change displaying of fps to time (ms)

samples/opengl/winapp.hpp

@@ -22,6 +22,54 @@
 
 #define SAFE_RELEASE(p) if (p) { p->Release(); p = NULL; }
 
+class Timer
+{
+public:
+    enum UNITS
+    {
+        USEC = 0,
+        MSEC,
+        SEC
+    };
+
+    Timer() : m_t0(0), m_diff(0)
+    {
+        m_tick_frequency = (float)cv::getTickFrequency();
+
+        m_unit_mul[USEC] = 1000000;
+        m_unit_mul[MSEC] = 1000;
+        m_unit_mul[SEC]  = 1;
+    }
+
+    void clear()
+    {
+        m_t0 = m_diff = 0;
+    }
+
+    void start()
+    {
+        m_t0 = cv::getTickCount();
+    }
+
+    void stop()
+    {
+        m_diff = cv::getTickCount() - m_t0;
+    }
+
+    float time(UNITS u = UNITS::MSEC)
+    {
+        float sec = m_diff / m_tick_frequency;
+
+        return sec * m_unit_mul[u];
+    }
+
+public:
+    float m_tick_frequency;
+    int64 m_t0;
+    int64 m_diff;
+    int   m_unit_mul[3];
+};
+
 class WinApp
 {
 public:
@@ -218,4 +266,5 @@ protected:
     int          m_width;
     int          m_height;
     std::string  m_window_name;
+    Timer        m_timer;
 };