From b5a5ec6a821e77f0168bb613e998efaf268b457f Mon Sep 17 00:00:00 2001
From: Neko <neko@ayaka.moe>
Date: Wed, 6 Aug 2025 18:21:12 +0800
Subject: [PATCH] fix(stage-ui): auto eye blink wasn't functioning (#352)

---
 .../src/components/Scenes/Live2D/Model.vue    | 65 ++++++++++++++++---
 1 file changed, 55 insertions(+), 10 deletions(-)

diff --git a/packages/stage-ui/src/components/Scenes/Live2D/Model.vue b/packages/stage-ui/src/components/Scenes/Live2D/Model.vue
index 04b3888b0..4ab52a5d4 100644
--- a/packages/stage-ui/src/components/Scenes/Live2D/Model.vue
+++ b/packages/stage-ui/src/components/Scenes/Live2D/Model.vue
@@ -1,5 +1,6 @@
 <script setup lang="ts">
 import type { Application } from '@pixi/app'
+import type { Cubism4InternalModel, InternalModel } from 'pixi-live2d-display/cubism4'
 
 import localforage from 'localforage'
 
@@ -16,6 +17,13 @@ import { computed, onMounted, onUnmounted, ref, shallowRef, toRef, watch } from
 import { useLive2DIdleEyeFocus } from '../../../composables/live2d'
 import { useLive2d, useSettings } from '../../../stores'
 
+type CubismModel = Cubism4InternalModel['coreModel']
+type CubismEyeBlink = Cubism4InternalModel['eyeBlink']
+type PixiLive2DInternalModel = InternalModel & {
+  eyeBlink?: CubismEyeBlink
+  coreModel: CubismModel
+}
+
 const props = withDefaults(defineProps<{
   app?: Application
   mouthOpenSize?: number
@@ -61,10 +69,11 @@ const offset = computed(() => parsePropsOffset())
 const pixiApp = toRef(() => props.app)
 const paused = toRef(() => props.paused)
 const focusAt = toRef(() => props.focusAt)
-const model = ref<Live2DModel>()
+const model = ref<Live2DModel<PixiLive2DInternalModel>>()
 const initialModelWidth = ref<number>(0)
 const initialModelHeight = ref<number>(0)
 const mouthOpenSize = computed(() => Math.max(0, Math.min(100, props.mouthOpenSize)))
+const lastUpdateTime = ref(0)
 
 const dark = useDark()
 const breakpoints = useBreakpoints(breakpointsTailwind)
@@ -126,7 +135,7 @@ async function loadModel() {
     model.value = undefined
   }
 
-  const modelInstance = new Live2DModel()
+  const modelInstance = new Live2DModel<PixiLive2DInternalModel>()
 
   if (loadSource.value === 'file') {
     await Live2DFactory.setupLive2DModel(modelInstance, [modelFile.value], { autoInteract: false })
@@ -149,7 +158,7 @@ async function loadModel() {
   })
 
   const internalModel = model.value.internalModel
-  const coreModel = internalModel.coreModel as any
+  const coreModel = internalModel.coreModel
   const motionManager = internalModel.motionManager
   coreModel.setParameterValueById('ParamMouthOpenY', mouthOpenSize.value)
 
@@ -179,15 +188,51 @@ async function loadModel() {
   }
 
   // This is hacky too
-  const hookedUpdate = motionManager.update
-  motionManager.update = function (model, now) {
-    hookedUpdate?.call(this, model, now)
-    // Only update eye focus when the model is idle
-    if (motionManager.state.currentGroup === motionManager.groups.idle) {
-      idleEyeFocus.update(internalModel, now)
+  const hookedUpdate = motionManager.update as (model: CubismModel, now: number) => boolean
+  motionManager.update = function (model: CubismModel, now: number) {
+    // Let's initialize the last update time first
+    if (lastUpdateTime.value === 0) {
+      lastUpdateTime.value = now
     }
 
-    return true
+    hookedUpdate?.call(this, model, now)
+    // Possibility 1: Only update eye focus when the model is idle
+    // Possibility 2: For models having no motion groups, currentGroup will be undefined while groups can be { idle: ... }
+    if (!motionManager.state.currentGroup || motionManager.state.currentGroup === motionManager.groups.idle) {
+      idleEyeFocus.update(internalModel, now)
+
+      // If the model has eye blink parameters
+      if (internalModel.eyeBlink != null) {
+        // For the part of the auto eye blink implementation in pixi-live2d-display
+        //
+        // this.emit("beforeMotionUpdate");
+        // const motionUpdated = this.motionManager.update(this.coreModel, now);
+        // this.emit("afterMotionUpdate");
+        // model.saveParameters();
+        // this.motionManager.expressionManager?.update(model, now);
+        // if (!motionUpdated) {
+        //   this.eyeBlink?.updateParameters(model, dt);
+        // }
+        //
+        // https://github.com/guansss/pixi-live2d-display/blob/31317b37d5e22955a44d5b11f37f421e94a11269/src/cubism4/Cubism4InternalModel.ts#L202-L214
+        //
+        // If the this.motionManager.update returns true, as motion updated flag on,
+        // the eye blink parameters will not be updated, in another hand, the auto eye blink is disabled
+        //
+        // Since we are hooking the motionManager.update method currently,
+        // and previously a always `true` was returned, eye blink parameters were never updated.
+        //
+        // Thous we are here to manually update the eye blink parameters within this hooked method
+        internalModel.eyeBlink.updateParameters(model, (now - lastUpdateTime.value) / 1000)
+      }
+
+      // still, mark the motion as updated
+      return true
+    }
+
+    lastUpdateTime.value = now
+
+    return false
   }
 
   motionManager.on('motionStart', (group, index) => {