[feat] add video latency to network statistics

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 +1,104 @@
+/*
+ * @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 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 {
+  if (stats) stats->Record(*this, now);
+}
+}  // namespace crossdesk
+
+#endif