Fix custom elytra flight

Fixes #152

fabric-entity-events-v1/src/main/java/net/fabricmc/fabric/mixin/entity/event/IItemStackExtensionMixin.java

@@ -0,0 +1,20 @@
+package net.fabricmc.fabric.mixin.entity.event;
+
+import net.fabricmc.fabric.api.entity.event.v1.EntityElytraEvents;
+import net.minecraft.world.entity.LivingEntity;
+import net.neoforged.neoforge.common.extensions.IItemStackExtension;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
+
+@Mixin(IItemStackExtension.class)
+public interface IItemStackExtensionMixin {
+
+    @Inject(method = "canElytraFly", at = @At("HEAD"), cancellable = true)
+    default void canElytraFly(LivingEntity entity, CallbackInfoReturnable<Boolean> cir) {
+        if (EntityElytraEvents.CUSTOM.invoker().useCustomElytra(entity, false)) {
+            cir.setReturnValue(true);
+        }
+    }
+}

fabric-entity-events-v1/src/main/resources/fabric-entity-events-v1.mixins.json

@@ -11,7 +11,7 @@
     "ServerPlayerEntityMixin",
     "elytra.LivingEntityMixin",
     "elytra.PlayerEntityMixin",
-    "IItemExtensionMixin"
+    "IItemStackExtensionMixin"
   ],
   "injectors": {
     "defaultRequire": 1,

ffapi.gradle.properties

@@ -1,7 +1,7 @@
 loom.platform=neoforge
 fabric.loom.dontRemap=true
 
-implementationVersion=2.0.20
+implementationVersion=2.0.21
 
 versionMc=1.21.1
 versionForge=21.1.57