include/canvas/elapsedtime.hxx

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  19
  20 #ifndef INCLUDED_CANVAS_ELAPSEDTIME_HXX
  21 #define INCLUDED_CANVAS_ELAPSEDTIME_HXX
  22
  23 #include <canvas/canvastoolsdllapi.h>
  24 #include <memory>
  25
  26 namespace canvas::tools
  27 {
  28         /** Calculate elapsed time.
  29
  30             This class provides several time-measurement and
  31             -management functions. In its simplest use-case, it
  32             measures the time from its creation.
  33          */
  34         class CANVASTOOLS_DLLPUBLIC ElapsedTime
  35         {
  36         public:
  37             /** Create a new ElapsedTime object
  38
  39                 The moment of construction starts the time
  40                 measurement. That means, a subsequent getElapsedTime()
  41                 call will return the time difference between object
  42                 creation and getElapsedTime() call.
  43              */
  44             ElapsedTime();
  45
  46             /** Creates a new ElapsedTime object based on another
  47                 timer.
  48
  49                 The moment of construction starts the time
  50                 measurement. That means, a subsequent getElapsedTime()
  51                 call will return the time difference between object
  52                 creation and getElapsedTime() call. All time values
  53                 are not taken from the system's time base, but from
  54                 the provided timer.
  55              */
  56             ElapsedTime( std::shared_ptr<ElapsedTime> const & pTimeBase );
  57
  58             /** Reset the time
  59
  60                 The instance of the reset() call starts the time
  61                 measurement from scratch. That means, a subsequent
  62                 getElapsedTime() call will return the time difference
  63                 between reset() and getElapsedTime() call.
  64              */
  65             void reset();
  66
  67             /** Query the elapsed time
  68
  69                 This method returns the elapsed time in seconds
  70                 between either the construction of this object, or the
  71                 last reset() call, if any (but see the time modulation
  72                 methods below, for means to modify the otherwise
  73                 continuous flow of time).
  74
  75                 @return the elapsed time in seconds.
  76              */
  77             double getElapsedTime() const;
  78
  79             /** Pauses the running timer.
  80
  81                 This method stops the time, as returned by this
  82                 object, until continueTimer() is called. During this
  83                 period, getElapsedTime() will always return the same
  84                 time value (i.e. the instant when pauseTimer() was
  85                 called).
  86              */
  87             void pauseTimer();
  88
  89             /** Continues the paused timer.
  90
  91                 This method re-enables the time flow, that is, time
  92                 starts running again for clients calling
  93                 getElapsedTime(). The (subtle) difference to the
  94                 holdTimer/releaseTimer() methods below is, that there
  95                 is no perceived time 'jump' between the pauseTimer()
  96                 call and the continueTimer() call, i.e. the time
  97                 starts over with the same value it has stopped on
  98                 pauseTimer().
  99              */
 100             void continueTimer();
 101
 102             /** Adjusts the timer, hold and pause times.
 103
 104                 This method modifies the time as returned by this
 105                 object by the specified amount. This affects the time
 106                 as returned by getElapsedTime(), regardless of the
 107                 mode (e.g. paused, or on hold).
 108
 109                 @param fOffset
 110                 This value will be added to the current time, i.e. the
 111                 next call to getElapsedTime() (when performed
 112                 immediately) will be adjusted by fOffset.
 113             */
 114             void adjustTimer( double fOffset );
 115
 116             /** Holds the current time.
 117
 118                 This call makes the timer hold the current time
 119                 (e.g. getElapsedTime() will return the time when
 120                 holdTimer() was called), while the underlying time is
 121                 running on. When releaseTimer() is called, the time
 122                 will 'jump' to the then-current, underlying time. This
 123                 is equivalent to pressing the "interim time" button on
 124                 a stop watch, which shows this stopped time, while the
 125                 clock keeps running internally.
 126             */
 127             void holdTimer();
 128
 129             /** Releases a held timer.
 130
 131                 After this call, the timer again returns the running
 132                 time on getElapsedTime().
 133              */
 134             void releaseTimer();
 135
 136         private:
 137             static double getSystemTime();
 138             double getCurrentTime() const;
 139             double getElapsedTimeImpl() const; // does not set m_fLastQueriedTime
 140
 141             const std::shared_ptr<ElapsedTime>  m_pTimeBase;
 142
 143             /// To validate adjustTimer() calls with bLimitToLastQueriedTime=true
 144             mutable double                          m_fLastQueriedTime;
 145
 146             /// Start time, from which the difference to the time base is returned
 147             double                                  m_fStartTime;
 148
 149             /// Instant, when last pause or hold started, relative to m_fStartTime
 150             double                                  m_fFrozenTime;
 151
 152             /// True, when in pause mode
 153             bool                                    m_bInPauseMode;
 154
 155             /// True, when in hold mode
 156             bool                                    m_bInHoldMode;
 157         };
 158
 159 }
 160
 161 #endif /* INCLUDED_CANVAS_ELAPSEDTIME_HXX */
 162
 163 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */