Add coloring api

src/main/kotlin/org/polyfrost/polyhitbox/api/HitboxColors.kt

@@ -0,0 +1,56 @@
+package org.polyfrost.polyhitbox.api
+
+import net.minecraft.world.entity.Entity
+import org.slf4j.LoggerFactory
+
+enum class HitboxElement {
+    SIDE,
+    OUTLINE,
+    EYE_HEIGHT,
+    VIEW_RAY,
+}
+
+enum class HitboxCondition {
+    HOVERED,
+    IFRAME,
+}
+
+interface HitboxColorContext {
+    val entity: Entity
+    val element: HitboxElement
+
+    fun has(condition: HitboxCondition): Boolean
+}
+
+fun interface HitboxColorProvider {
+    fun color(context: HitboxColorContext, argb: Int): Int
+}
+
+object HitboxColors {
+
+    private val logger = LoggerFactory.getLogger("PolyHitbox")
+
+    @Volatile
+    private var providers: Array<HitboxColorProvider> = emptyArray()
+
+    @JvmStatic
+    fun register(provider: HitboxColorProvider) {
+        synchronized(this) {
+            if (providers.none { it === provider }) providers += provider
+        }
+    }
+
+    @JvmStatic
+    fun unregister(provider: HitboxColorProvider) {
+        synchronized(this) {
+            providers = providers.filterNot { it === provider }.toTypedArray()
+        }
+    }
+
+    internal fun snapshot(): Array<HitboxColorProvider> = providers
+
+    internal fun disable(provider: HitboxColorProvider, error: Throwable) {
+        unregister(provider)
+        logger.error("Unregistered hitbox color provider {} because it threw.", provider.javaClass.name, error)
+    }
+}

src/main/kotlin/org/polyfrost/polyhitbox/render/HitboxRenderer.kt

@@ -9,6 +9,11 @@ import net.minecraft.util.Mth
 import net.minecraft.world.entity.Entity
 import net.minecraft.world.entity.LivingEntity
 import net.minecraft.world.entity.player.Player
+import org.polyfrost.polyhitbox.api.HitboxColorContext
+import org.polyfrost.polyhitbox.api.HitboxColorProvider
+import org.polyfrost.polyhitbox.api.HitboxColors
+import org.polyfrost.polyhitbox.api.HitboxCondition
+import org.polyfrost.polyhitbox.api.HitboxElement
 import org.polyfrost.polyhitbox.config.HitboxCategory
 import org.polyfrost.polyhitbox.config.HitboxConfig
 import org.polyfrost.polyhitbox.config.ModConfig
@@ -51,6 +56,7 @@ object HitboxRenderer {
     private var viewer: Player? = null
     private var selfInFirstPerson: Entity? = null
     private var vanillaToggle = false
+    private var colorProviders: Array<HitboxColorProvider> = emptyArray()
 
     private var offX = 0.0
     private var offY = 0.0
@@ -140,6 +146,7 @@ object HitboxRenderer {
         viewer = player
         selfInFirstPerson = if (mc.options.cameraType.isFirstPerson) mc.cameraEntity else null
         vanillaToggle = vanillaHitboxesEnabled()
+        colorProviders = HitboxColors.snapshot()
         return true
     }
 
@@ -203,6 +210,36 @@ object HitboxRenderer {
     private fun pick(iframe: Boolean, hover: Boolean, iframeArgb: Int, hoverArgb: Int, baseArgb: Int): Int =
         if (iframe) iframeArgb else if (hover) hoverArgb else baseArgb
 
+    private class Context(
+        override val entity: Entity,
+        override val element: HitboxElement,
+        private val hovered: Boolean,
+        private val iframe: Boolean,
+    ) : HitboxColorContext {
+        override fun has(condition: HitboxCondition): Boolean = when (condition) {
+            HitboxCondition.HOVERED -> hovered
+            HitboxCondition.IFRAME -> iframe
+        }
+    }
+
+    private fun tint(entity: Entity, element: HitboxElement, hover: Boolean, iframe: Boolean, argb: Int): Int {
+        val providers = colorProviders
+        if (providers.isEmpty()) return argb
+        val context = Context(entity, element, hover, iframe)
+        var result = argb
+        var failed = false
+        for (provider in providers) {
+            try {
+                result = provider.color(context, result)
+            } catch (error: Throwable) {
+                HitboxColors.disable(provider, error)
+                failed = true
+            }
+        }
+        if (failed) colorProviders = HitboxColors.snapshot()
+        return result
+    }
+
     private fun drawEntity(vc: VertexConsumer, entity: Entity, config: HitboxConfig) {
         val delta = partialTicks.toDouble()
         val px = Mth.lerp(delta, entity.xo, entity.x)
@@ -223,20 +260,20 @@ object HitboxRenderer {
         val iframe = config.iframeColor && inIframes(entity)
 
         if (config.showSide) {
-            val c = pick(iframe, hover, config.sideIframeArgb, config.sideHoverArgb, config.sideArgb)
+            val c = tint(entity, HitboxElement.SIDE, hover, iframe, pick(iframe, hover, config.sideIframeArgb, config.sideHoverArgb, config.sideArgb))
             fillBox(vc, minX, minY, minZ, maxX, maxY, maxZ, c)
         }
         if (config.showOutline) {
-            val c = pick(iframe, hover, config.outlineIframeArgb, config.outlineHoverArgb, config.outlineArgb)
+            val c = tint(entity, HitboxElement.OUTLINE, hover, iframe, pick(iframe, hover, config.outlineIframeArgb, config.outlineHoverArgb, config.outlineArgb))
             styledBox(vc, config, minX, minY, minZ, maxX, maxY, maxZ, c, config.outlineThickness)
         }
         if (config.showEyeHeight) {
-            val c = pick(iframe, hover, config.eyeHeightIframeArgb, config.eyeHeightHoverArgb, config.eyeHeightArgb)
+            val c = tint(entity, HitboxElement.EYE_HEIGHT, hover, iframe, pick(iframe, hover, config.eyeHeightIframeArgb, config.eyeHeightHoverArgb, config.eyeHeightArgb))
             val eyeY = minY + entity.eyeHeight
             styledBox(vc, config, minX, eyeY - 0.01, minZ, maxX, eyeY + 0.01, maxZ, c, config.eyeHeightThickness)
         }
         if (config.showViewRay) {
-            val c = pick(iframe, hover, config.viewRayIframeArgb, config.viewRayHoverArgb, config.viewRayArgb)
+            val c = tint(entity, HitboxElement.VIEW_RAY, hover, iframe, pick(iframe, hover, config.viewRayIframeArgb, config.viewRayHoverArgb, config.viewRayArgb))
             val eyeY = minY + entity.eyeHeight
             val view = entity.getViewVector(partialTicks)
             val ax = px - camX