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Assets/Packages/com.unity.uiextensions/Runtime/Scripts/Utilities/UILineConnector.cs

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+/// Credit Alastair Aitchison
+/// Sourced from - https://bitbucket.org/UnityUIExtensions/unity-ui-extensions/issues/123/uilinerenderer-issues-with-specifying
+
+namespace UnityEngine.UI.Extensions
+{
+    [AddComponentMenu("UI/Extensions/UI Line Connector")]
+    [RequireComponent(typeof(UILineRenderer))]
+    [ExecuteInEditMode]
+    public class UILineConnector : MonoBehaviour
+    {
+
+        // The elements between which line segments should be drawn
+        public RectTransform[] transforms;
+        private Vector3[] previousPositions;
+        private RectTransform canvas;
+        private RectTransform rt;
+        private UILineRenderer lr;
+
+        private void Awake()
+        {
+            var canvasParent = GetComponentInParent<RectTransform>().GetParentCanvas();
+            if (canvasParent != null)
+            {
+                canvas = canvasParent.GetComponent<RectTransform>();
+            }
+            rt = GetComponent<RectTransform>();
+            lr = GetComponent<UILineRenderer>();
+        }
+
+        // Update is called once per frame
+        void Update()
+        {
+            if (transforms == null || transforms.Length < 1)
+            {
+                return;
+            }
+            //Performance check to only redraw when the child transforms move
+            if (previousPositions != null && previousPositions.Length == transforms.Length)
+            {
+                bool updateLine = false;
+                for (int i = 0; i < transforms.Length; i++)
+                {
+                    if (transforms[i] == null)
+                    {
+                        continue;
+                    }
+                    if (!updateLine && previousPositions[i] != transforms[i].position)
+                    {
+                        updateLine = true;
+                    }
+                }
+                if (!updateLine) return;
+            }
+
+            // Get the pivot points
+            Vector2 thisPivot = rt.pivot;
+            Vector2 canvasPivot = canvas.pivot;
+
+            // Set up some arrays of coordinates in various reference systems
+            Vector3[] worldSpaces = new Vector3[transforms.Length];
+            Vector3[] canvasSpaces = new Vector3[transforms.Length];
+            Vector2[] points = new Vector2[transforms.Length];
+
+            // First, convert the pivot to worldspace
+            for (int i = 0; i < transforms.Length; i++)
+            {
+                if (transforms[i] == null)
+                {
+                    continue;
+                }
+                worldSpaces[i] = transforms[i].TransformPoint(thisPivot);
+            }
+
+            // Then, convert to canvas space
+            for (int i = 0; i < transforms.Length; i++)
+            {
+                canvasSpaces[i] = canvas.InverseTransformPoint(worldSpaces[i]);
+            }
+
+            // Calculate delta from the canvas pivot point
+            for (int i = 0; i < transforms.Length; i++)
+            {
+                points[i] = new Vector2(canvasSpaces[i].x, canvasSpaces[i].y);
+            }
+
+            // And assign the converted points to the line renderer
+            lr.Points = points;
+            lr.RelativeSize = false;
+            lr.drivenExternally = true;
+
+            previousPositions = new Vector3[transforms.Length];
+            for (int i = 0; i < transforms.Length; i++)
+            {
+                if (transforms[i] == null)
+                {
+                    continue;
+                }
+                previousPositions[i] = transforms[i].position;
+            }
+        }
+    }
+}