fix: restore automatic idle motion resume by implementing state-based transition

Author: Eatgrapes

binding/src/main/java/dev/eatgrapes/live2d/CubismUserModel.java

@@ -49,6 +49,9 @@ private void onMotionFinished(String name) {
         }
     }
 
+    public boolean isMotionFinished() { return isMotionFinishedNative(_ptr); }
+    private static native boolean isMotionFinishedNative(long ptr);
+
     public void update(float deltaTime) { updateNative(_ptr, deltaTime); }
     private static native void updateNative(long ptr, float deltaTime);
 

example/src/main/java/dev/eatgrapes/live2d/example/Main.java

@@ -89,9 +89,6 @@ private void setup() throws Exception {
 
         motions.put("idle", load("/model/Hiyori/motions/Hiyori_m01.motion3.json"));
         motions.put("m04", load("/model/Hiyori/motions/Hiyori_m04.motion3.json"));
-
-        // Start background idle loop once at priority 1
-        model.startMotion(motions.get("idle"), 1, true, null);
     }
 
     private void loop() {
@@ -107,6 +104,11 @@ private void loop() {
                 mvp[0] = 1.0f / aspect; mvp[5] = 1.0f; mvp[10] = 1.0f; mvp[15] = 1.0f;
             }
 
+            // Standard state machine: if nothing is playing, play idle
+            if (model.isMotionFinished()) {
+                model.startMotion(motions.get("idle"), 1, false, null);
+            }
+
             model.update(0.016f);
             model.draw(mvp);
             glfwSwapBuffers(window);

native/src/CubismUserModel_JNI.cpp

@@ -70,6 +70,7 @@ class JniUserModel : public CubismUserModel {
     void update(float dt) {
         if (!_model) return;
 
+        // Cleanup finished motions safely
         {
             std::lock_guard<std::mutex> lock(_pendingMutex);
             for (auto* m : _pendingDeletion) {
@@ -83,7 +84,13 @@ class JniUserModel : public CubismUserModel {
         }
 
         _model->LoadParameters();
-        _motionManager->UpdateMotion(_model, dt);
+        
+        // Update motion and check if we are idle
+        bool isMotionPlaying = !_motionManager->IsFinished();
+        if (isMotionPlaying) {
+            _motionManager->UpdateMotion(_model, dt);
+        }
+        
         _model->SaveParameters();
 
         if (_pose) _pose->UpdateParameters(_model, dt);
@@ -101,6 +108,10 @@ class JniUserModel : public CubismUserModel {
         _model->Update();
     }
 
+    bool isMotionFinished() {
+        return _motionManager->IsFinished();
+    }
+
     void notifyFinished() {
         JNIEnv* env = getEnv();
         if (!env || !_javaObj) return;
@@ -205,6 +216,10 @@ JNIEXPORT void JNICALL Java_dev_eatgrapes_live2d_CubismUserModel_startMotionNati
     env->ReleaseByteArrayElements(buffer, data, JNI_ABORT);
 }
 
+JNIEXPORT jboolean JNICALL Java_dev_eatgrapes_live2d_CubismUserModel_isMotionFinishedNative(JNIEnv*, jclass, jlong ptr) {
+    return ((JniUserModel*)ptr)->isMotionFinished();
+}
+
 JNIEXPORT void JNICALL Java_dev_eatgrapes_live2d_CubismUserModel_updateNative(JNIEnv*, jclass, jlong ptr, jfloat dt) {
     ((JniUserModel*)ptr)->update(dt);
 }
@@ -243,4 +258,4 @@ JNIEXPORT void JNICALL Java_dev_eatgrapes_live2d_CubismUserModel_drawNative(JNIE
     env->ReleaseFloatArrayElements(matrix, m_ptr, JNI_ABORT);
 }
 
-}
+}