Development

From GT New Horizons

Introduction

Everyone can contribute to GTNH in one way or another. One possible way is to improve or expand the source code of the mods.

To get started, you first need a vision for what you want to do.
If you don't have it yet, you can look through issues and try to address some.
If you do have a vision but want to hear more opinions on it, you can discuss it in a new Github issue or in Discord.

Getting started

If you found a mod that you want to edit, then create a fork of it by pressing the Fork button on its GitHub page.
After that, you can clone your fork to a local repository, import it to your IDE, and get started on development.
If you are not sure how to do something, try to look up how things similar to it were done before.

Starting from an existing repository

  1. Clone the repository.
  2. Update the buildscript automatically through ./gradlew updateBuildScript or if it doesn't work, manually with this guide.

Starting from scratch

See the ExampleMod README.md if the instructions below don't work.

  1. Unzip project starter into project directory.
  2. Replace placeholders in LICENSE-template and rename it to LICENSE, or remove LICENSE-template and put any other license you like on your code. This is an permissive OSS project and we encourage you participate in OSS movement by having permissive license like one in template. You can find out pros and cons of OSS software in this article.
  3. Ensure your project is under VCS. For example initialize git repository by running git init; git commit --message "initialized repository".
  4. Replace placeholders (edit values in gradle.properties, change example package and class names, etc.).
  5. Run ./gradlew build.
  6. Make sure to check out the rest sections of this file.
  7. You are good to go!

Next steps

  1. Run ./gradlew updateBuildScript to update the Gradle build-script for the repository.
  2. Run ./gradlew build --build-cache to build the project. The flag --build-cache makes builds faster. For more info, see documentation.
  3. If the build fails, check what was printed in console. Usually it fails because of outdated dependencies or Spotless. You can fix it with ./gradlew updateDependencies or ./gradlew spotlessApply respectively.
  4. In Eclipse / IntelliJ IDEA, import your workspace as an existing Gradle project. If the import fails, you may need to adjust the Gradle version and/or the buildscript. If you are developing for Minecraft 1.7.10, read this guide.
  5. After you made changes, test them:
    1. Build the project with ./gradlew build. You will find several jars in build/libs. What you need is the one without affixes like -dev or -api.
    2. Download the last nightly build and import it in the launcher of your choice.
    3. Replace the target mod with your version or add if it's a new one.
    4. Launch the pack and check that things work as they should.

Common issues

  • If your IDE tells you that stuff is missing even after you executed gradlew build, then try to reload Gradle.
  • You need a 64-bit Java for development. Most mods work with any Java 8-19. However, some mods now use enableModernJavaSyntaxin gradle.properties. In that case you need at least Java 11 to compile them. If you have multiple Java versions on your machine, then you may need to set the JAVA_HOME environment variable to the location of your desired Java installation and also configure it in your IDE.

Git Configuration

If you want to avoid signing commits with your real name, then please refer to the page Managing Git Identities.

Contribution Procedure

  1. Find something to contribute.
  2. Fork the needed repos.
  3. Test your changes thoroughly. If you change something, understand the changed class or method in order to understand what to test.
  4. Push code into your fork.
  5. Open a pull request against master branch and provide a description on what it changes/adds/removes. Include pictures/graphs if necessary. If there is a related issue, link it.
  6. Address review problems. Resolve merge conflicts. Wait for the final merge. During this period, your PR might be merged into dev branch manually by project admins, on a case by case basis. If that happens, your changes will go into one of the nightlies for border testings. There is no strict rules over whether this merge-into-dev will happen at all, and it's usually not needed anyway. It's however expected that the original author should fix every issues arouse during nightly testings, if any.

Please do not make multiple changes/features in a single PR, make a separate PR for each. If they depend on each other, you can leave a note in the PR's description.

If you are not sure how to fork and open pull requests, read this gist by Chaser324.

GTNH-specific Contribution Guides

  • You can find the Code of Conduct of the GTNH dev community here.
  • See which GTNH mods are supported outside of the modpack and see an overview of licenses in this spreadsheet.
  • For the GTNH Code Style guidelines please see the dedicated page Code Style.
  • For quest development, read the Quests Development Guide.
  • The StructureLib documentation can be found here. Use this for your multiblock structures.
  • To understand how chemical formulas are balanced in recipes, read Chemical Balance.

