Updated ScrollSnap with fixes from author

--HG--
branch : develop_4.6

Scripts/Layout/ScrollSnap.cs

@@ -9,7 +9,6 @@
 ///   if you dont wish to use this auto resize turn of autoLayoutItems
 /// - fixed current page made it independant from pivot
 /// - replaced pagination with delegate function
-
 using System;
 using UnityEngine.EventSystems;
 
@@ -22,10 +21,11 @@ namespace UnityEngine.UI.Extensions
 	{
 		// needed becouse of reversed behavior of axis Y compared to X
 		// (positions of children lower in children list in horizontal directions grows when in vertical it gets smaller)
-		public enum ScrollDirection {
+		public enum ScrollDirection
+		{
 			Horizontal,
 			Vertical
-		};
+		}
 
 		public delegate void PageSnapChange(int page);
 
@@ -34,11 +34,12 @@ namespace UnityEngine.UI.Extensions
 		public ScrollDirection direction = ScrollDirection.Horizontal;
 
 		protected ScrollRect scrollRect;
-		protected RectTransform scrollRectTransform;
-		protected Transform listContainerTransform;
-		protected RectTransform rectTransform;
 
-		protected int items = 0;
+		protected RectTransform scrollRectTransform;
+
+		protected Transform listContainerTransform;
+
+		protected RectTransform rectTransform;
 
 		int pages;
 
@@ -46,22 +47,31 @@ namespace UnityEngine.UI.Extensions
 
 		// anchor points to lerp to to see child on certain indexes
 		protected Vector3[] pageAnchorPositions;
+
 		protected Vector3 lerpTarget;
+
 		protected bool lerp;
 
 		// item list related
 		protected float listContainerMinPosition;
+
 		protected float listContainerMaxPosition;
+
 		protected float listContainerSize;
+
 		protected RectTransform listContainerRectTransform;
+
 		protected Vector2 listContainerCachedSize;
 
 		protected float itemSize;
 		
+		protected int itemsCount = 0;
+
 		[Tooltip("Button to go to the next page. (optional)")]
-        public GameObject nextButton;
+		public Button nextButton;
+
 		[Tooltip("Button to go to the previous page. (optional)")]
-		public GameObject prevButton;
+		public Button prevButton;
 		
 		[Tooltip("Number of items visible in one page of scroll frame.")]
 		[RangeAttribute(1,100)]
@@ -73,20 +83,28 @@ namespace UnityEngine.UI.Extensions
 		[Tooltip("If you wish to update scrollbar numberOfSteps to number of active children on list.")]
 		public bool linkScrolbarSteps = false;
 		
+		[Tooltip("If you wish to update scrollrect sensitivity to size of list element.")]
+		public bool linkScrolrectScrollSensitivity = false;
+
 		public Boolean useFastSwipe = true;
+
 		public int fastSwipeThreshold = 100;
 
 		// drag related
 		protected bool startDrag = true;
+
 		protected Vector3 positionOnDragStart = new Vector3();
+
 		protected int pageOnDragStart;
 		
 		protected bool fastSwipeTimer = false;
+
 		protected int fastSwipeCounter = 0;
+
 		protected int fastSwipeTarget = 10;
 
 		// Use this for initialization
-		void Start()
+		void Awake()
 		{
 			lerp = false;
 
@@ -103,30 +121,45 @@ namespace UnityEngine.UI.Extensions
 
 			if (nextButton)
 			{
-				nextButton.GetComponent<Button> ().onClick.AddListener (() => { NextScreen (); });
+				nextButton.GetComponent<Button>().onClick.AddListener(() => {
+					NextScreen(); });
 			}
 
 			if (prevButton)
 			{
-				prevButton.GetComponent<Button> ().onClick.AddListener (() => { PreviousScreen (); });
+				prevButton.GetComponent<Button>().onClick.AddListener(() => {
+					PreviousScreen(); });
 			}
 		}
 
+		void Start()
+		{
+			Awake();
+		}
+
 		public void UpdateListItemsSize()
 		{
 			float size = 0;
+			float currentSize = 0;
 			if (direction == ScrollSnap.ScrollDirection.Horizontal)
 			{
 				size = scrollRectTransform.rect.width / itemsVisibleAtOnce;
+				currentSize = listContainerRectTransform.rect.width / itemsCount;
 			}
 			else
 			{
 				size = scrollRectTransform.rect.height / itemsVisibleAtOnce;
+				currentSize = listContainerRectTransform.rect.height / itemsCount;
 			}
 
 			itemSize = size;
 
-			if (autoLayoutItems && size != itemSize)
+			if (linkScrolrectScrollSensitivity)
+			{
+				scrollRect.scrollSensitivity = itemSize;
+			}
+
+			if (autoLayoutItems && currentSize != size && itemsCount > 0)
 			{
 				if (direction == ScrollSnap.ScrollDirection.Horizontal)
 				{
@@ -174,14 +207,16 @@ namespace UnityEngine.UI.Extensions
 				// checking how many children of list are active
 				int activeCount = 0;
 				
-				foreach (var tr in listContainerTransform) {
+				foreach (var tr in listContainerTransform)
-					if (((Transform)tr).gameObject.activeInHierarchy) {
+				{
+					if (((Transform) tr).gameObject.activeInHierarchy)
+					{
 						activeCount++;
 					}
 				}
 
