single item grabbing, handle stickygrabbable holding basic grabbable

- added single item grabbing to avoid grabbing group of objects
- added ability to let go of objects on a basic grabbable when a sticky grabbable is holding a basic grabbable

Author: dariol

Assets/HTC.UnityPlugin/ViveInputUtility/Scripts/Misc/BasicGrabbable.cs

@@ -16,6 +16,7 @@ public class BasicGrabbable : GrabbableBase<BasicGrabbable.Grabber>
         , IColliderEventDragFixedUpdateHandler
         , IColliderEventDragUpdateHandler
         , IColliderEventDragEndHandler
+		, IColliderEventPressUpHandler
     {
         [Serializable]
         public class UnityEventGrabbable : UnityEvent<BasicGrabbable> { }
@@ -54,7 +55,8 @@ public RigidPose grabberOrigin
 
             public RigidPose grabOffset { get; set; }
         }
-
+		[Tooltip("StickyGrabbable grabbing this BasicGrabbable")]
+        public StickyGrabbable stickyGrabbable;
         private IndexedTable<ColliderButtonEventData, Grabber> m_eventGrabberSet;
 
         public bool alignPosition;
@@ -73,6 +75,8 @@ public RigidPose grabberOrigin
         [SerializeField]
         private bool m_unblockableGrab = true;
         [SerializeField]
+        private bool m_singleItemGrab = false;
+        [SerializeField]
         [FlagsFromEnum(typeof(ControllerButton))]
         private ulong m_primaryGrabButton = 0ul;
         [SerializeField]
@@ -99,6 +103,8 @@ public RigidPose grabberOrigin
 
         public bool unblockableGrab { get { return m_unblockableGrab; } set { m_unblockableGrab = value; } }
 
+        public bool singleItemGrab { get { return m_singleItemGrab; } set { m_singleItemGrab = value; } }
+
         public UnityEventGrabbable afterGrabbed { get { return m_afterGrabbed; } }
 
         public UnityEventGrabbable beforeRelease { get { return m_beforeRelease; } }
@@ -166,7 +172,8 @@ protected override void Awake()
 
         protected virtual void OnDisable()
         {
-            ClearGrabbers(true);
+        	if (!m_allowMultipleGrabbers)
+            	ClearGrabbers(true);
             ClearEventGrabberSet();
         }
 
@@ -196,7 +203,10 @@ protected bool IsValidGrabButton(ColliderButtonEventData eventData)
         public virtual void OnColliderEventDragStart(ColliderButtonEventData eventData)
         {
             if (!IsValidGrabButton(eventData)) { return; }
-
+            if(singleItemGrab) {
+            	ViveColliderEventCaster caster = eventData.eventCaster as ViveColliderEventCaster;
+            	if (!caster.canGrab) { return; }
+        	}
             if (!m_allowMultipleGrabbers)
             {
                 ClearGrabbers(false);
@@ -212,6 +222,12 @@ public virtual void OnColliderEventDragStart(ColliderButtonEventData eventData)
             if (m_eventGrabberSet == null) { m_eventGrabberSet = new IndexedTable<ColliderButtonEventData, Grabber>(); }
             m_eventGrabberSet.Add(eventData, grabber);
 
+            if (singleItemGrab)
+            {
+                ViveColliderEventCaster caster = eventData.eventCaster as ViveColliderEventCaster;
+                caster.canGrab = false;
+            }
+
             AddGrabber(grabber);
         }
 
@@ -235,13 +251,40 @@ public virtual void OnColliderEventDragUpdate(ColliderButtonEventData eventData)
         public virtual void OnColliderEventDragEnd(ColliderButtonEventData eventData)
         {
             if (m_eventGrabberSet == null) { return; }
-
+			if (!IsValidGrabButton(eventData)) { return; }
             Grabber grabber;
             if (!m_eventGrabberSet.TryGetValue(eventData, out grabber)) { return; }
 
             RemoveGrabber(grabber);
             m_eventGrabberSet.Remove(eventData);
             Grabber.Release(grabber);
+            if(singleItemGrab) {
+            	ViveColliderEventCaster caster = eventData.eventCaster as ViveColliderEventCaster;
+            	caster.canGrab = true;
+        	}
+        }
+        public void ForceRelease()
+        {
+            ClearEventGrabberSet();
+            m_beforeRelease.Invoke(this);
+        }
+
+        public void OnColliderEventPressUp(ColliderButtonEventData eventData)
+        {
+            if (stickyGrabbable!=null && stickyGrabbable.isGrabbed)
+            {
+                ForceRelease();
+            }
+            if(singleItemGrab) {
+            	if (!IsValidGrabButton(eventData)) { return; }
+            	ViveColliderEventCaster caster = eventData.eventCaster as ViveColliderEventCaster;
+            	if (isGrabbed)
+            	{
+                	caster.canGrab = true;
+                	m_onDrop?.Invoke(this);
+            	}
+            	caster.canGrab = true;
+        	}
         }
     }
 }

Assets/HTC.UnityPlugin/ViveInputUtility/Scripts/ViveColliderEvent/ViveColliderEventCaster.cs

@@ -32,7 +32,9 @@ public class ViveColliderEventCaster : ColliderEventCaster, IViveRoleComponent
         private ScrollType m_scrollType = ScrollType.Auto;
         [SerializeField]
         private Vector2 m_scrollDeltaScale = new Vector2(1f, -1f);
-
+        [SerializeField]
+        private bool m_canGrab = true;
+        public bool canGrab { get { return m_canGrab; } set { m_canGrab = value; } }
         public ViveRoleProperty viveRole { get { return m_viveRole; } }
         public ScrollType scrollType { get { return m_scrollType; } set { m_scrollType = value; } }
         public Vector2 scrollDeltaScale { get { return m_scrollDeltaScale; } set { m_scrollDeltaScale = value; } }