Tools

All applications that are grouped together can do about the same. This does not mean that you can pick any one of them, as they differ in functionality, style, performance and customizability. It is recommended you look at what they can do and try each one out, so you can decide which application you want to use for which use case.

Category Links
Code Editors
Integrated Development Environments (IDEs)
Image Editors
Modeling
Animation
Miscellaneous

Helpful IDEA Plugins

Additionally, if you choose JetBrains IntelliJ IDEA as your IDE, there are some plugins that can be very helpful in some ways

  • Minecraft Development: Autocompletion for mixin development, builtin NBT editor, minecraft project project type in new project window, and a bunch more small utility. Notice that for GTNH specifically you will want the fork maintained by eigenraven. We use RFG as the build tool and that one unfortunately is not compatible with the original version available on the plugin marketplace. Follow the install instructions in README of that fork.
  • ASM Bytecode Viewer: Very helpful plugin for asm development. Can also be occasionally helpful for mixin development. Notice that there are multiple plugins with similiar name and near identical purpose, with one of them being a bundled one from JetBrains. The JetBrains one is slightly wonky and doesn't display ASMified code. The plugin suggested here works perfectly and can display ASMified code. If in doubt whether you got the correct plugin, here is a direct link: https://plugins.jetbrains.com/plugin/10302-asm-bytecode-viewer To use this plugin, focus on any opened Java editor tab (either it's decompiled library class without attached source, library class with attached source, or your own source files), then click ASM Bytecode Viewer in Code menu. The action is also available via Search Everything under the same name. For your own source files, it will trigger a project build to ensure .class files are up to date.

Debugging with Eclipse

Set up launch config:

  1. Select the project you want to debug
  2. Click the drop-down menu next to the debug symbol -> Debug configurations...
  3. Select "Remote Java Application"
  4. Click "New launch configuration" (top left)
  5. Change the port to 5005
  6. Click "Apply"

Actually debug:

  1. Launch the game with --debug-jvm (I do this from the terminal)
  2. Wait until it says "Listening for transport dt_socket at address: 5005"
  3. Debug with the launch config you created (you may have to go into the debug configurations menu again, if it doesnt show up in the drop-down yet)
  4. Change to the "Debug" view (button in the top-right corner). There may be a window popping up asking if you want to go there
  5. Done!

Maven/Jenkins Selection

URL Mods
https://aidancbrady.com/mekanism/download/ Mekanism, MekanismGenerators, MekanismTools
https://api.modrinth.com/maven All Modrinth mods
https://chickenbones.net/maven/ CodeChickenCore, CodeChickenLib, EnderStorage, NotEnoughItems, Translocator, WR-CBE, ...
https://ci.rs485.network/
http://downloads.gtnewhorizons.com/Mods_for_Jenkins/ Various
https://dvs1.progwml6.com/files/maven IguanaTinkerTweaks, HungerOverhaul, Mantle, Natura, TinkersConstruct, TinkersMechworks, ...
https://files.projectredwiki.com/maven MrTJPCore, ForgeRelocation, ProjectRed
https://files.vexatos.com Are We Endgame Yet?, AsieLib, BeeSpecific, BuildcraftOilTweak, CheatyComputers, Computronics, Conventional, CustomManualTab, Don't Stub Your Toe, FactumOpus, ForecatsersBackpacks, TGregworks, ...
https://gregtech.overminddl1.com/ Various
https://immibis.com/ Advanced Machines, Advanced Repulsion Systems, AutoFood, Cloud Storage, Connected Glass, Dimensional Anchors, Immibis Core, Immibis's Macroblocks, Immibis's Microblocks, Immibis's Peripherals, InfiView, InfiniTubes, Liquid XP, RedLogic, Simple Recycling, TinyCarts, TubeStuff, ...
https://jenkins.bdew.net/maven AE2Stuff, BDLib, CoFHLib, Compacter, Computercraft, Generators, Gendustry, Mekanism, Pressure, ...
https://jenkins.dries007.net/ AutoCrafter2000, BetterFoliage, CrayCrafting, D3Backend, D3Log, GooglyEyes, GreenThumb, HoloInventory, InsiderTrading, MCLink, MineSafety, MorphAdditions, Pay2Spawn, Pay2SpawnBlocks, PlaceableTools, TapeMouse, TerraFirmaCraft, TerraFirmaStuff, TFCraft-NEIplugin, TFC-Tweaks, Thermal Expansion, TorchTools, WeepingAngels, ...
https://jenkins.ironhide.de/ CraftingUtilities, Open Modular Turrets, FloodLights, ...
http://jenkins.usrv.eu:8080/ Various
https://nexus.gtnewhorizons.com/repository/public/ Various
https://jitpack.io/ Any GitHub project
https://maven.blamejared.com/ MineTweaker3, CraftTweaker, ...
https://maven.cil.li/ AppliedEnergistics 2, BetterStorage, BloodMagic, BluePower, BuildCraft, Charset, CodeChickenCore, CodeChickenLib, CoFHCore, CoFHLib, ColoredLightsCore, ComputerCraft, CraftGuide, EnderCore, EnderIO, EnderStorage, Forestry, Forge Multipart, GalacticraftCore, GregTech, Immibis Multipart, InGameWiki, Inventory Tweaks, Mantle, Mekanism, MineFactory Reloaded, MrTJPCore, NotEnoughItems, NotEnoughKeys, OpenComputers, PowerAdvantage, QmunityLib, ProjectRed, Railcraft, RedLogic, RedstoneFlux API, RotaryCraft, RotateableBlocks, ThaumicEnergistics, TinkersConstruct, TinkersMechworks, TIS-3D, Waila, WR-CBE, ...
https://maven.covers1624.net/