 				// if anything changed since last check reinitialize anchors list
-				items = 0;
+				itemsCount = 0;
 				Array.Resize(ref pageAnchorPositions, activeCount);
 
 				if (activeCount > 0)
@@ -190,6 +225,7 @@ namespace UnityEngine.UI.Extensions
 
 					if (direction == ScrollDirection.Horizontal)
 					{
+						//Debug.Log ("-------------looking for list spanning range----------------");
 						// looking for list spanning range min/max
 						scrollRect.horizontalNormalizedPosition = 0;
 						listContainerMaxPosition = listContainerTransform.localPosition.x;
@@ -197,6 +233,8 @@ namespace UnityEngine.UI.Extensions
 						listContainerMinPosition = listContainerTransform.localPosition.x;
 						
 						listContainerSize = listContainerMaxPosition - listContainerMinPosition;
+						//itemSize = pages > 1 ? listContainerSize / (float)(pages - 1) : listContainerSize / activeCount;
+						//itemSize *= (pages + itemsVisibleAtOnce) / (pages + 1);
 
 						for (var i = 0; i < pages; i ++)
 						{
@@ -206,9 +244,12 @@ namespace UnityEngine.UI.Extensions
 								listContainerTransform.localPosition.z
 							);
 						}
+						
+						//Debug.Log (String.Format("min:{0:0.0}, max:{1:0.0}, pages: {2:0}, width: {3:0}", listContainerMinPosition, listContainerMaxPosition, pages, listContainerSize/pages));
 					}
 					else
 					{
+						//Debug.Log ("-------------looking for list spanning range----------------");
 						// looking for list spanning range
 						scrollRect.verticalNormalizedPosition = 1;
 						listContainerMinPosition = listContainerTransform.localPosition.y;
@@ -216,6 +257,8 @@ namespace UnityEngine.UI.Extensions
 						listContainerMaxPosition = listContainerTransform.localPosition.y;
 						
 						listContainerSize = listContainerMaxPosition - listContainerMinPosition;
+						//itemSize = pages > 1 ? listContainerSize / (float)(pages - 1) : listContainerSize / activeCount;
+						//itemSize *= (pages + itemsVisibleAtOnce) / (pages + 1);
 
 						for (var i = 0; i < pages; i ++)
 						{
@@ -224,21 +267,23 @@ namespace UnityEngine.UI.Extensions
 								listContainerMinPosition + itemSize * i,
 								listContainerTransform.localPosition.z
 							);
+							//Debug.Log (String.Format("pos[{0:0}]={1} {2:0%}", i, pageAnchorPositions[i], pages > 1 ? i/(float)(pages-1) : (float)i));
 						}
 
-						foreach (var tr in listContainerTransform) {
+						//Debug.Log (String.Format("min:{0:0.0}, max:{1:0.0}, pages: {2:0}, width: {3:0}", listContainerMinPosition, listContainerMaxPosition, pages, listContainerSize/pages));
-							if (((Transform)tr).gameObject.activeInHierarchy) {
-								activeCount++;
-							}
-						}
-
 					}
 
 					UpdateScrollbar(linkScrolbarSteps);
 					startingPage = Mathf.Min(startingPage, pages);
 					ResetPage();
 				}
-				items = activeCount;
+
+				if (itemsCount != activeCount)
+				{
+					ChangePage(CurrentPage());
+				}
+
+				itemsCount = activeCount;
 				listContainerCachedSize.Set(listContainerRectTransform.rect.size.x, listContainerRectTransform.rect.size.y); 
 			}
 
@@ -294,7 +339,7 @@ namespace UnityEngine.UI.Extensions
 			}
 		}
 
-        void Update()
+		void LateUpdate()
 		{
 			UpdateListItemsSize();
 			UpdateListItemPositions();
@@ -311,6 +356,8 @@ namespace UnityEngine.UI.Extensions
 					lerp = false;
 					
 					UpdateScrollbar(linkScrolbarSteps);
+					
+					//Debug.Log(String.Format("Lerp: {0}/{1} page: {2:0}", lerpTarget, listContainerTransform.localPosition, CurrentPage()));
 				}
 
 				//change the info bullets at the bottom of the screen. Just for visual effect
@@ -324,6 +371,8 @@ namespace UnityEngine.UI.Extensions
 			{
 				fastSwipeCounter++;
 			}
+			
+			//Debug.Log(String.Format("Update: {0}", listContainerTransform.localPosition));
 		}
 
 		private bool fastSwipe = false; //to determine if a fast swipe was performed
@@ -404,6 +453,8 @@ namespace UnityEngine.UI.Extensions
 
 			float page = pos / itemSize;
 
+			//Debug.Log (String.Format("min:{0:0.0}, max:{1:0.0}, current:{2:0.0}/{4:0.0}, page:{3:0.0}, target:{5}", listContainerMinPosition, listContainerMaxPosition, pos, page, listContainerTransform.localPosition.x, pageAnchorPositions[Mathf.RoundToInt(page)]));
+
 			return Mathf.Clamp(Mathf.RoundToInt(page), 0, pages);
 		}
 
@@ -412,6 +463,16 @@ namespace UnityEngine.UI.Extensions
 		{
 			startingPage = currentPage;
 
+			if (nextButton)
+			{
+				nextButton.interactable = currentPage < pages - 1;
+			}
+			
+			if (prevButton)
+			{
+				prevButton.interactable = currentPage > 0;
+			}
+
 			if (onPageChange != null)
 			{
 				onPageChange(currentPage);
@@ -428,6 +489,8 @@ namespace UnityEngine.UI.Extensions
 
 			positionOnDragStart = eventData.position;
 			pageOnDragStart = CurrentPage();
+
+			//Debug.Log (String.Format("pageOnDragStart:{0:0}", pageOnDragStart));
 		}
 
 		public void OnEndDrag(PointerEventData eventData)