Added Disable Ice Physics Trigger

Author: maddie480

Ahorn/lang/en_gb.lang

@@ -89,4 +89,7 @@ placements.entities.SpringCollab2020/FlagSwitchGate.tooltips.persistent=If enabl
 placements.entities.SpringCollab2020/FlagSwitchGate.tooltips.inactiveColor=The gate icon colour when not triggered yet.
 placements.entities.SpringCollab2020/FlagSwitchGate.tooltips.activeColor=The gate icon colour when triggered, but the group is not complete yet.
 placements.entities.SpringCollab2020/FlagSwitchGate.tooltips.finishColor=The gate icon colour when the group is complete.
-placements.entities.SpringCollab2020/FlagSwitchGate.tooltips.sprite=The texture for the gate block.
+placements.entities.SpringCollab2020/FlagSwitchGate.tooltips.sprite=The texture for the gate block.
+
+# Disable Ice Physics Trigger
+placements.triggers.SpringCollab2020/DisableIcePhysicsTrigger.tooltips.disableIcePhysics=Check to disable ice physics when entering the trigger. Uncheck to enable them again.

Ahorn/triggers/disableIcePhysics.jl

@@ -0,0 +1,15 @@
+module SpringCollab2020DisableIcePhysicsTrigger
+
+using ..Ahorn, Maple
+
+@mapdef Trigger "SpringCollab2020/DisableIcePhysicsTrigger" DisableIcePhysicsTrigger(x::Integer, y::Integer, 
+    width::Integer=Maple.defaultTriggerWidth, height::Integer=Maple.defaultTriggerHeight, disableIcePhysics::Bool=true)
+
+const placements = Ahorn.PlacementDict(
+    "Disable Ice Physics (Spring Collab 2020)" => Ahorn.EntityPlacement(
+        DisableIcePhysicsTrigger,
+        "rectangle"
+    )
+)
+
+end

Entities/DisableIcePhysicsTrigger.cs

@@ -0,0 +1,45 @@
+using Celeste.Mod.Entities;
+using Microsoft.Xna.Framework;
+using MonoMod.Cil;
+using System;
+
+namespace Celeste.Mod.SpringCollab2020.Entities {
+    [CustomEntity("SpringCollab2020/DisableIcePhysicsTrigger")]
+    class DisableIcePhysicsTrigger : Trigger {
+        public static void Load() {
+            IL.Celeste.Player.NormalUpdate += modPlayerNormalUpdate;
+        }
+
+        public static void Unload() {
+            IL.Celeste.Player.NormalUpdate -= modPlayerNormalUpdate;
+        }
+
+        private static void modPlayerNormalUpdate(ILContext il) {
+            ILCursor cursor = new ILCursor(il);
+
+            while (cursor.TryGotoNext(MoveType.After, instr => instr.MatchCallvirt<Level>("get_CoreMode"))) {
+                Logger.Log("SpringCollab2020/DisableIcePhysicsTrigger", $"Patching ice mode checking at {cursor.Index} in IL for Player.NormalUpdate");
+
+                cursor.EmitDelegate<Func<Session.CoreModes, Session.CoreModes>>(coreMode => {
+                    if (SpringCollab2020Module.Instance.Session.IcePhysicsDisabled) {
+                        // pretend there is no core mode, so that the ground is not slippery anymore.
+                        return Session.CoreModes.None;
+                    }
+                    return coreMode;
+                });
+            }
+        }
+
+        private bool disableIcePhysics;
+
+        public DisableIcePhysicsTrigger(EntityData data, Vector2 offset) : base(data, offset) {
+            disableIcePhysics = data.Bool("disableIcePhysics", true);
+        }
+
+        public override void OnEnter(Player player) {
+            base.OnEnter(player);
+
+            SpringCollab2020Module.Instance.Session.IcePhysicsDisabled = disableIcePhysics;
+        }
+    }
+}

SpringCollab2020Module.cs

@@ -1,11 +1,15 @@
 using Celeste.Mod.SpringCollab2020.Entities;
 using Celeste.Mod.SpringCollab2020.Triggers;
-
+using System;
+
 namespace Celeste.Mod.SpringCollab2020 {
     public class SpringCollab2020Module : EverestModule {
 
         public static SpringCollab2020Module Instance;
 
+        public override Type SessionType => typeof(SpringCollab2020Session);
+        public SpringCollab2020Session Session => (SpringCollab2020Session) _Session;
+
         public SpringCollab2020Module() {
             Instance = this;
         }
@@ -21,6 +25,7 @@ public override void Load() {
             BubbleReturnBerry.Load();
             SidewaysJumpThru.Load();
             CrystalBombDetonatorRenderer.Load();
+            DisableIcePhysicsTrigger.Load();
         }
 
         public override void LoadContent(bool firstLoad) {
@@ -40,6 +45,7 @@ public override void Unload() {
             BubbleReturnBerry.Unload();
             SidewaysJumpThru.Unload();
             CrystalBombDetonatorRenderer.Unload();
+            DisableIcePhysicsTrigger.Unload();
         }
 
         public override void PrepareMapDataProcessors(MapDataFixup context) {

SpringCollab2020Session.cs

@@ -0,0 +1,6 @@
+
+namespace Celeste.Mod.SpringCollab2020 {
+    public class SpringCollab2020Session : EverestModuleSession {
+        public bool IcePhysicsDisabled { get; set; } = false;
+    }
+}