https://nexus.covers1624.net/repository/maven-hosted/

ChickenChunks, CodeChickenCore, CodeChickenLib, EnderStorage, ForgeMultipart, NotEnoughItems, Translocators, WR-CBE
https://maven.falsepattern.com/releases LightningOverhaul, AnimFix, CrashGuard, DyamicRendering, EndlessIDs, FalsePatternLib, JarLoader, LagGoggles, SSMLegacy, Triangulator, ...
https://maven.ic2.player.to/ IndustrialCraft, Forestry, ...
https://maven.k-4u.nl/ Boilerplate, InGameWiki, K4Lib, MoarCarts, PneumaticCraft, ServerInfoProvider, Steamcraft2, ...
https://maven.latmod.com/
https://maven.mcmoddev.com

Backup: https://maven.tophatcat.dev/

Baubles, LLibrary, Thaumcraft, VeinMiner, ...
https://maven.minecraftforge.net/

Backup: https://repo.spongepowered.org/repository/forge-proxy/

Biomes O' Plenty, HelpFixer, MalisisCore, MalisisDoors, Mixin, IronChest, ...
https://maven.modmuss50.me/
https://maven.mjrlegends.com/ ExtraPlanets, ...
https://ci.tterrag.com/

https://maven.tterrag.com

Chisel, CTMLib, CustomThings, DifficultyRecipes, EnderIO, EnderCore, EnderZoo, Ex-Astris, Ex-Nihilo, RecipeTweakingCore, SuperMassiveTech, ttCore, ...
http://mc.lunatri.us/files/ Config Patcher, DynIMC, Extension Fixer, InGame Info XML, InGame Mod Configs, Laser, Level, LunatriusCore, Monster Spawner Highlighter, Profiles, Schematica, SchematicaPlugin, Stackie, Tracer
https://minecraft.curseforge.com/api/maven/ Any CurseForge file
http://minetweaker3.powerofbytes.com/download/ MineTweaker3
https://mobiusstrip.eu/maven AdminCommandsToolbox, JABBA, MobiusCore, Netty-Opis, Opis, WAILA, ...
https://modmaven.dev/ AccountSync, AddictedToRed, AI Improvements, Announcement Mod, Armory, Armory Gem Items, AssemblyLine, Atomic Science, Bagable Plants, Basic Industry, boilerplate, BoneTorch, cardboardboxes, ChickenChunks, CodeChickenCore, CodeChickenLib, Colored Chests, Colored Pots, Come Closer, Controlling, Corruption, Ender Storage, Forge Multipart, GasCan, GrapplingHook, HelmBucket, ICBM, ICBM Classic, ICBM Classic Sentry, IguanaTinkerTweaks, IguanaTweaks, Magic Mirror, MC Profiler, MFFS, MilitaryBaseDecour, MinecraftJUnit, moarcarts, NotEnoughItems, NVFix, ProgressWorldCleanup, RedCow, Sentry AA, SkyIslandGenerator, steamcraft2, Translocator, VE Fluid Handling, Voltz Engine, Voltz Engine Essentials, Wooden Bucket, Wooden Rails, Wooden Shears, WR-CBE, ...
https://mvn.falsepattern.com/releases GasStation, LightingOverhaul, MixinExtras, AnimFix, CartLoad, CrashGuard, DynamicRendering, EndlessIDs, FalsePatternLib, FalseTweaks, JarLoader, LagGogglesLegacy, SSMLegacy, Triangulator, GalactiCraft-Core, GalactiCraft-Planets, MicdoodleCore, Biome Wand, Space Core, CoroUtil, EnhancedBiomes, Tropicraft, ...
https://purpleposeidon.github.io/fz_archive/ Factorization
https://repo.spongepowered.org/maven/ Mixin, ...
https://www.cursemaven.com Any CurseForge file
https://www.mod-buildcraft.com/releases/BuildCraft/ Buildcraft, BuildCraft Compat
https://www.ryanliptak.com/maven/ AppleCore

