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#ifndef TIMER_SYNC_H
#define TIMER_SYNC_H
#include "core/engine.h"
struct MainFrameTime {
float idle_step; // time to advance idles for (argument to process())
int physics_steps; // number of times to iterate the physics engine
void clamp_idle(float min_idle_step, float max_idle_step);
};
class MainTimerSync {
// wall clock time measured on the main thread
uint64_t last_cpu_ticks_usec;
uint64_t current_cpu_ticks_usec;
// logical game time since last physics timestep
float time_accum;
// current difference between wall clock time and reported sum of idle_steps
float time_deficit;
// number of frames back for keeping accumulated physics steps roughly constant.
// value of 12 chosen because that is what is required to make 144 Hz monitors
// behave well with 60 Hz physics updates. The only worse commonly available refresh
// would be 85, requiring CONTROL_STEPS = 17.
static const int CONTROL_STEPS = 12;
// sum of physics steps done over the last (i+1) frames
int accumulated_physics_steps[CONTROL_STEPS];
// typical value for accumulated_physics_steps[i] is either this or this plus one
int typical_physics_steps[CONTROL_STEPS];
int fixed_fps;
protected:
// returns the fraction of p_frame_slice required for the timer to overshoot
// before advance_core considers changing the physics_steps return from
// the typical values as defined by typical_physics_steps
float get_physics_jitter_fix();
// gets our best bet for the average number of physics steps per render frame
// return value: number of frames back this data is consistent
int get_average_physics_steps(float &p_min, float &p_max);
// advance physics clock by p_idle_step, return appropriate number of steps to simulate
MainFrameTime advance_core(float p_frame_slice, int p_iterations_per_second, float p_idle_step);
// calls advance_core, keeps track of deficit it adds to animaption_step, make sure the deficit sum stays close to zero
MainFrameTime advance_checked(float p_frame_slice, int p_iterations_per_second, float p_idle_step);
// determine wall clock step since last iteration
float get_cpu_idle_step();
public:
MainTimerSync();
// start the clock
void init(uint64_t p_cpu_ticks_usec);
// set measured wall clock time
void set_cpu_ticks_usec(uint64_t p_cpu_ticks_usec);
//set fixed fps
void set_fixed_fps(int p_fixed_fps);
// advance one frame, return timesteps to take
MainFrameTime advance(float p_frame_slice, int p_iterations_per_second);
};
#endif // TIMER_SYNC_H
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