Add last_viewed_time and accessor functions

src/zm_monitor.h

@@ -195,7 +195,11 @@ protected:
       time_t last_read_time;
       uint64_t extrapad4;
     };
-    uint8_t control_state[256];  /* +104   */
+    union {                     /* +104  */
+      time_t last_viewed_time;
+      uint64_t extrapad5;
+    };
+    uint8_t control_state[256];  /* +112   */
 
     char alarm_cause[256];
     char video_fifo_path[64];
@@ -518,6 +522,25 @@ public:
       return false;
     return (enabled && shared_data->active);
   }
+  int64_t getLastViewed() {
+    if (shared_data && shared_data->valid)
+      return shared_data->last_viewed_time;
+    return 0;
+  }
+  void setLastViewed(SystemTimePoint new_time) {
+    if (shared_data && shared_data->valid)
+      shared_data->last_viewed_time = 
+        static_cast<int64>(std::chrono::duration_cast<Seconds>(new_time.time_since_epoch()).count());
+  }
+  bool hasViewers() {
+    if (shared_data && shared_data->valid) {
+      TimePoint now = std::chrono::steady_clock::now();;
+      return (
+          (shared_data->last_viewed_time - static_cast<int64>(std::chrono::duration_cast<Seconds>(now.time_since_epoch()).count())
+          ) > 1 ? false : true);
+    }
+    return false;
+  }
   inline bool Exif() const { return embed_exif; }
   inline bool RTSPServer() const { return rtsp_server; }
   inline bool RecordAudio() const { return record_audio; }