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#pragma once
#include <chrono>
namespace crepe {
class LoopTimer {
public:
/**
* \brief Get the singleton instance of LoopTimer.
*
* \return A reference to the LoopTimer instance.
*/
static LoopTimer & get_instance();
/**
* \brief Get the current delta time for the current frame.
*
* \return Delta time in seconds since the last frame.
*/
double get_delta_time() const;
/**
* \brief Get the current game time.
*
* \note The current game time may vary from real-world elapsed time.
* It is the cumulative sum of each frame's delta time.
*
* \return Elapsed game time in seconds.
*/
double get_current_time() const;
/**
* \brief Set the target frames per second (FPS).
*
* \param fps The desired frames rendered per second.
*/
void set_fps(int fps);
/**
* \brief Get the current frames per second (FPS).
*
* \return Current FPS.
*/
int get_fps() const;
/**
* \brief Get the current game scale.
*
* \return The current game scale, where 0 = paused, 1 = normal speed, and values > 1 speed up the game.
*/
double get_game_scale() const;
/**
* \brief Set the game scale.
*
* \param game_scale The desired game scale (0 = pause, 1 = normal speed, > 1 = speed up).
*/
void set_game_scale(double game_scale);
private:
friend class LoopManager;
/**
* \brief Start the loop timer.
*
* Initializes the timer to begin tracking frame times.
*/
void start();
/**
* \brief Enforce the frame rate limit.
*
* Ensures that the game loop does not exceed the target FPS by delaying
* frame updates as necessary.
*/
void enforce_frame_rate();
/**
* \brief Get the fixed delta time for consistent updates.
*
* Fixed delta time is used for operations that require uniform time steps,
* such as physics calculations.
*
* \return Fixed delta time in seconds.
*/
double get_fixed_delta_time() const;
/**
* \brief Get the accumulated lag in the game loop.
*
* Lag represents the difference between the target frame time and the
* actual frame time, useful for managing fixed update intervals.
*
* \return Accumulated lag in seconds.
*/
double get_lag() const;
/**
* \brief Construct a new LoopTimer object.
*
* Private constructor for singleton pattern to restrict instantiation
* outside the class.
*/
LoopTimer();
/**
* \brief Update the timer to the current frame.
*
* Calculates and updates the delta time for the current frame and adds it to
* the cumulative game time.
*/
void update();
/**
* \brief Advance the game loop by a fixed update interval.
*
* This method progresses the game state by a consistent, fixed time step,
* allowing for stable updates independent of frame rate fluctuations.
*/
void advance_fixed_update();
private:
//! Current frames per second
int fps = 50;
//! Current game scale
double game_scale = 1;
//! Maximum delta time in seconds to avoid large jumps
std::chrono::duration<double> maximum_delta_time{0.25};
//! Delta time for the current frame in seconds
std::chrono::duration<double> delta_time{0.0};
//! Target time per frame in seconds
std::chrono::duration<double> frame_target_time
= std::chrono::seconds(1) / fps;
//! Fixed delta time for fixed updates in seconds
std::chrono::duration<double> fixed_delta_time
= std::chrono::seconds(1) / 50;
//! Total elapsed game time in seconds
std::chrono::duration<double> elapsed_time{0.0};
//! Total elapsed time for fixed updates in seconds
std::chrono::duration<double> elapsed_fixed_time{0.0};
//! Time of the last frame
std::chrono::steady_clock::time_point last_frame_time;
};
} // namespace crepe
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