lillero-loader/README.md

lillero-loader

don't do coremods

A simple LaunchPlugin loading bare ASM patches into our beloved block game.

Why

Until minecraft 1.12, modifying minecraft game code wasn't too esoteric: it was necessary to register as "CoreMod", but Forge would then load your mod when minecraft itself was loading, allowing to lookup classes and patch them. Since 1.13+ net.minecraft.launchwrapper.Launch and net.minecraftforge.fml.relauncher.IFMLLoadingPlugin are no longer available, replaced by cpw's modlauncher. This makes a new approach necessary.

How

Modlauncher loads some Java services at startup (using builtin ServiceLoader mechanism), allowing to load arbitrary classes and modules when launching Minecraft. More specifically, the ILaunchPluginService is loaded before game classes are put in memory, and is passed all game classes for patching. This allows us to create a custom Launch Plugin (this project) that will load and apply arbitrary patches at start time. Patches must be defined themselves as services inside each mod, implementing IInjector (from lll) They must define in which class they will patch, and which method, and then implement an inject() method which will be called with the correct Method Node. Note that, as of now, Searge names must be used for methods and fields.

I know what I'm doing, spill your beans

Basically, our ILaunchPluginService implements 3 methods which are called in 3 phases:

• addResources() : will be called first for each external mod that was found, providing an absolute path to the jar. Our LaunchPlugin will try to load IInjector services from each of these resources, saving them for later.
• handlesClass() : will be called for each game class modlauncher discovered. Our LaunchPlugin will signal that it wants to change classes for which an IInjector was registered.
• processClassWithFlags() : will be called for each game class which was signaled before, allowing to apply modifications to it.

Technically, handlesClass() and processClassWithFlags() are called concurrently, but assuming they don't make the explanation easier.