Added first version.

README.md

@@ -1,9 +1,3 @@
-# Fabric Example Mod
+# Speed Carts
 
-## Setup
+This mod adds the ability to control minecarts with signs.
-
-For setup instructions please see the [fabric wiki page](https://fabricmc.net/wiki/tutorial:setup) that relates to the IDE that you are using.
-
-## License
-
-This template is available under the CC0 license. Feel free to learn from it and incorporate it in your own projects.

gradle.properties

@@ -9,8 +9,8 @@ org.gradle.jvmargs=-Xmx1G
 
 # Mod Properties
 	mod_version = 1.0.0
-	maven_group = com.example
+	maven_group = nl.andrewlalis
-	archives_base_name = fabric-example-mod
+	archives_base_name = speed-carts
 
 # Dependencies
 	fabric_version=0.37.0+1.17

src/main/java/net/fabricmc/example/ExampleMod.java

@@ -1,14 +0,0 @@
-package net.fabricmc.example;
-
-import net.fabricmc.api.ModInitializer;
-
-public class ExampleMod implements ModInitializer {
-	@Override
-	public void onInitialize() {
-		// This code runs as soon as Minecraft is in a mod-load-ready state.
-		// However, some things (like resources) may still be uninitialized.
-		// Proceed with mild caution.
-
-		System.out.println("Hello Fabric world!");
-	}
-}

src/main/java/net/fabricmc/example/mixin/ExampleMixin.java

@@ -1,15 +0,0 @@
-package net.fabricmc.example.mixin;
-
-import net.minecraft.client.gui.screen.TitleScreen;
-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.CallbackInfo;
-
-@Mixin(TitleScreen.class)
-public class ExampleMixin {
-	@Inject(at = @At("HEAD"), method = "init()V")
-	private void init(CallbackInfo info) {
-		System.out.println("This line is printed by an example mod mixin!");
-	}
-}

src/main/java/nl/andrewlalis/speed_carts/SpeedCarts.java

@@ -0,0 +1,10 @@
+package nl.andrewlalis.speed_carts;
+
+import net.fabricmc.api.ModInitializer;
+
+public class SpeedCarts implements ModInitializer {
+	@Override
+	public void onInitialize() {
+		System.out.println("Speed Carts initialized.");
+	}
+}

