRenderer::DiscardStream(std::string_view remote_id) {
   }
 }
 
-MacMetalVideoRenderer::SubmitResult MacMetalVideoRenderer::SubmitNv12(
-    std::string_view remote_id, const uint8_t* data, size_t size, int width,
-    int height) {
-  return SubmitNv12Internal(remote_id, data, size, width, height, true);
+MacMetalVideoRenderer::SubmitResult MacMetalVideoRenderer::SubmitNv12(std::string_view remote_id,
+                                                                      const uint8_t* data,
+                                                                      size_t size, int width,
+                                                                      int height,
+                                                                      VideoLatencyFrame timing) {
+  return SubmitNv12Internal(remote_id, data, size, width, height, true, timing);
 }
 
 MacMetalVideoRenderer::SubmitResult MacMetalVideoRenderer::SubmitNativeFrame(
-    std::string_view remote_id, const MiniRtcNativeVideoFrame& frame) {
+    std::string_view remote_id, const MiniRtcNativeVideoFrame& frame, VideoLatencyFrame timing) {
   if (!IsReady()) {
     return SubmitResult::failed;
   }
@@ -781,8 +786,7 @@ MacMetalVideoRenderer::SubmitResult MacMetalVideoRenderer::SubmitNativeFrame(
                              packed_nv12.size()) != 0) {
       return SubmitResult::failed;
     }
-    return SubmitNv12(remote_id, packed_nv12.data(), packed_nv12.size(), width,
-                      height);
+    return SubmitNv12(remote_id, packed_nv12.data(), packed_nv12.size(), width, height, timing);
   };
 
   CVPixelBufferRef pixel_buffer =
@@ -878,6 +882,7 @@ MacMetalVideoRenderer::SubmitResult MacMetalVideoRenderer::SubmitNativeFrame(
   target->height = height;
   target->remote_id.assign(remote_id);
   target->sequence = frames.next_sequence++;
+  target->timing = timing;
   target->use = SlotUse::pending;
   target->valid = true;
   if (!impl_->native_path_logged.exchange(true, std::memory_order_acq_rel)) {
@@ -887,14 +892,14 @@ MacMetalVideoRenderer::SubmitResult MacMetalVideoRenderer::SubmitNativeFrame(
 }
 
 MacMetalVideoRenderer::SubmitResult MacMetalVideoRenderer::SubmitCachedNv12(
-    std::string_view remote_id, const uint8_t* data, size_t size, int width,
-    int height) {
-  return SubmitNv12Internal(remote_id, data, size, width, height, false);
+    std::string_view remote_id, const uint8_t* data, size_t size, int width, int height,
+    VideoLatencyFrame timing) {
+  return SubmitNv12Internal(remote_id, data, size, width, height, false, timing);
 }
 
 MacMetalVideoRenderer::SubmitResult MacMetalVideoRenderer::SubmitNv12Internal(
-    std::string_view remote_id, const uint8_t* data, size_t size, int width,
-    int height, bool replace_pending) {
+    std::string_view remote_id, const uint8_t* data, size_t size, int width, int height,
+    bool replace_pending, VideoLatencyFrame timing) {
   if (!IsReady()) {
     return SubmitResult::failed;
   }
@@ -968,6 +973,7 @@ MacMetalVideoRenderer::SubmitResult MacMetalVideoRenderer::SubmitNv12Internal(
 
   target->remote_id.assign(remote_id);
   target->sequence = frames.next_sequence++;
+  target->timing = timing;
   target->use = SlotUse::pending;
   target->valid = true;
   return SubmitResult::submitted;
@@ -1189,6 +1195,7 @@ MacMetalVideoRenderer::RenderOutcome MacMetalVideoRenderer::RenderLatest(
 
     id<MTLTexture> y_texture = nil;
     id<MTLTexture> uv_texture = nil;
+    VideoLatencyFrame timing;
     {
       std::lock_guard lock(impl_->frames->mutex);
       auto& slot = impl_->frames->slots[slot_index];
@@ -1202,6 +1209,7 @@ MacMetalVideoRenderer::RenderOutcome MacMetalVideoRenderer::RenderLatest(
       slot.use = SlotUse::in_flight;
       y_texture = slot.y_texture;
       uv_texture = slot.uv_texture;
+      timing = slot.timing;
     }
 
     MTLRenderPassDescriptor* pass = [MTLRenderPassDescriptor renderPassDescriptor];
@@ -1259,6 +1267,19 @@ MacMetalVideoRenderer::RenderOutcome MacMetalVideoRenderer::RenderLatest(
         slot.use = SlotUse::available;
       }
     }];
+    [drawable addPresentedHandler:^(id<MTLDrawable> presented) {
+      // presentedTime uses the Core Animation host clock. Translate its age
+      // into our steady clock, excluding callback scheduling delay. Capturing
+      // timing by value keeps this safe after a session/renderer is destroyed.
+      const double presented_time = presented.presentedTime;
+      const auto now = VideoLatencyFrame::Clock::now();
+      const double age = CACurrentMediaTime() - presented_time;
+      if (presented_time > 0 && std::isfinite(age) && age >= 0 && age <= 5) {
+        timing.MarkPresented(
+            now - std::chrono::duration_cast<VideoLatencyFrame::Clock::duration>(
+                      std::chrono::duration<double>(age)));
+      }
+    }];
     [command_buffer presentDrawable:drawable];
     [command_buffer commit];
     impl_->rendered_stream.assign(remote_id);

