renderbug: first implementation of surface-based rendering

src/time.rs

@@ -0,0 +1,30 @@
+use std::time::{Instant, Duration};
+
+pub struct Periodically {
+    last_run: Instant,
+    duration: Duration
+}
+
+impl Periodically {
+    pub fn new(duration: Duration) -> Self {
+        Self {
+            last_run: Instant::now(),
+            duration: duration
+        }
+    }
+
+    pub fn new_every_n_seconds(seconds: u64) -> Self {
+        Self::new(Duration::new(seconds, 0))
+    }
+
+    pub fn new_every_n_ms(milliseconds: u32) -> Self {
+        Self::new(Duration::new(0, milliseconds*1000))
+    }
+
+    pub fn run<F>(&mut self, f: F) where F: FnOnce() {
+        if self.last_run.elapsed() >= self.duration {
+            f();
+            self.last_run = Instant::now();
+        }
+    }
+}