1 files changed, 42 insertions, 2 deletions

diff --git a/UI.h b/UI.h
index fa89c52..bbc5a7d 100644
--- a/UI.h
+++ b/UI.h
@@ -26,6 +26,46 @@ private:
   std::chrono::time_point<clock_type> m_checkpoint_timestamp{};
 };
 
+template<typename T>
+class AgeOutValue
+{
+public:
+  AgeOutValue(std::chrono::milliseconds timeout):
+    m_timeout(timeout),
+    m_checkpoint_timestamp(clock_type::now()),
+    m_value{}
+  {
+  }
+
+  bool is_current()
+  {
+    return clock_type::now() - m_checkpoint_timestamp < m_timeout;
+  }
+
+  // returns value, or 0 if aged-out
+  T value()
+  {
+    T result{};
+
+    if (is_current()) {
+      result = m_value;
+    }
+
+    return result;
+  }
+
+  void update(const T& value)
+  {
+    m_value = value;
+    m_checkpoint_timestamp = clock_type::now();
+  }
+
+private:
+  const std::chrono::milliseconds m_timeout;
+  std::chrono::time_point<clock_type> m_checkpoint_timestamp{};
+  T m_value;
+};
+
 class UI
 {
 public:
@@ -66,8 +106,8 @@ private:
   uint64_t m_midi_timestamp;
   std::deque<std::pair<int,int>> m_midi_monitor;
 
-  int m_note_bpm;
-  int m_clock_bpm;
+  AgeOutValue<int> m_note_bpm;
+  AgeOutValue<int> m_clock_bpm;
 
   Touchpad m_touchpad;
   Temperature m_temperature;