apps/desktop/src/platform/single_instance.h

@@ -0,0 +1,53 @@
+/*
+ * @Author: DI JUNKUN
+ * @Date: 2026-09-26
+ * Copyright (c) 2026 by DI JUNKUN, All Rights Reserved.
+ */
+
+#ifndef _SINGLE_INSTANCE_H_
+#define _SINGLE_INSTANCE_H_
+
+#include <cstdint>
+#include <string>
+
+namespace crossdesk::platform {
+
+enum class InstanceRole { kLauncher, kClient, kServiceCli };
+enum class InstanceResult { kAcquired, kAlreadyRunning, kError };
+
+// Per-user ownership, independent of the install/portable directory. The OS
+// releases ownership on process exit, including crashes; no PID files to age out.
+class SingleInstanceGuard {
+ public:
+  explicit SingleInstanceGuard(std::string application = "CrossDesk");
+  ~SingleInstanceGuard();
+  SingleInstanceGuard(const SingleInstanceGuard&) = delete;
+  SingleInstanceGuard& operator=(const SingleInstanceGuard&) = delete;
+
+  InstanceResult TryAcquire(InstanceRole role, std::string& error);
+  void Release();
+
+ private:
+  std::string application_;
+  std::intptr_t handle_ = -1;
+};
+
+inline const char* InstanceRoleName(InstanceRole role) {
+  switch (role) {
+    case InstanceRole::kLauncher: return "launcher";
+    case InstanceRole::kClient: return "client";
+    case InstanceRole::kServiceCli: return "service-cli";
+  }
+  return "client";
+}
+
+inline bool ValidInstanceApplication(const std::string& application) {
+  return !application.empty() && application.size() <= 100 &&
+         application.find_first_not_of(
+             "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_") ==
+             std::string::npos;
+}
+
+}  // namespace crossdesk::platform
+
+#endif

apps/desktop/src/platform/video_renderer.h

@@ -9,6 +9,7 @@
 #include <vector>
 
 #include "minirtc.h"
+#include "rendering/video_latency.h"
 
 namespace crossdesk {
 
@@ -54,14 +55,17 @@ public:
 
   virtual SubmitResult SubmitNv12(std::string_view remote_id,
                                   const uint8_t* data, size_t size, int width,
-                                  int height) = 0;
+                                  int height,
+                                  VideoLatencyFrame timing = {}) = 0;
   virtual SubmitResult SubmitCachedNv12(std::string_view remote_id,
                                         const uint8_t* data, size_t size,
-                                        int width, int height) = 0;
+                                        int width, int height,
+                                        VideoLatencyFrame timing = {}) = 0;
   // Retains a platform-native decoded frame when the backend supports its
   // storage and handle types. Unsupported backends keep the default fallback.
   virtual SubmitResult SubmitNativeFrame(std::string_view,
-                                         const MiniRtcNativeVideoFrame&) {
+                                         const MiniRtcNativeVideoFrame&,
+                                         VideoLatencyFrame = {}) {
     return SubmitResult::failed;
   }
 

apps/desktop/src/platform/windows/screen_capturer/screen_capturer_dxgi.cpp

@@ -547,7 +547,7 @@ void ScreenCapturerDxgi::CaptureLoop() {
       if (last_logged_cursor_embedding_ < 0 ||
           (software_cursor_output_ &&
            last_logged_cursor_embedding_ != static_cast<int>(cursor_embedded))) {
-        LOG_INFO("DXGI cursor: monitor={} usbmmidd={} mouse_update={} "
+        LOG_DEBUG("DXGI cursor: monitor={} usbmmidd={} mouse_update={} "
                  "separate_pointer_visible={} pointer_shape_bytes={} "
                  "compose_cursor={} embedded={}",
                  frame_monitor, software_cursor_output_,

apps/desktop/src/platform/windows/screen_capturer/screen_capturer_win.cpp

@@ -1638,7 +1638,7 @@ void ScreenCapturerWin::SecureDesktopCaptureLoop() {
     const ULONGLONG elapsed = GetTickCount64() - stats_started;
     if (elapsed == 0 || (!force && elapsed < 5000)) return;
     if (shared_frames || fallback_frames || shared_waits || shared_restarts) {
-      LOG_INFO(
+      LOG_DEBUG(
           "Secure capture delivery: shared_fps={:.1f}, fallback_fps={:.1f}, "
           "pending_waits={}, shared_restarts={}, status_max_ms={}",
           shared_frames * 1000.0 / elapsed, fallback_frames * 1000.0 / elapsed,

apps/desktop/src/platform/windows/screen_capturer/wgc_plugin_entry.cpp

@@ -12,7 +12,7 @@ void InitializePluginLogger() {
   static std::once_flag once;
   std::call_once(once, []() {
     crossdesk::PathManager path_manager("CrossDesk");
-    crossdesk::InitLogger(path_manager.GetLogPath().string());
+    crossdesk::InitLogger(path_manager.GetLogPath().string(), "crossdesk-wgc");
   });
 }
 

