Funny mixin example

build.gradle

@@ -1,15 +1,22 @@
 buildscript {
     repositories {
         maven { url = 'https://maven.minecraftforge.net' }
+        maven { url = "https://repo.spongepowered.org/repository/maven-public/" }
         mavenCentral()
     }
     dependencies {
         classpath group: 'net.minecraftforge.gradle', name: 'ForgeGradle', version: '4.1.+', changing: true
+        classpath group: "org.spongepowered", name: "mixingradle", version: "0.7-SNAPSHOT"
     }
 }
 apply plugin: 'net.minecraftforge.gradle'
 apply plugin: 'eclipse'
 apply plugin: 'maven-publish'
+apply plugin: "org.spongepowered.mixin"
+
+mixin {
+    add sourceSets.main, "specialmobs.mixins.refmap.json"
+}
 
 // The mod's version and id
 version = "${mc_version}-${mod_version}"
@@ -30,6 +37,11 @@ minecraft {
             property 'forge.logging.markers', 'REGISTRIES'
             property 'forge.logging.console.level', 'debug'
 
+            property "mixin.debug.export", "true"
+            property 'mixin.env.disableRefMap', 'true'
+
+            arg "-mixin.config=specialmobs.mixins.json"
+
             mods {
                 deadlyworld {
                     source sourceSets.main
@@ -43,6 +55,11 @@ minecraft {
             property 'forge.logging.markers', 'REGISTRIES'
             property 'forge.logging.console.level', 'debug'
 
+            property "mixin.debug.export", "true"
+            property 'mixin.env.disableRefMap', 'true'
+
+            arg "-mixin.config=specialmobs.mixins.json"
+
             mods {
                 deadlyworld {
                     source sourceSets.main
@@ -88,6 +105,23 @@ dependencies {
     // Add in JEI and TOP to assist debugging during development
     runtimeOnly fg.deobf("mezz.jei:jei-${mc_version}:${jei_version}")
     runtimeOnly fg.deobf("mcjty.theoneprobe:TheOneProbe-${top_version}")
+
+    annotationProcessor 'org.spongepowered:mixin:0.8.2:processor'
+}
+
+jar {
+    manifest {
+        attributes([
+                "Specification-Title": "Special Mobs",
+                "Specification-Vendor": "FatherToast",
+                "Specification-Version": "1", // We are version 1 of ourselves
+                "Implementation-Title": project.name,
+                "Implementation-Version": "${version}",
+                "Implementation-Vendor" :"FatherToast",
+                "Implementation-Timestamp": new Date().format("yyyy-MM-dd'T'HH:mm:ssZ"),
+                "MixinConfigs": "specialmobs.mixins.json"
+        ])
+    }
 }
 
 jar.finalizedBy('reobfJar')

src/main/java/fathertoast/specialmobs/common/mixin/EntityRendererManagerMixin.java

@@ -0,0 +1,69 @@
+package fathertoast.specialmobs.common.mixin;
+
+import com.mojang.blaze3d.matrix.MatrixStack;
+import net.minecraft.client.GameSettings;
+import net.minecraft.client.gui.FontRenderer;
+import net.minecraft.client.renderer.IRenderTypeBuffer;
+import net.minecraft.client.renderer.entity.EntityRendererManager;
+import net.minecraft.client.renderer.entity.ItemRenderer;
+import net.minecraft.client.renderer.texture.TextureManager;
+import net.minecraft.entity.Entity;
+import net.minecraft.resources.IReloadableResourceManager;
+import net.minecraft.world.IWorldReader;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Redirect;
+
+/**
+ * This is our EntityRendererManager mixin!
+ *
+ * All mixin classes must be annotated with @Mixin(TargetClass)
+ *
+ * Also note that all mixin classes must exist in their own dedicated mixin package. Having a non-mixin class
+ * inside the package you have specified to be your mixin package will not go well.
+ *
+ * Its a good rule of thumb to make your mixin classes abstract, as they should never be instantiated.
+ *
+ * This mixin example is not fantastic as it only scratches the surface of the worm can that is mixin,
+ * but I figured it at least had some relevance since shadow render canceling was a topic earlier.
+ *
+ * NOTE: All mixins must be registered in the mod's mixin config.
+ *       the mixin config can be found inside the mod's resources folder: "specialmobs.mixins.json".
+ *       When you remove this mixin from the config, it will no longer be active.
+ */
+@Mixin(EntityRendererManager.class)
+public abstract class EntityRendererManagerMixin {
+
+    /**
+     *  Constructor matching target class constructor. Not required in this case, but generally nice to have
+     */
+    public EntityRendererManagerMixin(TextureManager textureManager, ItemRenderer p_i226034_2_, IReloadableResourceManager resourceManager, FontRenderer fontRenderer, GameSettings gameSettings) {
+
+    }
+
+    /**
+     * Simple redirect injection.
+     *
+     * Here we use the @Redirect annotation on a target method in our mixin target class.
+     * This annotation lets us swap out invocations in the target method with our own.
+     *
+     * The first parameter of annotation is the target method name; the method we will be messing around with
+     * The second parameter is the "at" (where in the target method should we look for invocations to swap?)
+     *
+     * There are various ways to determine where we want to do things, but in this specific example,
+     * we want to cancel every call to "renderShadow" in the target method.
+     *
+     * value = "INVOKE" - This specifies that we should only look for INVOKE opcodes
+     * target = "Lnet/minecraft/client..blah..blah" - This is the full name of the member we want to redirect, in this case "renderShadow"
+     *
+     * As you can see, our injection method has an empty body. This is because we wish to do absolutely nothing instead of rendering entity shadows.
+     *
+     * NOTE: It is required that our injected method has the same parameters as our target, as shown below.
+     *       the "name" of our injection method does not matter. It can be anything, but its not a bad idea to
+     *       name it something intuitive.
+     */
+    @Redirect(method = "render", at = @At(value = "INVOKE", target = "Lnet/minecraft/client/renderer/entity/EntityRendererManager;renderShadow(Lcom/mojang/blaze3d/matrix/MatrixStack;Lnet/minecraft/client/renderer/IRenderTypeBuffer;Lnet/minecraft/entity/Entity;FFLnet/minecraft/world/IWorldReader;F)V"))
+    public void onRender(MatrixStack matrixStack, IRenderTypeBuffer buffer, Entity entity, float p_229096_3_, float p_229096_4_, IWorldReader worldReader, float p_229096_6_) {
+
+    }
+}

src/main/resources/specialmobs.mixins.json

@@ -0,0 +1,19 @@
+{
+  "required": true,
+  "package": "fathertoast.specialmobs.common.mixin",
+  "compatibilityLevel": "JAVA_8",
+  "minVersion": "0.8",
+  "refmap": "specialmobs.mixins.refmap.json",
+
+  "mixins": [],
+
+  "client": [
+    "EntityRendererManagerMixin"
+  ],
+
+  "server": [],
+
+  "injectors": {
+    "defaultRequire": 1
+  }
+}