Resources

Not every wiki/tutorial/article/... listed here contains information about Minecraft version 1.7.10 but some topics haven't changed much and often the general methodology is the same. The newer the version, the less comparable the inner workings of Minecraft/Forge are to 1.7.10.

Use Ctrl+F if you look for something specific.

You can look at the source-code of most mods included in GTNH here.

Link Collections

Name Version(s)
MMD Resource Index Various
Minecraft Modding Overview (WIP) Resources for Mr. Turner‎ (Archive) 1.6, 1.7
Awesome Minecraft 1.7.10 1.7.10

Tutorials / Blogs

Name Version(s) Topics (including, but often not limited to)
MMD Modding-Resources Various Blocks, Commands, Entities, Fluids, Items, Rendering, ...
Jabelar's Minecraft Forge Modding Tutorials Various Getting Started, Concepts, Registries, Entities, Blocks, Items, Armor, Weapons, Tools, Fluids, Tanks, Recipes, Ore Dictionary, Loot, Tile Entities, Networking, Events, Models, Animations, Rendering, Assets, Enchantments, GUIs, Keybindings & Mouse, Achievements / Advancements, Configs, World Generation, Creative Tabs, Particles, Sounds, Commands, IMC / Compat, ...
#knowledgebase (Minecraft Pack Development Discord) Various Various bits of information on Mod(pack) Development
#resources (Blockbench Discord) All Modeling, Textures, Animation
2xsaiko's Mixin Cheatsheet All Cheatsheet for mixins
TelepathicGrunt' How to Mixin All Mixins
Mapping and Modding Tutorials on Minecraft Forum All? Various Topics
Old Forge Wiki Tutorials (Archive) 1.3 - 1.7 Gettings Started, Concepts, Blocks, Items, Recipes, Events, Ore Generation, Tile Entities, Commands, Rendering, Configs, Models, Biome Dictionary, Ore Dictionary, Achievements, Sounds, GUIs, Networking, NBT, Containers, Entities, Multiblocks, Fluids, Scala, ...
Wuppy's Tutorials (Archive) 1.3 - 1.8 Gettings Started, Recipes, Loot, Assets, Blocks, Items, Tools, Rendering, World Generation, Crops, Entities, Dimensions, ...
Vswe's Summer Courses (Archive) 1.6.2 Java Basics, Getting Started, Items, Blocks, Tile Entities, Entities, World Gen, Sounds, Particles, Models, Textures, Animations
The Grey Ghost's Minecraft By Example [Blog|GitHub] 1.6 - 1.16 Concepts, Blocks, Items, Rendering, User Input, Packets, Entities, GUIs, Containers, Tools, Redstone, ...
EMX Tutorials 1.7 Getting Started, Items, Blocks, Recipes, Keybindings, Textures, Drops, GUIs, NBT, Models, Containers, ...
coolAlias' Forge Tutorials 1.7 Armor, Villager Trades, Inventories, Events, Rendering, ...
Using the Simple Network Implementation (SimpleNetworkWrapper) [Tutorial (Archive)|Example] 1.7 Networking
Vike's ASM Tutorial [Part 1|Part 2] 1.7 ASM
Bedrock Miner's Tutorials (Archive) 1.7, 1.8 Getting started, Concepts, Blocks, Items, Tools, Armor, Food, Recipes, ...
TheXFactor117's Forge Modding Tutorials 1.7, 1.8 Getting Started, Items, Blocks, Armor, Tools, Ore Generation, NBT, Tile Entities, Assets, Creative Tabs, Recipes, Entities, ...
Darkhax' Tutorials 1.8 - 1.12 Custom Entity Data, Loot Tables, Events, Structure Generation, Update Checker, IMC, Jar Signing, Access Transformers, Rendering, CraftTweaker Support, Mixin
McJty's Tutorials 1.9+ Getting Started, Concepts, Configs, Blocks, Items, Tile Entities, Recipes, GUIs, Inventories, Entities, Rendering, Networking, Commands, Dimensions, WAILA Integration, ...
ShadowFacts' Tutorials 1.10 - 1.12 Getting Started, Concepts, Items, Models, Blocks, Blockstates, Assets, Crops, Creative Tabs, Recipes, Ore Dictionary, Food, Tools, Armor, World Generation, Tile Entities, Inventories, GUIs, Rendering, ...
suppergerrie2's Tutorials 1.12 - 1.15 Getting Started, Items, Blocks, Recipes, Ore Generation, Food, Creative Tabs, Tools, Slabs, Enchantments, Crops, Block States, Events, ...
Cubic Interpolation - Helpful Things for Making Mods with Forge for Minecraft 1.15 1.15 Events, Registries, Tile Entities, Dimensions, Loot, Data Generators, Configs, NBT, ...
Forge Community Wiki LTS, Latest Getting Started, Concepts, Blocks, Items, Tile Entities, Events, Resources, Data, Models, Networking, Potions, Particles, Sound, Events, Loot, Key Bindings, Access Transformers, ...
Java Docs Tutorials Not Minecraft specific Java
Red Blob Games Not Minecraft specific Path Finding, Graph Theory, Map Generation, Procedural Generation
0 FPS Not Minecraft specific Collision Detection, Geometry, Mathematics, Voxels, Shape Modeling, Ambient Occlusion, ...
Java introduction to MethodHandles - a faster reflection API replacement Not Minecraft specific Java, Reflection