apps/desktop/src/platform/windows/single_instance.cpp

@@ -0,0 +1,71 @@
+#include "platform/single_instance.h"
+
+#include <windows.h>
+#include <sddl.h>
+
+#include <utility>
+#include <vector>
+
+namespace crossdesk::platform {
+
+SingleInstanceGuard::SingleInstanceGuard(std::string application)
+    : application_(std::move(application)) {}
+
+SingleInstanceGuard::~SingleInstanceGuard() { Release(); }
+
+InstanceResult SingleInstanceGuard::TryAcquire(InstanceRole role,
+                                               std::string& error) {
+  error.clear();
+  if (handle_ != -1) return InstanceResult::kAcquired;
+  if (!ValidInstanceApplication(application_)) {
+    error = "Invalid single-instance application name";
+    return InstanceResult::kError;
+  }
+  HANDLE token = nullptr;
+  if (!OpenProcessToken(GetCurrentProcess(), TOKEN_QUERY, &token)) {
+    error = "Cannot read current user token: " + std::to_string(GetLastError());
+    return InstanceResult::kError;
+  }
+  DWORD size = 0;
+  GetTokenInformation(token, TokenUser, nullptr, 0, &size);
+  std::vector<unsigned char> buffer(size);
+  if (!GetTokenInformation(token, TokenUser, buffer.data(), size, &size)) {
+    const DWORD code = GetLastError();
+    CloseHandle(token);
+    error = "Cannot read current user SID: " + std::to_string(code);
+    return InstanceResult::kError;
+  }
+  CloseHandle(token);
+  wchar_t* sid = nullptr;
+  if (!ConvertSidToStringSidW(reinterpret_cast<TOKEN_USER*>(buffer.data())->User.Sid,
+                             &sid)) {
+    error = "Cannot format current user SID: " + std::to_string(GetLastError());
+    return InstanceResult::kError;
+  }
+  const std::string role_name = InstanceRoleName(role);
+  const std::wstring name = L"Global\\" +
+      std::wstring(application_.begin(), application_.end()) + L"." + sid + L"." +
+      std::wstring(role_name.begin(), role_name.end());
+  LocalFree(sid);
+  // Object lifetime is the lease. No thread-owned mutex to transfer to a daemon.
+  HANDLE mutex = CreateMutexW(nullptr, FALSE, name.c_str());
+  const DWORD code = GetLastError();
+  if (!mutex) {
+    error = "Cannot create single-instance mutex: " + std::to_string(code);
+    return InstanceResult::kError;
+  }
+  if (code == ERROR_ALREADY_EXISTS) {
+    CloseHandle(mutex);
+    return InstanceResult::kAlreadyRunning;
+  }
+  handle_ = reinterpret_cast<std::intptr_t>(mutex);
+  return InstanceResult::kAcquired;
+}
+
+void SingleInstanceGuard::Release() {
+  if (handle_ == -1) return;
+  CloseHandle(reinterpret_cast<HANDLE>(handle_));
+  handle_ = -1;
+}
+
+}  // namespace crossdesk::platform

apps/desktop/xmake/options.lua

@@ -38,7 +38,9 @@ function setup_options_and_dependencies()
     add_defines("USE_WAYLAND=" .. (is_config("USE_WAYLAND", true) and "1" or "0"))
     add_defines("USE_DRM=" .. (is_config("USE_DRM", true) and "1" or "0"))
     if is_mode("debug") then
-        add_defines("CROSSDESK_DEBUG")
+        add_defines("CROSSDESK_DEBUG", "SPDLOG_ACTIVE_LEVEL=SPDLOG_LEVEL_DEBUG")
+    else
+        add_defines("SPDLOG_ACTIVE_LEVEL=SPDLOG_LEVEL_INFO")
     end
 
     add_requireconfs("**.python", {version = "3.12", override = true, configs = {pgo = false}})

apps/desktop/xmake/targets.lua

@@ -135,6 +135,16 @@ function setup_targets()
             "apps/desktop/src/gui/runtime")
         add_files("apps/desktop/tests/cursor_position_test.cpp")
 
+    target("single_instance")
+        set_kind("object")
+        add_includedirs("apps/desktop/src", {public = true})
+        if is_os("windows") then
+            add_files("apps/desktop/src/platform/windows/single_instance.cpp")
+            add_syslinks("Advapi32")
+        else
+            add_files("apps/desktop/src/platform/common/posix_single_instance.cpp")
+        end
+
     target("repository_structure_test")
         set_kind("binary")
         set_default(false)
@@ -540,7 +550,7 @@ function setup_targets()
 
     target("crossdesk")
         set_kind("binary")
-        add_deps("rd_log", "desktop_common", "gui")
+        add_deps("rd_log", "desktop_common", "gui", "single_instance")
         add_files("apps/desktop/src/app/*.cpp")
         add_includedirs("apps/desktop/src", "apps/desktop/src/app", {public = true})
         if is_os("windows") then