2021-32-bit-holiday-jam/src/timestep.rs

50 lines
975 B
Rust

use std::time::Instant;
pub struct TimeStep {
last_frame_time: Instant,
// Milliseconds
accum: u128,
fps_num: u16,
fps_den: u16,
}
impl TimeStep {
pub fn new (fps_num: u16, fps_den: u16) -> Self {
Self {
last_frame_time: Instant::now (),
accum: 0,
fps_num,
fps_den,
}
}
// Automatically gets monotonic system time from Instant
// If you need something fancy just rewrite this.
// Returns: How many logics steps to run. Typically 0 or 1.
pub fn step (&mut self) -> u16 {
let frame_time = Instant::now ();
let fps_num_128: u128 = self.fps_num.into ();
let fps_den_128: u128 = self.fps_den.into ();
self.accum += (frame_time - self.last_frame_time).as_millis () * fps_num_128;
let mut result = 0;
const MAX_FRAMES: u16 = 4;
for _ in 0..MAX_FRAMES {
if self.accum > fps_den_128 {
result += 1;
self.accum -= fps_den_128;
}
else {
break;
}
}
self.last_frame_time = frame_time;
result
}
}