Use a shadowC configuration, make an info window instead of an "installer", and include fabric-resource-loader-v0.

build.gradle.kts

@@ -1,3 +1,4 @@
+import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar
 plugins {
     kotlin("jvm") version "1.5.0-M2"
     id("com.github.johnrengelman.shadow") version "6.1.0" apply false
@@ -14,10 +15,13 @@ architectury {
 }
 
 subprojects {
+    val shadowC by configurations.creating
+    tasks.withType(ShadowJar::class) { this.configurations = listOf(shadowC) }
     apply(plugin = "org.jetbrains.kotlin.jvm")
     apply(plugin = "forgified-fabric-loom")
     apply(plugin = "com.github.johnrengelman.shadow")
     dependencies {
+        shadowC(kotlin("stdlib-jdk8"))
         "minecraft"("com.mojang:minecraft:${rootProject.property("minecraft")}")
     }
 }
@@ -30,13 +34,14 @@ allprojects {
         sourceCompatibility = JavaVersion.VERSION_1_8
     }
     tasks {
-        withType(com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar::class) {
+        jar.get().isEnabled = false
+        withType(ShadowJar::class) {
             relocate("kotlin", "${rootProject.group}.kotlin")
-            relocate("${rootProject.group}.${rootProject.name.toLowerCase()}", "${rootProject.group}.${rootProject.name.toLowerCase()}.${this@allprojects.name}")
+            archiveClassifier.set("shadow")
         }
         withType(Jar::class) {
-            manifest.attributes["Main-Class"] = "$groupAndName.exec.InstallerKt"
-            from("$rootDir/LICENSE")
+            manifest.attributes["Main-Class"] = "$groupAndName.exec.InfoKt"
+            from("$rootDir/LICENSE.txt")
             archiveBaseName.set("${rootProject.name}-${rootProject.version}")
         }
         withType(org.jetbrains.kotlin.gradle.tasks.KotlinCompile::class) {
@@ -57,7 +62,12 @@ allprojects {
             }
         }
         withType(net.fabricmc.loom.task.RemapJarTask::class) {
-            if (!archiveBaseName.get().startsWith("common")) destinationDirectory.set(file("$rootDir/remappedJars"))
+            val shadowTask = getByName("shadowJar") as ShadowJar
+            dependsOn(shadowTask)
+            archiveBaseName.set(shadowTask.archiveBaseName)
+            if (!archiveBaseName.get().contains("common")) destinationDirectory.set(file("$rootDir/remappedJars"))
+            input.set(shadowTask.archiveFile)
+            archiveClassifier.set(this@allprojects.name)
         }
         withType(ProcessResources::class) {
             val modVersionPair: Pair<String, String> = "mod_version" to (rootProject.version as String)

common/src/main/java/fr/username404/snowygui/exec/info.kt

@@ -0,0 +1,53 @@
+package fr.username404.snowygui.exec
+
+import java.awt.*
+import javax.swing.JFrame
+import javax.swing.JPanel
+
+private val Background: Color = Color(
+    32, // Red
+    32, // Green
+    135, // Blue
+    120
+)
+
+object ExecObj {
+    fun createWindow() {
+        val frame = JFrame("Hey!")
+        with(frame) {
+            createInterface(this)
+        }
+    }
+    private fun createInterface(frame: JFrame) {
+        frame.setLocationRelativeTo(null)
+        val panel: JPanel = object: JPanel() {
+            override fun paintComponent(g: Graphics?) {
+                if (g is Graphics2D) {
+                    val p: Paint = GradientPaint(
+                        0.0f,
+                        0.0f,
+                        Background,
+                        width.toFloat(),
+                        height.toFloat(),
+                        Color(
+                            52,
+                            170,
+                            166,
+                            255
+                        ),
+                        true
+                    )
+                    val g2d = g
+                    g2d.paint = p
+                    g2d.fillRect(0, 0, width, height)
+                } else {
+                    super.paintComponent(g)
+                }
+            }
+        }
+    }
+}
+
+fun main() {
+    ExecObj.createWindow()
+}

common/src/main/java/fr/username404/snowygui/exec/installer.kt

@@ -1,2 +0,0 @@
-package fr.username404.snowygui.exec
-

fabric/build.gradle.kts

@@ -16,11 +16,12 @@ dependencies {
     mappings(loom.officialMojangMappings())
     modApi("${Groups.Fabric}:fabric-loader:${rootProject.property("fabric_loader_version")}")
     modApi("${Groups.FabricApi}:fabric-resource-loader-v0:${rootProject.property("fabric_resource_loader_version")}")
+    include("${Groups.FabricApi}:fabric-resource-loader-v0:${rootProject.property("fabric_resource_loader_version")}") { isTransitive = false }
     modRuntime(modCompileOnly("com.terraformersmc:modmenu:${rootProject.property("modmenu_version")}") {
         exclude(group = Groups.FabricApi, module = "fabric-resource-loader-v0")
     })
     implementation(project(path = ":common")) { isTransitive = false }
     add("developmentFabric", project(path = ":common")) { isTransitive = false }
-    shadow(project(path = ":common", configuration = "transformProductionFabric")) { isTransitive = false }
+    shadowC(project(path = ":common", configuration = "transformProductionFabric")) { isTransitive = false }
 }; loom { silentMojangMappingsLicense() }
 

forge/build.gradle.kts

@@ -4,5 +4,5 @@ dependencies {
     forge("net.minecraftforge:forge:${rootProject.architectury.minecraft}-${rootProject.property("forge_version")}")
     implementation(project(path = ":common")) { isTransitive = false }
     add("developmentForge", project(path = ":common")) { isTransitive = false }
-    shadow(project(path = ":common", configuration = "transformProductionForge")) { isTransitive = false }
-}; loom { silentMojangMappingsLicense() }
+    shadowC(project(path = ":common", configuration = "transformProductionForge")) { isTransitive = false }
+}; loom { silentMojangMappingsLicense(); useFabricMixin = true }