src/main/java/nl/andrewlalis/speed_carts/mixin/AbstractMinecartMixin.java

@@ -0,0 +1,181 @@
+package nl.andrewlalis.speed_carts.mixin;
+
+import com.mojang.datafixers.util.Pair;
+import net.minecraft.block.BlockState;
+import net.minecraft.block.entity.SignBlockEntity;
+import net.minecraft.block.enums.RailShape;
+import net.minecraft.entity.Entity;
+import net.minecraft.entity.EntityType;
+import net.minecraft.entity.player.PlayerEntity;
+import net.minecraft.entity.vehicle.AbstractMinecartEntity;
+import net.minecraft.sound.SoundCategory;
+import net.minecraft.sound.SoundEvent;
+import net.minecraft.state.property.Properties;
+import net.minecraft.text.Text;
+import net.minecraft.util.DyeColor;
+import net.minecraft.util.Identifier;
+import net.minecraft.util.math.BlockPos;
+import net.minecraft.util.math.Direction;
+import net.minecraft.util.math.Vec3d;
+import net.minecraft.util.math.Vec3i;
+import net.minecraft.world.World;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+
+/**
+ * Mixin which overrides the default minecart behavior so that we can define a
+ * changeable speed, and check for updates.
+ */
+@Mixin(AbstractMinecartEntity.class)
+public abstract class AbstractMinecartMixin extends Entity {
+	private static final double DEFAULT_SPEED = 8.0;
+	private static final double MIN_SPEED = 1.0;
+	private static final double MAX_SPEED = 128.0;
+	private static final long SPEED_UPDATE_COOLDOWN = 20 * 3;
+
+	/**
+	 * The currently-set maximum speed, in blocks per second.
+	 */
+	private double maxSpeedBps = DEFAULT_SPEED;
+
+	/**
+	 * The last time (in game ticks) that the speed was updated.
+	 */
+	private long lastSpeedUpdate = 0;
+
+	/**
+	 * The position of the block which was last responsible for updating the
+	 * cart's speed.
+	 */
+	private BlockPos lastUpdatedFrom = null;
+
+	@Shadow
+	public abstract Vec3d snapPositionToRail(double x, double y, double z);
+
+	@Shadow
+	private static Pair<Vec3i, Vec3i> getAdjacentRailPositionsByShape(RailShape shape) {
+		return null;
+	}
+
+	@Shadow
+	protected abstract double getMaxOffRailSpeed();
+
+	@Inject(at = @At("HEAD"), method = "getMaxOffRailSpeed", cancellable = true)
+	public void getMaxOffRailSpeedOverwrite(CallbackInfoReturnable<Double> cir) {
+		cir.setReturnValue(this.maxSpeedBps / 20.0);
+	}
+
+	@Shadow
+	protected abstract void applySlowdown();
+
+	@Shadow
+	protected abstract boolean willHitBlockAt(BlockPos pos);
+
+	public AbstractMinecartMixin(EntityType<?> type, World world) {
+		super(type, world);
+	}
+
+	@Shadow
+	protected abstract void moveOnRail(BlockPos pos, BlockState state);
+
+	@Shadow public abstract Direction getMovementDirection();
+
+	@Inject(at = @At("HEAD"), method = "moveOnRail", cancellable = true)
+	public void moveOnRailOverwrite(BlockPos pos, BlockState state, CallbackInfo ci) {
+		this.updateForSpeedModifiers(pos);
+	}
+
+	/**
+	 * Checks for any speed modifiers (signs, blocks, etc.) and attempts to
+	 * apply their effects to the cart. It does this by iterating over a list of
+	 * possible positions for blocks which are considered speed modifiers, and
+	 * then if a valid speed modifier is found, the cart's speed is updated.
+	 * @param pos The cart's current position.
+	 */
+	private void updateForSpeedModifiers(BlockPos pos) {
+		// Quit if the cart is not moving, and set its speed to default.
+		if (this.getVelocity().length() == 0) {
+			this.maxSpeedBps = DEFAULT_SPEED;
+			return;
+		}
+
+		for (var position : this.getPositionsToCheck(pos)) {
+			if (
+				this.world.getBlockEntity(position) instanceof SignBlockEntity sign &&
+				(!sign.getPos().equals(this.lastUpdatedFrom) || this.world.getTime() > this.lastSpeedUpdate + SPEED_UPDATE_COOLDOWN)
+			) {
+				var state = this.world.getBlockState(position);
+				var dir = (Direction) state.getEntries().get(Properties.HORIZONTAL_FACING);
+				// Only allow free-standing signs or those facing the cart.
+				if (dir == null || dir.equals(this.getMovementDirection().getOpposite())) {
+					if (this.updateSpeedForSign(sign)) return;
+				}
+			}
+		}
+	}
+
+	/**
+	 * Attempts to update the cart's speed according to a sign.
+	 * @param sign The sign that contains speed information.
+	 * @return True if the cart's speed was updated, or false otherwise.
+	 */
+	private boolean updateSpeedForSign(SignBlockEntity sign) {
+		Text text = sign.getTextOnRow(0, false);
+		String s = text.asString();
+		try {
+			double speed = Double.parseDouble(s);
+			if (speed >= MIN_SPEED && speed <= MAX_SPEED) {
+				this.maxSpeedBps = speed;
+				this.lastSpeedUpdate = this.world.getTime();
+				this.lastUpdatedFrom = sign.getPos();
+				if (this.hasPlayerRider()) {
+					PlayerEntity player = (PlayerEntity) this.getFirstPassenger();
+					if (player != null) {
+						player.playSound(new SoundEvent(new Identifier("block.note_block.bell")), SoundCategory.PLAYERS, 1.0f, 1.0f);
+					}
+				}
+				return true;
+			} else {
+				sign.setTextOnRow(0, Text.of("Invalid speed!"));
+				sign.setTextOnRow(1, Text.of("Min: " + MIN_SPEED));
+				sign.setTextOnRow(2, Text.of("Max: " + MAX_SPEED));
+				sign.setGlowingText(true);
+				sign.setTextColor(DyeColor.RED);
+			}
+		} catch (NumberFormatException e) {
+			// Do nothing if no value could be parsed.
+		}
+		return false;
+	}
+
+	/**
+	 * Gathers a list of all block positions to check for signs that may affect
+	 * the cart's speed.
+	 * @param pos The cart's block position.
+	 * @return A collection of positions to check.
+	 */
+	private Collection<BlockPos> getPositionsToCheck(BlockPos pos) {
+		// Compute the number of blocks we have to check ahead.
+		// This accounts for speeds greater than 1 block per tick.
+		int blockRange = Math.max(1, (int) Math.ceil(this.maxSpeedBps / 20));
+		List<BlockPos> positionsToCheck = new ArrayList<>(6 * blockRange);
+		for (int i = 0; i < blockRange; i++) {
+			positionsToCheck.add(pos.north());
+			positionsToCheck.add(pos.south());
+			positionsToCheck.add(pos.east());
+			positionsToCheck.add(pos.west());
+			positionsToCheck.add(pos.up());
+			positionsToCheck.add(pos.down());
+			pos = pos.add(this.getMovementDirection().getVector());
+		}
+		return positionsToCheck;
+	}
+}

src/main/resources/fabric.mod.json

@@ -1,16 +1,16 @@
 {
   "schemaVersion": 1,
-  "id": "modid",
+  "id": "speed-carts",
   "version": "${version}",
 
-  "name": "Example Mod",
+  "name": "Speed Carts",
-  "description": "This is an example description! Tell everyone what your mod is about!",
+  "description": "Increases the speed of minecarts.",
   "authors": [
-    "Me!"
+    "Andrew Lalis"
   ],
   "contact": {
-    "homepage": "https://fabricmc.net/",
+    "homepage": "https://andrewl.nl/",
-    "sources": "https://github.com/FabricMC/fabric-example-mod"
+    "sources": "https://github.com/andrewlalis/SpeedCarts"
   },
 
   "license": "CC0-1.0",
@@ -19,7 +19,7 @@
   "environment": "*",
   "entrypoints": {
     "main": [
-      "net.fabricmc.example.ExampleMod"
+      "nl.andrewlalis.speed_carts.SpeedCarts"
     ]
   },
   "mixins": [

src/main/resources/modid.mixins.json

@@ -1,12 +1,16 @@
 {
   "required": true,
   "minVersion": "0.8",
-  "package": "net.fabricmc.example.mixin",
+  "package": "nl.andrewlalis.speed_carts.mixin",
   "compatibilityLevel": "JAVA_16",
   "mixins": [
+    "AbstractMinecartMixin"
   ],
   "client": [
-    "ExampleMixin"
+    "AbstractMinecartMixin"
+  ],
+  "server": [
+    "AbstractMinecartMixin"
   ],
   "injectors": {
     "defaultRequire": 1