frametimer.h

Single-header frametimer utility

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Very basic utility to lock the execution rate of a function to a specific frameratei using polling. It is dependency free (even from the standard library) which makes it very portable. It does not perform any memory allocation.

Usage

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Include the header file in every file you want to use it.

#include "frametimer.h"

In ONE file, define FRAMETIMER_IMPL before including the header file.

#define FRAMETIMER_IMPL
#include "frametimer.h"

Define a function and allocate a frametimer

void print_delta(unsigned int dt) {
  printf("Delta time is %d\n", dt);
}

frametimer_t ft_print_delta = {
  .fps  = 1,
  .func = print_delta
};

Then in your update loop call ft_update and give it the current time using the method of your choice. This is platform dependant, the only constraint is that time must be expressed in milliseconds.

while (true) {
  unsigned int time = get_time()
  int ran = ft_update(&ft_print_delta, time);
}

The function print_delta will be executed once per second. ran will be 1 if print_delta executed, and 0 if it did not. This can be useful to skip some other actions based on whether or not its dependencies executed.

Documentation

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typedef void (*ft_func_t)(unsigned int dt);

The function you want to bind to a frametimer_t should be of this shape. It takes an unsigned int as an argument which will be the delta between this execution and the previous one, and returns void.

typedef struct {
  ft_func_t func;
  unsigned int fps;
  unsigned int last_run;
  unsigned int run_count;  
} frametimer_t;

A frametimer_t is a simple struct that stores the pointer to the function to be executed, the framerate at which it should be executed, the timestamp of the last run, and the number of time the function has been called since the start of the program.

int ft_update(frametimer_t* ft, unsigned int time);

Calls the function bound to ft if the delta between time and its last execution matches the framerate specified.