Getting Started with MMDR

Welcome to MMDR! This guide will walk you through installation, setup, and your first development session with instant hot reloading.

Table of Contents

1. Installation
2. First Launch
3. Setting Up Hot Reload
4. Your First Hot Reload
5. Using the Debug Console
6. Using the Inspector
7. Recording Your First Test
8. Troubleshooting

Installation

Prerequisites

Before installing MMDR, ensure you have:

• ✅ Minecraft 1.20.4
• ✅ Fabric Loader 0.15.3 or higher
• ✅ Fabric API mod
• ✅ Java 17 or higher
• ✅ A Java IDE (IntelliJ IDEA, Eclipse, or VS Code)

Download and Install

Option 1: Build from Source

# Clone the repository
git clone https://github.com/yourusername/MMDR.git
cd MMDR

# Build the mod
./gradlew build

# The built JAR will be in build/libs/

Option 2: Download Release

1. Go to Releases
2. Download the latest mmdr-x.x.x.jar

Install the Mod

1. Navigate to your Minecraft directory:

• Windows: %APPDATA%\.minecraft
• macOS: ~/Library/Application Support/minecraft
• Linux: ~/.minecraft

1. Place mmdr-x.x.x.jar in the mods folder

2. Launch Minecraft with the Fabric profile

First Launch

Verify Installation

1. Launch Minecraft with the Fabric profile
2. Wait for the main menu to load
3. Press ` (backtick key, usually above Tab)
4. You should see the MMDR Debug Console: ```text ╔════════════════════════════════════════════════════════╗ ║ MMDR Debug Console v1.0.0 ║ ║ Type Java/Groovy code to execute. Press ESC to close. ║ ╚════════════════════════════════════════════════════════╝

```

1. Type println("Hello MMDR!") and press Enter
2. You should see the output: Hello MMDR!

If the console opens, installation was successful! ✅

Configuration File

On first launch, MMDR creates a configuration file at:

.minecraft/config/mmdr-config.json

You can edit this file to customize MMDR’s behavior.

Setting Up Hot Reload

Hot reload requires MMDR to watch your mod’s compiled class files.

Step 1: Configure Your IDE

IntelliJ IDEA:

1. Go to Settings → Build, Execution, Deployment → Compiler
2. Enable “Build project automatically”
3. Enable “Compile independent modules in parallel”
4. Click Apply

Eclipse:

1. Go to Window → Preferences → General → Workspace
2. Enable “Build automatically”
3. Click Apply

Step 2: Configure Watch Paths

MMDR needs to know where your compiled classes are located.

Edit .minecraft/config/mmdr-config.json:

{
  "hotReloadEnabled": true,
  "additionalWatchPaths": [
    "/path/to/your/mod/build/classes/java/main",
    "/path/to/your/mod/out/production/classes"
  ]
}

Example paths:

• IntelliJ: C:/Projects/MyMod/out/production/classes
• Gradle: C:/Projects/MyMod/build/classes/java/main
• Eclipse: C:/Projects/MyMod/bin

Step 3: Verify Hot Reload is Active

1. Launch Minecraft with your mod
2. Open the console (`)
3. Type: /reload status
4. You should see: ```text

Hot Reload: ✓ ACTIVE Watching: 2 directories Reloaded: 0 classes

---
### Your First Hot Reload

Let's modify some code and see it update instantly!

### Step 1: Create a Test Class

In your mod, create a simple class:
```Java

package com.example.mymod;

public class HotReloadTest {
    public static String getMessage() {
        return "Original message";
    }
}

Step 2: Use It In-Game

1. Launch Minecraft
2. Open the debug console (`)
3. Execute: ```groovy

import com.example.mymod.HotReloadTest println(HotReloadTest.getMessage())