Wikis / Docs

Name Topics
CraftTweaker Docs CraftTweaker
Gradle User Manual Gradle
Minecraft Forge Event List Vanilla and Forge Events (MC 1.12+)
Fabric Wiki - Introduction to Mixins Mixins
FTB Wiki Unofficial Information on many Mods
Git Docs Git
Data Driven Shaders by Ladysnake MC 1.7+ Post Process Shaders
Mixin Extras Wiki Mixin Extras
Mixin Wiki Mixins
Official Forge Docs [Latest|Legacy] Forge
Legacy Modding Wiki Wiki for Modding on older Minecraft Versions (WIP)
3 Wiki (Archive) MineTweaker 3
DocsMC (1.7.10), MCJavaDocs (1.7.10), ForgeJavaDocs (1.7.10 - 1.12.2), ForgeJavaDocs-NG (1.12.2) Javadocs for Minecraft, FML and Minecraft Forge
VisualVM Docs VisualVM
wiki.vg Protocols, Authentification, NBT, etc.
Wikipedia More than you can think of (but not everything)

Raven's list of rendering resources

OpenGL resources:

  • [1] - a good C++ tutorial for opengl
  • [2] - another step-by-step opengl c++ tutorial
  • [3] - lwjgl3 tutorial book about 3d gamedev with code samples
  • [4] - a short, but useful tutorial into modern opengl's rendering pipeline
  • [5] - a lot of useful diagrams and linear algebra for 3d rendering with opengl
  • [6] - a lot of example LWJGL3 programs showing off implementations of various rendering techniques, it's a small gold mine

Reference docs:

  • [7] - nice site to search&view khronos's official docs
  • [8] - a cheat sheet you can print out with the full opengl API

More advanced stuff:

  • [9] - Raytracing in a Weekend series, teaches you a lot about computer graphics (beware, raytracing != rasterization which is what opengl uses, but most of the math still applies)
  • [10] - a blogpost on 1 efficient method of batching drawcalls for performance
  • [11] a great blog from an AMD gpu driver developer, lots of valuable info here

Search for GDC, AMD, NVIDIA and AMD talks on youtube about rendering topics too Super advanced stuff:

  • [12] - a series of blogposts going really deep into how GPUs work
  • [13] - the full instruction set architecture doc for AMD GCN3 GPUs, useful to understand what kind of machine code GPUs actually execute

Random non-rendering stuff: https://gameprogrammingpatterns.com/contents.html - a book (available for free online) about common patterns in game code

Help

Maven Local Repository

Sometimes you want to make cross-mod changes. In order to make use of code changed locally from another mod, use maven local.

