cabana: stable FPS (#26120)

* stable FPS

* fix
old-commit-hash: 686506f400

tools/cabana/canmessages.cc

@@ -87,7 +87,7 @@ void CANMessages::process(QHash<QString, std::deque<CanData>> *messages) {
 }
 
 bool CANMessages::eventFilter(const Event *event) {
-  static double prev_update_sec = 0;
+  static double prev_update_ts = 0;
   // drop packets when the GUI thread is calling seekTo. to make sure the current_sec is accurate.
   if (!seeking && event->which == cereal::Event::Which::CAN) {
     if (!received_msgs) {
@@ -121,8 +121,9 @@ bool CANMessages::eventFilter(const Event *event) {
       }
     }
 
-    if (current_sec < prev_update_sec || (current_sec - prev_update_sec) > 1.0 / settings.fps) {
-      prev_update_sec = current_sec;
+    double ts = millis_since_boot();
+    if ((ts - prev_update_ts) > (1000.0 / settings.fps)) {
+      prev_update_ts = ts;
       // use pointer to avoid data copy in queued connection.
       emit received(received_msgs.release());
     }