Changes ScheduleRunnerPlugin RunMode::Loop to run on fixed interval (#…

…233)

* Changes ScheduleRunnerPlugin RunMode::Loop to run on fixed interval

* fix formatting

crates/bevy_app/src/schedule_runner.rs

@@ -4,7 +4,10 @@ use crate::{
  event::{EventReader, Events},
  plugin::Plugin,
 };
-use std::{thread, time::Duration};
+use std::{
+ thread,
+ time::{Duration, Instant},
+};
 
 /// Determines the method used to run an [App]'s `Schedule`
 #[derive(Copy, Clone, Debug)]
@@ -51,6 +54,8 @@ impl Plugin for ScheduleRunnerPlugin {
  app.schedule.run(&mut app.world, &mut app.resources);
  }
  RunMode::Loop { wait } => loop {
+ let start_time = Instant::now();
+
  if let Some(app_exit_events) = app.resources.get_mut::<Events<AppExit>>() {
  if app_exit_event_reader.latest(&app_exit_events).is_some() {
  break;
@@ -65,8 +70,13 @@ impl Plugin for ScheduleRunnerPlugin {
  }
  }
 
+ let end_time = Instant::now();
+
  if let Some(wait) = wait {
- thread::sleep(wait);
+ let exe_time = end_time - start_time;
+ if exe_time < wait {
+ thread::sleep(wait - exe_time);
+ }
  }
  },
  }