4. You should see: `Original message`

### Step 3: Modify the Code
In your IDE, change the message:
```Java
public static String getMessage() {
    return "HOT RELOADED! 🔥"; // Changed!
}

Save the file (Ctrl+S / Cmd+S)

Step 4: See the Changes

In the console, run the same code again:

println(HotReloadTest.getMessage())

You should now see: HOT RELOADED! 🔥

No restart needed! ✨

Using the Debug Console

The console is a powerful REPL (Read-Eval-Print-Loop) environment.

Basic Commands

// Get the Minecraft client instance
mc

// Get the player
mc.player

// Get the world
mc.world

// Print player position
println(mc.player.getPos())

// Teleport player
mc.player.setPosition(0, 100, 0)

// Give items
import net.minecraft.item.Items
import net.minecraft.item.ItemStack
mc.player.giveItemStack(new ItemStack(Items.DIAMOND, 64))

// Change time
mc.world.setTimeOfDay(6000)  // Noon
mc.world.setTimeOfDay(18000) // Midnight

// Weather
mc.world.setWeather(0, 0, true, false)  // Clear

Special Commands

Commands starting with / are MMDR-specific:

/help       // Show all commands
/clear      // Clear console output
/vars       // List all variables
/reload     // Manually reload a class
/imports    // Show auto-imports

Variables

The console provides these pre-defined variables:

Command History

• Up Arrow: Previous command
• Down Arrow: Next command
• Ctrl+R: Search history

Multi-line Input

For complex code, use multi-line mode:

// Define a function
def teleportRandomly() {
    def x = (Math.random() - 0.5) * 1000
    def z = (Math.random() - 0.5) * 1000
    mc.player.setPosition(x, 100, z)
}

// Call it
teleportRandomly()

Using the Inspector

The inspector shows detailed information about blocks and entities.

Basic Usage

1. Press F3 to enable the inspector
2. Look at any block or entity
3. Information appears on the left side of the screen

   Keyboard Shortcuts

   | Key | Function| |—|—————————| |F3 |Toggle inspector / cycle modes | |F4 |Toggle NBT data display | |F5 |Toggle packet monitor | |F6 |Toggle event listeners | |F7 |Toggle performance metrics |

Inspector Modes

BASIC Mode:

• Block/entity type
• Position
• Basic properties

DETAILED Mode:

• All basic info
• NBT data
• Block state properties
• Entity health/velocity

ADVANCED Mode:

• Everything from detailed
• Network packets
• Event listeners
• Performance metrics

Reading NBT Data

When NBT display is enabled (F4), you’ll see:

§6§lNBT Data:
§e{
  §eid§7: §b"minecraft:chest"
  §eitems§7: [
    §e{
      §eSlot§7: §b0
      §eid§7: §a"minecraft:diamond"
      §eCount§7: §b64
    §e}
  §e]
§e}

Color codes:

• 🟡 Yellow: Keys
• 🔵 Blue: Numbers
• 🟢 Green: Strings
• 🟣 Purple: Booleans

Recording Your First Test

The test harness can automatically generate unit tests from your gameplay.

Step 1: Start Recording

1. Press F9 to start recording
2. You’ll see a message: [MMDR] Recording started
3. A red dot appears in the corner

   Step 2: Perform Actions

   Do some actions in the game:

• Break some blocks
• Place some blocks
• Use items
• Move around

  Step 3: Stop Recording

  1. Press F9 again
  2. You’ll see: [MMDR] Recording stopped - X actions recorded

Step 4: Generate Test Code

Open the console and run:

MMDR.getTestHarness().generateTestCodeFromCurrent("MyFirstTest")

Step 5: View the Generated Test

The test is saved to:

.minecraft/mmdr_recordings/MyFirstTest.java

Example generated code:

package com.example.tests;

import org.junit.jupiter.api.*;
import static org.junit.jupiter.api.Assertions.*;

public class MyFirstTest {
    
    @Test
    public void testRecordedSession() {
        // Action 0: Break block at (10, 64, 20)
        player.breakBlock(new BlockPos(10, 64, 20));
        
        // Action 1: Place block at (11, 64, 20)
        player.placeBlock(new BlockPos(11, 64, 20), Blocks.STONE);
        
        // Action 2: Move to 12.50, 64.00, 21.30
        player.setPosition(12.50, 64.00, 21.30);
    }
}

Troubleshooting

Console Won’t Open

Problem: Pressing ` does nothing

Solutions:

1. Check for key conflicts in Options → Controls
2. Verify MMDR is installed: Look for MMDR in the Mods menu
3. Check logs/latest.log for errors
4. Try rebinding the key in controls

Hot Reload Not Working

Problem: Code changes don’t appear in-game

Solutions:

1. Verify IDE is compiling:
   • IntelliJ: Check the “Build” output panel
   • Eclipse: Check “Problems” view
   • Look for .class files in your output directory
2. Check watch paths: ```groovy

// In console: MMDR.getHotReloadManager().isRunning() // Should return: true

3. **Verify the class isn't excluded:**
- Check `excludedPackages` in config
- Minecraft classes (`net.minecraft.*`) can't be reloaded

4. **Check the logs:**
```text

[MMDR] Detected change in class: com.example.MyClass
[MMDR] Successfully reloaded 1 classe(s)

Inspector Shows Nothing

Problem: Inspector overlay is blank

Solutions:

1. Look directly at a block or entity
2. Toggle modes with F3
3. Check that inspectorEnabled: true in config
4. Restart Minecraft

Performance Issues

Problem: Game runs slowly with MMDR

Solutions:

1. Disable unused features:

   {
     "hotReloadEnabled": false,
     "inspectorShowPackets": false
   }
   

2. Increase file watch interval:

   {
     "fileWatchInterval": 2000
   }
   

3. Allocate more memory:

   Add to JVM arguments: -Xmx4G

Class Reload Fails

Problem: Error message when reloading a class

Common causes:

1. Syntax errors: Fix the error and save again
2. Changed method signatures: Some changes require restart
3. Static initialization: Static blocks run again on reload
4. Class dependencies: Dependent classes may need reload too

Workaround:

// Force reload dependencies
/reload com.example.DependentClass

Next Steps

Now that you’re set up, explore more features:

• 📖 Hot Reload Guide - Advanced hot reload techniques
• 💻 Console Guide - Master the debug console
• 🔍 Inspector Guide - Deep dive into inspection
• 📚 API Reference - Complete API documentation

Getting Help

• Documentation: Check the docs folder
• Issues: GitHub Issues
• Discord: Join our server (we don't have one yet)
• Discussions: GitHub Discussions

Happy modding with MMDR! 🚀