Print frame processing latency to debug log

src/stat_trackers.h

@@ -0,0 +1,41 @@
+#pragma once
+
+#include <chrono>
+#include <functional>
+#include <limits>
+
+#include <boost/format.hpp>
+
+namespace stat_trackers {
+
+  boost::format
+  one_digit_after_decimal();
+
+  template <typename T>
+  class min_max_avg_tracker {
+  public:
+    using callback_function = std::function<void(T stat_min, T stat_max, double stat_avg)>;
+
+    void
+    collect_and_callback_on_interval(T stat, const callback_function &callback, std::chrono::seconds interval_in_seconds) {
+      if (std::chrono::steady_clock::now() > data.last_callback_time + interval_in_seconds) {
+        callback(data.stat_min, data.stat_max, data.stat_total / data.calls);
+        data = {};
+      }
+      data.stat_min = std::min(data.stat_min, stat);
+      data.stat_max = std::max(data.stat_max, stat);
+      data.stat_total += stat;
+      data.calls += 1;
+    }
+
+  private:
+    struct {
+      std::chrono::steady_clock::steady_clock::time_point last_callback_time = std::chrono::steady_clock::now();
+      T stat_min = std::numeric_limits<T>::max();
+      T stat_max = 0;
+      double stat_total = 0;
+      uint32_t calls = 0;
+    } data;
+  };
+
+}  // namespace stat_trackers