  • Run publishToMavenLocal for your dependency mod. Setting environment variable VERSION allows you to publish it with specified tag, like 99.99.99
  • Add mavenLocal() to your repositories.gradle in your dependent mod, and change dependencies.gradle to your desired version.
Environment variable can be set on IDEA GUI

Note that this doesn't work on GitHub, so in order to pass CI, you need to publish pre tag online. If you're not in the GTNH team, ask others to publish it.

Hotswap

Hotswap allows you to reflect code changes without relaunching the game. Use 1b. Run Client (Java 17, Hotswap) or 2b. Run Server (Java 17, Hotswap) to launch the game, and use Run > Debugging Actions > Reload Changed Classes to hotswap.

Dependency types

The following table shows if a source dependency - later called the Source - you included in Your Mod is visible to Your Mod and the mods that depend on Your Mod. For instance, implementation makes the Source visible to Your Mod at compile and runtime, but only at runtime to the Dependent mods, meaning that the Dependent mods are not able to use a class from Your Mod if it implements an interface from the Source. There are also test versions of some, you probably just want testImplementation.

Your mod Dependent mod
compile runtime compile runtime
api Yes Yes Yes Yes
implementation Yes Yes No Yes
compileOnly Yes No No No
compileOnlyApi Yes No Yes No
runtimeOnlyNonPublishable No Yes No No
devOnlyNonPublishable Yes Yes No No
runtimeOnly No Yes No Yes
compile Deprecated. Use api or implementation

You can also read document on ExampleMod repository for details.

JVM flags

These are some useful JVM flags for development purposes. A full, detailed list can be found in the table below.

  • -Dmixin.debug=true Enable Mixin Debug
  • -Dmixin.debug.verbose=true Verbose Debug Messages
  • -Dmixin.debug.export=true Export classes after mixins have been applied. If you include fernflower in your classpath, or copy org.jetbrains.fernflower into your mixin jar the exported classes will be decompiled
  • -Dmixin.debug.countInjections=true Throw an error if the injection count doesn't match expectations
  • -Dlegacy.debugClassLoading=true Class Load Debugging
  • -Dlegacy.debugClassLoading=true -Dlegacy.debugClassLoadingFiner=true -Dlegacy.debugClassLoadingSave=true Dump classes to ./CLASSLOADER_TEMP
  • -Dfml.debugAccessTransformer=true Enable debug logging of access transformers
Flag Default Result Code Reference
-Dfml.badPacketCounter 100 Sets the number of leaked packets before a warning is logged. FMLProxyPacket
-Dfml.coreMods.load Allows setting a comma separated list of coremod classes to load before "normal" coremods are discovered. CoreModManager
-Dfml.debugAccessTransformer false true: Logs detailed debug information when applying Access Transformers. AccessTransformer
-Dfml.debugAPITransformer false true: Logs detailed debug information when processing @Optional annotations. ModAPITransformer
-Dfml.debugExit false true: Logs the stacktrace before exiting the java application. FMLCommonHandler
-Dfml.debugClassPatchManager false true: Logs detailed debug information when appling runtime patches. ClassPatchManager
-Dfml.debugRegistryEntries false true: Logs detailed debug information about the block and item registries. FMLControlledNamespacedRegistry
-Dfml.doNotBackup false true: Prevents the creation of a backup when loading an old or damaged save. GuiOldSaveLoadConfirm
-Dfml.dumpPatchedClasses false true: Writes classes to a temp directory after runtime patching. The file locations are logged. ClassPatchManager
-Dfml.dumpRegistry false true: Dumps the item registry to ./itemStackRegistry.csv after the mods have finished loading. GameData
-Dfml.ignoreInvalidMinecraftCertificates false true: Continues loading the game even if an invalid Minecraft certificate was detected. FMLSanityChecker
-Dfml.ignorePatchDiscrepancies false true: Continues loading the game even if discrepancies have been detected while applying runtime patches. ClassPatchManager
-Dfml.LogContext false true: Adds a mod's name to the Log4J thread context (key: mod) before invoking the mod's event handler. The name is removed from the context afterwards. ASMEventHandler
-Dfml.loginTimeout 600 Sets the time (in ticks) before a login attempt times out. FMLNetworkHandler
-Dfml.modStates Allows setting mod states by providing a (semi-)colon separated list of =-separated key/value-pairs. The value is a boolean representing the "enabled" state when "true". Example:

-Dfml.modStates=IC2=true;Railcraft=false This can also be done via a fmlModState.properties file, located in the config directory.

