Hurt crammed mobs by 6 at the max entity cramming limit

Mobs only drew the cramming random and never took damage, so a crowd was never thinned. Vanilla's LivingEntity.pushEntities hurts a mob by 6 on a quarter of the ticks while max_entity_cramming or more non-riding entities are pushable around it.

crates/horizon-client/examples/probe/mob_ai_probe.rs

@@ -1121,6 +1121,7 @@ pub fn main() -> horizon_client::Result<()> {
                     biomes: &biomes,
                     mob_griefing: true,
                     mob_drops: true,
+                    max_entity_cramming: 24,
                     difficulty: LocalDifficulty::new(s.difficulty, world.day_time, 0, 0.0),
                     end: false,
                     world_seed: 0,

crates/horizon-client/src/game/creatures.rs

@@ -456,6 +456,7 @@ impl Game<'_> {
             biomes: self.res.biomes(),
             mob_griefing: self.ui.rules.bool("mob_griefing"),
             mob_drops: self.ui.rules.bool("mob_drops"),
+            max_entity_cramming: self.ui.rules.int("max_entity_cramming"),
             end: self.dim == Dim::End,
             world_seed: self.level.seed,
             sea_level: if self.dim == Dim::Nether { 32 } else { 63 },
@@ -4561,6 +4562,7 @@ pub(super) fn damage_type(kind: horizon_client::mobs::DamageKind, player: bool)
         K::SonicBoom => "minecraft:sonic_boom",
         K::Freeze => "minecraft:freeze",
         K::OutOfWorld => "minecraft:out_of_world",
+        K::Cramming => "minecraft:cramming",
     }
 }
 /// A Horizon item stack as a loot stack (id, count, damage, enchantments).

crates/horizon-client/src/mobs.rs

@@ -538,6 +538,8 @@ pub enum DamageKind {
     Freeze,
     /// `fell_out_of_world`: below the world's floor.
     OutOfWorld,
+    /// `cramming`: too many entities in one place (`maxEntityCramming`).
+    Cramming,
 }
 /// A damage source: its type, the attacking entity and where it came from.
 #[derive(Clone, Copy, Debug)]
@@ -616,6 +618,7 @@ impl Damage {
                 | DamageKind::SonicBoom
                 | DamageKind::Freeze
                 | DamageKind::OutOfWorld
+                | DamageKind::Cramming
         )
     }
     pub fn is_fire(&self) -> bool {
@@ -642,6 +645,7 @@ impl Damage {
                 | DamageKind::InWall
                 | DamageKind::Freeze
                 | DamageKind::OutOfWorld
+                | DamageKind::Cramming
         )
     }
     pub fn is_projectile(&self) -> bool {
@@ -1811,6 +1815,8 @@ pub struct MobWorld<'a> {
     pub mob_griefing: bool,
     /// The `mob_drops` game rule (`shouldDropLoot`).
     pub mob_drops: bool,
+    /// The `max_entity_cramming` game rule.
+    pub max_entity_cramming: i32,
     /// `getCurrentDifficultyAt` at the mob being ticked (near the player
     /// outside the mob tick).
     pub difficulty: spawning::LocalDifficulty,
@@ -2183,6 +2189,7 @@ impl Mob {
                     | DamageKind::InWall
                     | DamageKind::Thorns
                     | DamageKind::OutOfWorld
+                    | DamageKind::Cramming
                     | DamageKind::Generic
             )
     }

crates/horizon-client/src/mobs/ai.rs

@@ -1058,7 +1058,8 @@ fn push_entities(m: &mut Mob, w: &MobWorld, events: &mut Vec<MobEvent>) {
         && m.species() != Species::Shulker
         && !on_climbable(m, w)
         && (m.species() != Species::Creaking || super::creaking::can_move(m));
-    let mut targets: Vec<(Who, Vec3)> = Vec::new();
+    // Each with whether it rides a vehicle (`Entity.isPassenger`).
+    let mut targets: Vec<(Who, Vec3, bool)> = Vec::new();
     if let Some(p) = &w.player
         // Entity.push: passengers of the same vehicle never push each other.
         && m.rider.is_none()
@@ -1066,21 +1067,27 @@ fn push_entities(m: &mut Mob, w: &MobWorld, events: &mut Vec<MobEvent>) {
         && !p.spectator
         && p.bounds.intersects(bounds)
     {
-        targets.push((Who::Player, p.position));
+        targets.push((Who::Player, p.position, p.passenger));
     }
     for o in w.others_near(bounds) {
         if o.id != m.id && o.alive && o.pushable && o.bounds.intersects(bounds) {
-            targets.push((Who::Mob(o.id), o.position));
+            targets.push((Who::Mob(o.id), o.position, o.passenger));
         }
     }
     // EntitySelector.pushableBy(this): the teams' collision rules.
     let own = w.teams.of(Who::Mob(m.id));
-    targets.retain(|(who, _)| crate::scoreboard::pushable_by(own, w.teams.of(*who), true));
-    // Cramming (maxEntityCramming 24).
-    if targets.len() > 23 {
-        let _ = m.random.next_int_bound(4);
+    targets.retain(|(who, ..)| crate::scoreboard::pushable_by(own, w.teams.of(*who), true));
+    // Cramming: a quarter of the ticks spent with `maxEntityCramming` or more
+    // others around that are not riding anything hurts it by 6.
+    let limit = w.max_entity_cramming;
+    if limit > 0
+        && targets.len() as i64 > i64::from(limit) - 1
+        && m.random.next_int_bound(4).unwrap_or(1) == 0
+        && targets.iter().filter(|t| !t.2).count() as i64 > i64::from(limit) - 1
+    {
+        m.damage(6.0, Damage::of(DamageKind::Cramming));
     }
-    for (who, at) in targets {
+    for (who, at, _) in targets {
         // Warden.doPush: touching it angers it, then the push itself.
         if m.species() == Species::Warden {
             super::warden::do_push(m, w, who, events);