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#pragma once
#include <chrono>
#include "Manager.h"
namespace crepe {
class Engine;
typedef std::chrono::duration<float> duration_t;
typedef std::chrono::duration<unsigned long long, std::micro> elapsed_time_t;
/**
* \brief Manages timing and frame rate for the game loop.
*
* The LoopTimerManager class is responsible for calculating and managing timing functions
* such as delta time, frames per second (FPS), fixed time steps, and time scaling. It ensures
* consistent frame updates and supports game loop operations, such as handling fixed updates
* for physics and other time-sensitive operations.
*/
class LoopTimerManager : public Manager {
public:
/**
* \param mediator A reference to a Mediator object used for transfering managers.
*/
LoopTimerManager(Mediator & mediator);
/**
* \brief Get the current delta time for the current frame.
*
* This value represents the estimated frame duration of the current frame.
* This value can be used in the frame_update to convert pixel based values to time based values.
*
* \return Delta time in seconds since the last frame.
*/
duration_t get_delta_time() const;
/**
* \brief Get the current elapsed time (total time passed )
*
* \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.
*/
elapsed_time_t get_elapsed_time() const;
/**
* \brief Set the target frames per second (FPS).
*
* \param fps The desired frames rendered per second.
*/
void set_target_framerate(unsigned fps);
/**
* \brief Get the current frames per second (FPS).
*
* \return Current FPS.
*/
unsigned int get_fps() const;
/**
* \brief Get the current time scale.
*
* \return The current time scale, where (0 = pause, < 1 = slow down, 1 = normal speed, > 1 = speed up).
* up the game.
*/
float get_time_scale() const;
/**
* \brief Set the time scale.
*
* time_scale is a value that changes the delta time that can be retrieved using get_delta_time function.
*
* \param time_scale The desired time scale (0 = pause, < 1 = slow down, 1 = normal speed, > 1 = speed up).
*/
void set_time_scale(double time_scale);
/**
* \brief Get the fixed delta time in seconds without scaling by the time scale.
*
* This value is used in the LoopManager to determine how many times
* the fixed_update should be called within a given interval.
*
* \return The unscaled fixed delta time in seconds.
*/
duration_t get_fixed_delta_time() const;
/**
* \brief Set the fixed_delta_time in seconds.
*
* \param seconds fixed_delta_time in seconds.
*
* The fixed_delta_time value is used to determine how many times per second the fixed_update and process_input functions are called.
*
*/
void set_fixed_delta_time(float seconds);
/**
* \brief Retrieves the scaled fixed delta time in seconds.
*
* The scaled fixed delta time is the timing value used within the `fixed_update` function.
* It is adjusted by the time_scale to account for any changes in the simulation's
* speed.
*
* \return The fixed delta time, scaled by the current time scale, in seconds.
*/
duration_t get_scaled_fixed_delta_time() const;
private:
//! Friend relation to use start,enforce_frame_rate,get_lag,update,advance_fixed_update.
friend class Engine;
/**
* \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 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.
*/
duration_t get_lag() const;
/**
* \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 Progress the elapsed fixed time by the fixed delta time interval.
*
* This method advances the game's fixed update loop by adding the fixed_delta_time
* to elapsed_fixed_time, ensuring the fixed update catches up with the elapsed time.
*/
void advance_fixed_elapsed_time();
private:
//! Target frames per second.
unsigned int target_fps = 60;
//! Actual frames per second.
unsigned int actual_fps = 0;
//! Time scale for speeding up or slowing down the game (0 = pause, < 1 = slow down, 1 = normal speed, > 1 = speed up).
float time_scale = 1;
//! Maximum delta time in seconds to avoid large jumps.
duration_t maximum_delta_time{0.25};
//! Delta time for the current frame in seconds.
duration_t delta_time{0.0};
//! Target time per frame in seconds
duration_t frame_target_time{1.0 / target_fps};
//! Fixed delta time for fixed updates in seconds.
duration_t fixed_delta_time{1.0 / 50.0};
//! Total elapsed game time in microseconds.
elapsed_time_t elapsed_time{0};
//! Total elapsed time for fixed updates in microseconds.
elapsed_time_t elapsed_fixed_time{0};
typedef std::chrono::steady_clock::time_point time_point_t;
//! Time of the last frame.
time_point_t last_frame_time;
};
} // namespace crepe
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