refactor: Move loading to LoadWorld schedule

Co-authored-by: Georg Friedrich Schuppe <georg.schuppe@gmail.com>

src/lib.rs

@@ -8,7 +8,7 @@ use bevy::{
     utils::{Duration, HashMap},
 };
 use ggrs::{Config, InputStatus, P2PSession, PlayerHandle, SpectatorSession, SyncTestSession};
-use schedule_systems::save_world;
+use schedule_systems::{load_world, save_world};
 use std::{fmt::Debug, hash::Hash, marker::PhantomData, net::SocketAddr};
 use world_snapshot::RollbackSnapshots;
 
@@ -152,6 +152,10 @@ impl RollbackTypeRegistry {
 #[derive(ScheduleLabel, Debug, Hash, PartialEq, Eq, Clone)]
 pub struct ReadInputs;
 
+/// Label for the schedule which loads and overwrites a snapshot of the world.
+#[derive(ScheduleLabel, Debug, Hash, PartialEq, Eq, Clone)]
+pub struct LoadWorld;
+
 /// Label for the schedule which saves a snapshot of the current world.
 #[derive(ScheduleLabel, Debug, Hash, PartialEq, Eq, Clone)]
 pub struct SaveWorld;
@@ -186,6 +190,7 @@ impl<C: Config> Plugin for GgrsPlugin<C> {
             .add_schedule(GgrsSchedule, schedule)
             .add_schedule(ReadInputs, Schedule::new())
             .add_systems(PreUpdate, schedule_systems::run_ggrs_schedules::<C>)
+            .add_systems(LoadWorld, load_world)
             .add_systems(SaveWorld, save_world);
     }
 }

src/schedule_systems.rs

@@ -1,7 +1,7 @@
 use crate::{
     world_snapshot::{RollbackSnapshots, WorldSnapshot},
-    FixedTimestepData, GgrsSchedule, LocalInputs, LocalPlayers, PlayerInputs, ReadInputs,
-    RollbackFrameCount, RollbackTypeRegistry, SaveWorld, Session,
+    FixedTimestepData, GgrsSchedule, LoadWorld, LocalInputs, LocalPlayers, PlayerInputs,
+    ReadInputs, RollbackFrameCount, RollbackTypeRegistry, SaveWorld, Session,
 };
 use bevy::{prelude::*, utils::Duration};
 use ggrs::{
@@ -156,13 +156,15 @@ pub(crate) fn handle_requests<T: Config>(requests: Vec<GGRSRequest<T>>, world: &
                 cell.save(frame, None, Some(checksum as u128));
             }
             GGRSRequest::LoadGameState { frame, .. } => {
+                // we don't really use the buffer provided by GGRS
+                debug!("restoring snapshot for frame {frame}");
+
                 world
                     .get_resource_mut::<RollbackFrameCount>()
                     .expect("Unable to find GGRS RollbackFrameCount. Did you remove it?")
                     .0 = frame;
 
-                // we don't really use the buffer provided by GGRS
-                load_world(frame, world)
+                world.run_schedule(LoadWorld);
             }
             GGRSRequest::AdvanceFrame { inputs } => advance_frame::<T>(inputs, world),
         }
@@ -191,8 +193,11 @@ pub(crate) fn save_world(world: &mut World) {
     snapshots.0[pos] = snapshot;
 }
 
-pub(crate) fn load_world(frame: i32, world: &mut World) {
-    debug!("restoring snapshot for frame {frame}");
+pub(crate) fn load_world(world: &mut World) {
+    let frame = world
+        .get_resource::<RollbackFrameCount>()
+        .expect("Unable to find GGRS RollbackFrameCount. Did you remove it?")
+        .0;
 
     let rollback_registry = world
         .remove_resource::<RollbackTypeRegistry>()