Loader
-Dfml.noGrab false true: Prevents the mouse cursor from being grabbed when focussing the game. MouseHelper
-Dfml.queryResult Uses confirm/cancel to answer any queries during the load process. StartupQuery
-Dfml.readTimeout 30 Sets the time (in seconds) before a read times out. FMLNetworkHandler
-Dfml.remappingDebug false Condition for -Dfml.remappingDebug.dumpFieldMaps and -Dfml.remappingDebug.dumpMethodMaps. FMLDeobfuscatingRemapper
-Dfml.remappingDebug.dumpFieldMaps false true: Logs all field mappings of a class when that class is loaded. FMLDeobfuscatingRemapper
-Dfml.remappingDebug.dumpMethodMaps false true: Logs all method mappings of a class when that class is loaded. FMLDeobfuscatingRemapper
-Dfml.skipFirstTextureLoad true true: Skips the first loading of textures. TextureMap
-Dfmlbuild.build.number missing FMLInjectionData
-Dfmlbuild.deobfuscation.hash deadbeef Unused FMLInjectionData
-Dfmlbuild.major.number missing FMLInjectionData
-Dfmlbuild.mcpversion missing FMLInjectionData
-Dfmlbuild.mcversion missing FMLInjectionData
-Dfmlbuild.minor.number missing FMLInjectionData
-Dfmlbuild.revision.number missing FMLInjectionData
-Dforge.debugBlockEvent false true: Logs when (Multi)PlaceEvents are fired. BlockEvent
-Dforge.debugBlockSnapshot false true: Logs creations/restorations of block snapshots. BlockSnapshot
-Dforge.forceDisplayStencil false true: Initializes the LWJGL Display with 8 stencil bits.

false: Initializes the LWJGL Display with 0 stencil bits.

ForgeHooksClient
-Dlegacy.debugClassLoading false Condition for the following three flags. true: Logs additional debug information when loading/transforming classes. LaunchClassLoader
-Dlegacy.debugClassLoadingFiner false true: Logs additional debug information while class transformers run. LaunchClassLoader
-Dlegacy.debugClassLoadingSave false true: Saves a copy of every class before and after each class transformer runs to the ./CLASSLOADER_TEMP directory. LaunchClassLoader
-Dlegacy.debugClassLoadingSlim false true: Disables -Dlegacy.debugClassLoadingSave. LaunchClassLoader
-Dmixin.checks false true: Enables all checks. MixinEnvironment$Option
-Dmixin.checks.interfaces false true: Checks that all declared interface methods are implemented on a class after mixin application. Requires -Dmixin.checks=true. MixinEnvironment$Option
-Dmixin.checks.interfaces.strict true If interface check is enabled, "strict mode" applies the implementation check even to abstract target classes. Setting this option to false causes abstract targets to be skipped when generating the implementation report. MixinEnvironment$Option
-Dmixin.debug false true: Enables all mixin debugging options. MixinEnvironment$Option
-Dmixin.debug.countInjections false true: Elevates failed injections to an error condition, see Inject#expect for details. Requires -Dmixin.debug=true. MixinEnvironment$Option
-Dmixin.debug.export false true: Enables post-mixin class export. This causes all classes to be written to the ./.mixin.out directory within the runtime directory after mixins are applied, for debugging purposes. Requires -Dmixin.debug=true. MixinEnvironment$Option
-Dmixin.debug.export.decompile true true: Allows fernflower to be disabled even if it is found on the classpath. Requires -Dmixin.debug.export=true. MixinEnvironment$Option
-Dmixin.debug.export.decompile.async true true: Runs fernflower in a separate thread. In general this will allow export to impact startup time much less (decompiling normally adds about 20% to load times) with the trade-off that crashes may lead to undecompiled exports. Requires -Dmixin.debug.export.decompile=true. MixinEnvironment$Option
-Dmixin.debug.export.decompile.mergeGenericSignatures true By default, if the runtime export decompiler is active, mixin generic signatures are merged into target classes. However this can cause problems with some runtime subsystems which attempt to reify generics using the signature data. Set this option to false to disable generic signature merging. Requires -Dmixin.debug.export.decompile=true. MixinEnvironment$Option
-Dmixin.debug.export.filter Export filter, if omitted allows all transformed classes to be exported. If specified, acts as a filter for class names to exportand only matching classes will be exported. This is useful when using Fernflower as exporting can be otherwise very slow. The followingwildcards are allowed:
  • * Matches one or more characters except dot (.)
  • ** Matches any number of characters
  • ? Matches exactly one character

Requires -Dmixin.debug.export=true.

