Add compatibility with Linkart mod

src/main/java/audaki/cart_engine/AudakiCartEngine.java

@@ -0,0 +1,22 @@
+package audaki.cart_engine;
+
+import net.fabricmc.api.ModInitializer;
+import net.minecraft.entity.vehicle.AbstractMinecartEntity;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Function;
+
+public class AudakiCartEngine implements ModInitializer {
+    public static List<Function<AbstractMinecartEntity, Boolean>> CART_CHECK_MODIFIED_ENGINE = new ArrayList<>();
+
+    // Function should take one AbstractMinecartEntity. Return true to force
+    // modified speed logic, false to force vanilla speed logic, and null
+    // otherwise.
+    public static void registerModifiedEngineCheck(Function<AbstractMinecartEntity, Boolean> cartChecker) {
+        CART_CHECK_MODIFIED_ENGINE.add(cartChecker);
+    }
+
+    public void onInitialize() {
+    }
+}

src/main/java/audaki/cart_engine/mixin/AbstractMinecartEntityMixin.java

@@ -1,5 +1,6 @@
 package audaki.cart_engine.mixin;
 
+import audaki.cart_engine.AudakiCartEngine;
 import com.mojang.datafixers.util.Pair;
 import net.minecraft.block.AbstractRailBlock;
 import net.minecraft.block.BlockState;
@@ -28,6 +29,7 @@
 import java.util.List;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.function.BiFunction;
+import java.util.function.Function;
 import java.util.function.Supplier;
 
 @Mixin(AbstractMinecartEntity.class) // lower value, higher priority - apply first so other mods can still mixin
@@ -69,16 +71,34 @@ private static RailShape getRailShape(BlockState state) {
 
     @Inject(at = @At("HEAD"), method = "moveOnRail", cancellable = true)
     protected void moveOnRailOverwrite(BlockPos pos, BlockState state, CallbackInfo ci) {
+        // Loop through checks registered by other mods
+        Boolean shouldUseModifiedEngine = null;
+        for (Function<AbstractMinecartEntity, Boolean> cartChecker : AudakiCartEngine.CART_CHECK_MODIFIED_ENGINE) {
+            shouldUseModifiedEngine = cartChecker.apply((AbstractMinecartEntity) (Object) this);
+            // Check if the modified engine is required/suppressed
+            if (shouldUseModifiedEngine != null) {
+                break;
+            }
+        }
 
-        // We only change logic for rideable minecarts so we don't break hopper/chest minecart creations
-        if (this.getMinecartType() != Type.RIDEABLE) {
+        // Check if modified engine was suppressed
+        if (!shouldUseModifiedEngine) {
             return;
         }
 
-        // We only change logic when the minecart is currently being ridden by a living entity (player/villager/mob)
-        boolean hasLivingRider = this.getFirstPassenger() instanceof LivingEntity;
-        if (!hasLivingRider) {
-            return;
+        // If no mods required modified engine, we do our own logic here
+        if (shouldUseModifiedEngine == null) {
+
+            // We only change logic for rideable minecarts so we don't break hopper/chest minecart creations
+            if (this.getMinecartType() != Type.RIDEABLE) {
+                return;
+            }
+
+            // We only change logic when the minecart is currently being ridden by a living entity (player/villager/mob)
+            boolean hasLivingRider = this.getFirstPassenger() instanceof LivingEntity;
+            if (!hasLivingRider) {
+                return;
+            }
         }
 
         this.modifiedMoveOnRail(pos, state);
@@ -148,9 +168,6 @@ protected void modifiedMoveOnRail(BlockPos pos, BlockState state) {
         Supplier<Double> calculateMaxHorizontalMovementPerTick = () -> {
             double fallback = this.getMaxSpeed();
 
-            if (!this.hasPassengers())
-                return fallback;
-
             if (horizontalMomentumPerTick < vanillaMaxHorizontalMovementPerTick)
                 return fallback;
 
@@ -291,7 +308,7 @@ protected void modifiedMoveOnRail(BlockPos pos, BlockState state) {
         d = p + h * x;
         f = q + i * x;
         this.setPosition(d, e, f);
-        v = this.hasPassengers() ? 0.75D : 1.0D;
+        v = 1.0D;
 
         w = maxHorizontalMovementPerTick;
 
@@ -338,30 +355,25 @@ protected void modifiedMoveOnRail(BlockPos pos, BlockState state) {
             final double basisAccelerationPerTick = 0.021D;
             if (momentum > 0.01D) {
 
-                if (this.hasPassengers()) {
-                    // Based on a 10 ticks per second basis spent per powered block we calculate a fair acceleration per tick
-                    // due to spending less ticks per powered block on higher speeds (and even skipping blocks)
-                    final double basisTicksPerSecond = 10.0D;
-                    // Tps = Ticks per second
-                    final double tickMovementForBasisTps = 1.0D / basisTicksPerSecond;
-                    final double maxSkippedBlocksToConsider = 3.0D;
+                // Based on a 10 ticks per second basis spent per powered block we calculate a fair acceleration per tick
+                // due to spending less ticks per powered block on higher speeds (and even skipping blocks)
+                final double basisTicksPerSecond = 10.0D;
+                // Tps = Ticks per second
+                final double tickMovementForBasisTps = 1.0D / basisTicksPerSecond;
+                final double maxSkippedBlocksToConsider = 3.0D;
 
 
-                    double acceleration = basisAccelerationPerTick;
-                    final double distanceMovedHorizontally = movement.horizontalLength();
+                double acceleration = basisAccelerationPerTick;
+                final double distanceMovedHorizontally = movement.horizontalLength();
 
-                    if (distanceMovedHorizontally > tickMovementForBasisTps) {
-                        acceleration *= Math.min((1.0D + maxSkippedBlocksToConsider) * basisTicksPerSecond, distanceMovedHorizontally / tickMovementForBasisTps);
+                if (distanceMovedHorizontally > tickMovementForBasisTps) {
+                    acceleration *= Math.min((1.0D + maxSkippedBlocksToConsider) * basisTicksPerSecond, distanceMovedHorizontally / tickMovementForBasisTps);
 
-                        // Add progressively slower (or faster) acceleration for higher speeds;
-                        double highspeedFactor = 1.0D + MathHelper.clamp(-0.45D * (distanceMovedHorizontally / tickMovementForBasisTps / basisTicksPerSecond), -0.7D, 2.0D);
-                        acceleration *= highspeedFactor;
-                    }
-                    this.setVelocity(vec3d7.add(acceleration * (vec3d7.x / momentum), 0.0D, acceleration * (vec3d7.z / momentum)));
-                }
-                else {
-                    this.setVelocity(vec3d7.add(vec3d7.x / momentum * 0.06D, 0.0D, vec3d7.z / momentum * 0.06D));
+                    // Add progressively slower (or faster) acceleration for higher speeds;
+                    double highspeedFactor = 1.0D + MathHelper.clamp(-0.45D * (distanceMovedHorizontally / tickMovementForBasisTps / basisTicksPerSecond), -0.7D, 2.0D);
+                    acceleration *= highspeedFactor;
                 }
+                this.setVelocity(vec3d7.add(acceleration * (vec3d7.x / momentum), 0.0D, acceleration * (vec3d7.z / momentum)));
 
 
             } else {

src/main/resources/fabric.mod.json

@@ -24,6 +24,11 @@
   "icon": "assets/audaki_cart_engine/icon.png",
 
   "environment": "*",
+  "entrypoints": {
+    "main": [
+      "audaki.cart_engine.AudakiCartEngine"
+    ]
+  },
   "mixins": [
     "audaki_cart_engine.mixins.json"
   ],