when trigger is squeezed, check for things stuck to hand and unhook them

examples/controllers/handControllerGrab.js

@@ -801,6 +801,8 @@ function MyController(hand) {
         this.isInitialGrab = false;
         this.doubleParentGrab = false;
 
+        this.checkForStrayChildren();
+
         if (this.state == STATE_SEARCHING ? this.triggerSmoothedReleased() : this.bumperReleased()) {
             this.setState(STATE_RELEASE);
             return;
@@ -1751,6 +1753,17 @@ function MyController(hand) {
         return data;
     };
 
+    this.checkForStrayChildren = function() {
+        // sometimes things can get parented to a hand and this script is unaware.  Search for such entities and
+        // unhook them.
+        var handJointIndex = MyAvatar.getJointIndex(this.hand === RIGHT_HAND ? "RightHand" : "LeftHand");
+        var children = Entities.getChildrenIDsOfJoint(MyAvatar.sessionUUID, handJointIndex);
+        children.forEach(function(childID) {
+            print("disconnecting stray child of hand: " + childID);
+            Entities.editEntity(childID, {parentID: NULL_UUID});
+        });
+    }
+
     this.deactivateEntity = function(entityID, noVelocity) {
         var data = getEntityCustomData(GRAB_USER_DATA_KEY, entityID, {});
         if (data && data["refCount"]) {

libraries/entities/src/EntityScriptingInterface.cpp

@@ -12,6 +12,7 @@
 
 #include "EntityItemID.h"
 #include <VariantMapToScriptValue.h>
+#include <SpatialParentFinder.h>
 
 #include "EntitiesLogging.h"
 #include "EntityActionFactoryInterface.h"
@@ -1063,6 +1064,32 @@ QStringList EntityScriptingInterface::getJointNames(const QUuid& entityID) {
     return result;
 }
 
+QVector<QUuid> EntityScriptingInterface::getChildrenIDsOfJoint(const QUuid& parentID, int jointIndex) {
+    QVector<QUuid> result;
+    if (!_entityTree) {
+        return result;
+    }
+    _entityTree->withReadLock([&] {
+        QSharedPointer<SpatialParentFinder> parentFinder = DependencyManager::get<SpatialParentFinder>();
+        if (!parentFinder) {
+            return;
+        }
+        bool success;
+        SpatiallyNestableWeakPointer parentWP = parentFinder->find(parentID, success);
+        if (!success) {
+            return;
+        }
+        SpatiallyNestablePointer parent = parentWP.lock();
+        if (!parent) {
+            return;
+        }
+        parent->forEachChild([&](SpatiallyNestablePointer child) {
+            result.push_back(child->getID());
+        });
+    });
+    return result;
+}
+
 float EntityScriptingInterface::calculateCost(float mass, float oldVelocity, float newVelocity) {
     return std::abs(mass * (newVelocity - oldVelocity));
 }

libraries/entities/src/EntityScriptingInterface.h

@@ -168,7 +168,7 @@ public slots:
 
     Q_INVOKABLE int getJointIndex(const QUuid& entityID, const QString& name);
     Q_INVOKABLE QStringList getJointNames(const QUuid& entityID);
-    
+    Q_INVOKABLE QVector<QUuid> getChildrenIDsOfJoint(const QUuid& parentID, int jointIndex);
 
 signals:
     void collisionWithEntity(const EntityItemID& idA, const EntityItemID& idB, const Collision& collision);