Mixin is a trait/mixin framework for Java using ASM and hooking into the runtime classloading process via a set of pluggable built-in or user-provided services. Built-in services currently support Mojang's LegacyLauncher system, though this is deprecated in favour of ModLauncher by cpw, which has greater extensibility and has support for Java 8 and later.

The main documentation for Mixin can be found in the Wiki.

Additional documentation for individual features and annotations can be found in the extensive Javadoc. For additional help use the channel #mixin on the Sponge Discord Server.

Mixin binaries are available via Jenkins and are published to the following maven repositories:

• https://repo.spongepowered.org/repository/maven-public/ - SNAPHOTs and RELEASE builds
• https://files.minecraftforge.net/maven/ - RELEASE builds only

For handling obfuscation tasks, Mixin provides an Annotation Processor which works at compile time to generate obfuscation mappings for your toolchain to apply. If using Gradle 5 or later, annotation processors are no longer automatically loaded from compile configurations and must be specified explicitly via annotationProcessor configurations. For this purpose, Mixin provides "fat jar" artefacts containing all required dependencies via the :processor classifier. For example if your build uses the dependency org.spongepowered:mixin:1.2.3 then your annotationProcessor configuration should specify dependency org.spongepowered:mixin:1.2.3:processor.

If you are using Mixin in a Minecraft Forge project then the MixinGradle plugin can be used to simplify the configuration of the Mixin Annotation Processor. It provides a simple syntax for configuring the Mixin AP for your project, see the MixinGradle README for how to configure MixinGradle.

When developing using Mixin, you can use the Mixin Annotation Processor within Eclipse to provide context-sensitive errors and warnings to help you more easily troubleshoot your mixins. To do so:

1. Run the gradle build command to generate the mixin jar
2. Open the properties of your eclipse project and navigate to Java Compiler -> Annotation Processing -> Factory Path
3. Check the Enable project specific settings checkbox
4. Click the Add External JARs button and select the generated mixin jar with the suffix -processor (hint: it should be in Mixin/build/libs)
5. Navigate up one level to Java Compiler -> Annotation Processing
6. Check the Enable project specific settings checkbox
7. Check the Enable annotation processing checkbox
8. Click the New... button next to the Processor options box

• Set Key to reobfSrgFile
• Set Value to the fully-qualified path to the mcp-srg.srg file (the location of the mapping file varies by platform, if you are unsure where to find it please follow the discord link below).

9. Click OK to apply the changes

Enhanced functionality for working with Mixin in IntelliJ IDEA is available via the Minecraft Development for IntelliJ IDEA plugin developed by DemonWav.

Specifying the minVersion property in your configurations is extrememly important. The following version history can be used to determine when features were introduced (and sometimes when major bugs are squashed) in order to help you determine which minVersion you should specify.