1 files changed, 177 insertions, 0 deletions
diff --git a/src/crepe/manager/LoopTimerManager.h b/src/crepe/manager/LoopTimerManager.h
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+++ b/src/crepe/manager/LoopTimerManager.h
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+#pragma once
+
+#include <chrono>
+
+#include "Manager.h"
+
+namespace crepe {
+
+class Engine;
+
+typedef std::chrono::duration<double> 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 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 target_fps = 60;
+	//! Actual frames per second.
+	unsigned 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