Merge #482

482: Attempt to Fix Multiplayer Desync r=zicklag a=zicklag

This is based on the guess that the desync came from the lack of determinism in the scenario when you grab an item while touching multiple items, and it isn't necessarily specified which one you pick up.

Co-authored-by: Zicklag <[email protected]>

src/player/state/states/idle.rs

@@ -26,7 +26,7 @@ pub fn player_state_transition(
 pub fn handle_player_state(
     mut commands: Commands,
     player_inputs: Res<PlayerInputs>,
-    items: Query<(Option<&Parent>, &KinematicBody), (With<Item>, Without<PlayerIdx>)>,
+    items: Query<(Option<&Parent>, &Rollback), With<Item>>,
     mut players: Query<(
         Entity,
         &PlayerState,
@@ -62,16 +62,22 @@ pub fn handle_player_state(
         if control.grab_just_pressed {
             // If we don't have an item
             if !has_item {
-                // For each actor colliding with the player
-                'colliders: for collider in collision_world.actor_collisions(player_ent) {
-                    // If this is an item
-                    if let Ok((.., item_body)) = items.get(collider) {
-                        if !item_body.is_deactivated {
-                            commands
-                                .add(PlayerSetInventoryCommand::new(player_ent, Some(collider)));
-                            break 'colliders;
-                        }
-                    }
+                let mut colliders = collision_world
+                    // Get all things colliding with the player
+                    .actor_collisions(player_ent)
+                    .into_iter()
+                    // Filter out anything not an item
+                    .filter_map(|ent| items.get(ent).ok().map(|x| (ent, x)))
+                    // Filter out any items that are being held by another player
+                    .filter(|(_ent, (parent, _))| parent.is_none())
+                    .collect::<Vec<_>>();
+
+                // Sort the items to provide deterministic item selection if we hare touching multiples
+                colliders.sort_by_key(|(_, (_, rollback))| rollback.id());
+
+                // Grab the first item we are touching
+                if let Some((item, _)) = colliders.get(0) {
+                    commands.add(PlayerSetInventoryCommand::new(player_ent, Some(*item)));
                 }
 
             // If we are already carrying an item

src/player/state/states/midair.rs

@@ -19,7 +19,7 @@ pub fn player_state_transition(mut players: Query<(&mut PlayerState, &KinematicB
 pub fn handle_player_state(
     mut commands: Commands,
     player_inputs: Res<PlayerInputs>,
-    items: Query<(Option<&Parent>, &KinematicBody), (With<Item>, Without<PlayerIdx>)>,
+    items: Query<(Option<&Parent>, &Rollback), With<Item>>,
     mut players: Query<(
         Entity,
         &PlayerState,
@@ -53,17 +53,23 @@ pub fn handle_player_state(
 
         // If we are grabbing
         if control.grab_just_pressed {
-            // If we don't have an item
             if !has_item {
-                // For each actor colliding with the player
-                'colliders: for collider in collision_world.actor_collisions(player_ent) {
-                    if let Ok((.., item_body)) = items.get(collider) {
-                        if !item_body.is_deactivated {
-                            commands
-                                .add(PlayerSetInventoryCommand::new(player_ent, Some(collider)));
-                            break 'colliders;
-                        }
-                    }
+                let mut colliders = collision_world
+                    // Get all things colliding with the player
+                    .actor_collisions(player_ent)
+                    .into_iter()
+                    // Filter out anything not an item
+                    .filter_map(|ent| items.get(ent).ok().map(|x| (ent, x)))
+                    // Filter out any items that are being held by another player
+                    .filter(|(_ent, (parent, _))| parent.is_none())
+                    .collect::<Vec<_>>();
+
+                // Sort the items to provide deterministic item selection if we hare touching multiples
+                colliders.sort_by_key(|(_, (_, rollback))| rollback.id());
+
+                // Grab the first item we are touching
+                if let Some((item, _)) = colliders.get(0) {
+                    commands.add(PlayerSetInventoryCommand::new(player_ent, Some(*item)));
                 }
 
             // If we are already carrying an item

src/player/state/states/walk.rs

@@ -27,7 +27,7 @@ pub fn player_state_transition(
 pub fn handle_player_state(
     mut commands: Commands,
     player_inputs: Res<PlayerInputs>,
-    items: Query<(Option<&Parent>, &KinematicBody), (With<Item>, Without<PlayerIdx>)>,
+    items: Query<(Option<&Parent>, &Rollback), With<Item>>,
     mut players: Query<(
         Entity,
         &PlayerState,
@@ -63,17 +63,18 @@ pub fn handle_player_state(
         if control.grab_just_pressed {
             // If we don't have an item
             if !has_item {
-                // For each actor colliding with the player
-                'colliders: for collider in collision_world.actor_collisions(player_ent) {
-                    // If this is an item
-                    if let Ok((.., item_body)) = items.get(collider) {
-                        if !item_body.is_deactivated {
-                            commands
-                                .add(PlayerSetInventoryCommand::new(player_ent, Some(collider)));
-                            break 'colliders;
-                        }
-                    }
-                }
+                let mut colliders = collision_world
+                    // Get all things colliding with the player
+                    .actor_collisions(player_ent)
+                    .into_iter()
+                    // Filter out anything not an item
+                    .filter_map(|ent| items.get(ent).ok().map(|x| (ent, x)))
+                    // Filter out any items that are being held by another player
+                    .filter(|(_ent, (parent, _))| parent.is_none())
+                    .collect::<Vec<_>>();
+
+                // Sort the items to provide deterministic item selection if we hare touching multiples
+                colliders.sort_by_key(|(_, (_, rollback))| rollback.id());
 
             // If we are already carrying an item
             } else {