From 3d0de3f951ec2da7a2d41c6958d0d3583a7832a0 Mon Sep 17 00:00:00 2001
From: HampusM <hampus@hampusmat.com>
Date: Tue, 24 Oct 2023 21:44:56 +0200
Subject: feat(engine): add delta time
---
engine/src/lib.rs | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
(limited to 'engine/src')
diff --git a/engine/src/lib.rs b/engine/src/lib.rs
index ce953f8..bec1e30 100644
--- a/engine/src/lib.rs
+++ b/engine/src/lib.rs
@@ -1,6 +1,7 @@
#![deny(clippy::all, clippy::pedantic)]
use std::collections::BTreeMap;
+use std::time::{Duration, Instant};
use glfw::{Window, WindowBuilder};
@@ -29,6 +30,7 @@ pub struct Engine
objects: BTreeMap<ObjectId, Object>,
window: Window,
camera: Camera,
+ delta_time: Duration,
}
impl Engine
@@ -63,6 +65,7 @@ impl Engine
window,
objects: BTreeMap::new(),
camera: Camera::new(),
+ delta_time: Duration::ZERO,
})
}
@@ -95,7 +98,11 @@ impl Engine
/// Will return `Err` if updating the window fails.
pub fn start(&mut self, mut func: impl FnMut(&mut Self)) -> Result<(), Error>
{
+ let mut prev_frame_start: Option<Instant> = None;
+
while !self.window.should_close() {
+ self.update_delta_time(&mut prev_frame_start);
+
func(self);
let window_size = self.window.size().map_err(Error::GetWindowSizeFailed)?;
@@ -118,6 +125,25 @@ impl Engine
{
&mut self.camera
}
+
+ /// Returns the current delta time. Will be 0 if not called from the function
+ /// passed to [`start`].
+ #[must_use]
+ pub fn delta_time(&self) -> &Duration
+ {
+ &self.delta_time
+ }
+
+ fn update_delta_time(&mut self, prev_frame_start: &mut Option<Instant>)
+ {
+ let frame_start_time = Instant::now();
+
+ if let Some(last_frame_start) = prev_frame_start {
+ self.delta_time = frame_start_time.duration_since(*last_frame_start);
+ }
+
+ *prev_frame_start = Some(frame_start_time);
+ }
}
/// Engine Error
--
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