MixinEnvironment$Option
-Dmixin.debug.profiler true true: Enable the performance profiler for all mixin operations (normally it is only enabled during mixin prepare operations). MixinEnvironment$Option
-Dmixin.debug.strict false true: Enables strict checks. Requires -Dmixin.debug=true. MixinEnvironment$Option
-Dmixin.debug.strict.targets false true: Enables strict checking for mixin targets. Requires -Dmixin.debug.strict=true. MixinEnvironment$Option
-Dmixin.debug.strict.unique false If false, Unique public methods merely raise a warning when encountered and are not merged into the target. If true, an exception is thrown instead. Requires -Dmixin.debug.strict=true. MixinEnvironment$Option
-Dmixin.debug.verbose false true: Enables verbose mixin logging (elevates all DEBUG level messages to INFO level). Requires -Dmixin.debug.export=true. MixinEnvironment$Option
-Dmixin.debug.verify false true: Runs the CheckClassAdapter on all classes after mixins are applied, also enables stricter checks on mixins for use at dev-time, promotes some warning-level messages to exceptions. Requires -Dmixin.debug.export=true. MixinEnvironment$Option
-Dmixin.dumpTargetOnFailure false true: Dumps the bytecode for the target class to disk when mixin application fails. MixinEnvironment$Option
-Dmixin.env.allowPermissiveMatch true When mixin.env.remapRefMap is enabled and a refmap is available for a mixin config, certain injection points are allowed to fail over to a "permissive" match which ignores the member descriptor in the refmap. To disable this behaviour, set this property to false. MixinEnvironment$Option
-Dmixin.env.compatLevel Default compatibility level to operate at. MixinEnvironment$Option
-Dmixin.env.disableRefMap false true: Disables refmap when required. MixinEnvironment$Option
-Dmixin.env.ignoreRequired false true: Globally ignores the "required" attribute of all configurations. MixinEnvironment$Option
-Dmixin.env.refMapRemappingEnv searge When using mixin.env.refMapRemappingFile, this setting overrides the default source environment. However note that the specified environment type must exist in the orignal refmap. MixinEnvironment$Option
-Dmixin.env.refMapRemappingFile If mixin.env.remapRefMap is enabled, this setting can be used to override the name of the SRG file to read mappings from. The mappings must have a source type of searge and a target type matching the current development environment. If the source type is not searge then the mixin.env.refMapRemappingEnv should be set to the correct source environment type. MixinEnvironment$Option
-Dmixin.env.remapRefMap false true: Rather than disabling the refMap, you may wish to remap existing refMaps at runtime. This can be achieved by setting this property and supplying values for mixin.env.refMapRemappingFile and mixin.env.refMapRemappingEnv. Though those properties can be ignored if starting via GradleStart (this property is also automatically enabled if loading via GradleStart). MixinEnvironment$Option
-Dmixin.env.shiftByViolation warn Behaviour when the maximum defined At#by value is exceeded in a mixin. Currently the behaviour is to warn. In later versions of Mixin this may be promoted to error.

Available values for this option are:

  • ignore Pre-0.7 behaviour, no action is taken when a violation is encountered.
  • warn Current behaviour, a WARN-level message is raised for violations.
  • error Violations throw an exception.
MixinEnvironment$Option
-Dmixin.hotSwap false true: Enables the hot-swap agent. MixinEnvironment$Option
-Dmixin.ignoreConstraints false true: Ignores all constraints on mixin annotations, outputs warnings instead. MixinEnvironment$Option
-Dmixin.initialiserInjectionMode default Behaviour for initialiser injections, current supported options are "default" and "safe". MixinEnvironment$Option

Remote debugging

  • -agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=5005 to wait for a debugger to be attached to the game before running code, put this in launcher args to debug the full pack
  • In IntelliJ, use Run->Attach to process to attach the debugger to the running instance.