[fix] add capture delivery diagnostics

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

@@ -33,6 +33,8 @@ namespace {
 
 using Json = nlohmann::json;
 
+thread_local bool current_frame_from_secure_desktop = false;
+
 constexpr DWORD kSecureDesktopStatusIntervalMs = 250;
 constexpr DWORD kSecureDesktopStatusPipeTimeoutMs = 500;
 constexpr DWORD kSecureDesktopHelperPipeTimeoutMs = 120;
@@ -460,6 +462,10 @@ int ScreenCapturerWin::Destroy() {
   return 0;
 }
 
+bool ScreenCapturerWin::CurrentFrameIsFromSecureDesktop() {
+  return current_frame_from_secure_desktop;
+}
+
 void ScreenCapturerWin::EmitCapturedFrame(
     unsigned char* data, int size, int width, int height,
     const char* stream_id, const MiniRtcNativeVideoFrame* native_frame,
@@ -473,6 +479,14 @@ void ScreenCapturerWin::EmitCapturedFrame(
     return;
   }
 
+  // Normal and helper callbacks can originate on different threads during
+  // desktop transitions. Keep diagnostics tied to this callback's source.
+  struct RestoreFrameSource {
+    bool previous;
+    ~RestoreFrameSource() { current_frame_from_secure_desktop = previous; }
+  } restore_source{
+      std::exchange(current_frame_from_secure_desktop, from_secure_desktop)};
+
   if (native_frame) {
     if (!native_output_logged_.exchange(true, std::memory_order_relaxed)) {
       LOG_INFO("Windows capturer native frame output enabled (type={})",

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

@@ -48,6 +48,9 @@ class ScreenCapturerWin : public ScreenCapturer {
   void SetPrivacyController(PrivacyController* privacy) override { privacy_ = privacy; }
   // Set before Init(), while capture is stopped.
   void SetCaptureMethod(ScreenCaptureMethod method) { capture_method_ = method; }
+  // Query synchronously inside the frame callback, on the delivering thread.
+  // This describes the actual frame, independently of service status polling.
+  static bool CurrentFrameIsFromSecureDesktop();
 
  private:
   std::unique_ptr<ScreenCapturer> impl_;