From 1dbbbeced14e992bc0234e4eb3e47db0af4607cd Mon Sep 17 00:00:00 2001
From: stefnotch <brandmairstefan@gmail.com>
Date: Wed, 24 Feb 2021 21:05:10 +0100
Subject: [PATCH] Specialized Visject Connection Broadphase Intersection

---
 Source/Editor/Surface/Elements/OutputBox.cs | 100 +++++++++++++++++++-
 1 file changed, 99 insertions(+), 1 deletion(-)

diff --git a/Source/Editor/Surface/Elements/OutputBox.cs b/Source/Editor/Surface/Elements/OutputBox.cs
index 0c3ba8da4..251d599b8 100644
--- a/Source/Editor/Surface/Elements/OutputBox.cs
+++ b/Source/Editor/Surface/Elements/OutputBox.cs
@@ -2,6 +2,7 @@
 
 using FlaxEngine;
 using FlaxEngine.GUI;
+using System;
 
 namespace FlaxEditor.Surface.Elements
 {
@@ -43,10 +44,86 @@ namespace FlaxEditor.Surface.Elements
             */
         }
 
+        private static bool IsRight(ref Vector2 a, ref Vector2 b, ref Vector2 point)
+        {
+            return ((b.X - a.X) * (point.Y - a.Y) - (b.Y - a.Y) * (point.X - a.X)) <= 0;
+        }
+
+        /// <summary>
+        /// Checks if a point intersects a bezier curve
+        /// </summary>
+        /// <param name="start">The start location.</param>
+        /// <param name="end">The end location.</param>
+        /// <param name="point">The point</param>
+        /// <param name="distance">Distance at which its an intersection</param>
+        public static bool IntersectsConnection(ref Vector2 start, ref Vector2 end, ref Vector2 point, float distance)
+        {
+            if ((point.X - start.X) * (end.X - point.X) < 0) return false;
+
+            var dst = (end - start) * new Vector2(0.25f, 0.05f); // Purposefully tweaked to 0.25
+            Vector2 control1 = new Vector2(start.X + dst.X, start.Y + dst.Y);
+            Vector2 control2 = new Vector2(end.X - dst.X, end.Y + dst.Y);
+
+            // I'm ignoring the start.Y + dst.Y
+
+            Vector2 direction = end - start;
+            float offset = Mathf.Sign(direction.Y) * distance;
+
+            Vector2 pointAbove1 = new Vector2(control1.X, start.Y - offset);
+            Vector2 pointAbove2 = new Vector2(end.X, end.Y - offset);
+            Vector2 pointBelow1 = new Vector2(start.X, start.Y + offset);
+            Vector2 pointBelow2 = new Vector2(control2.X, end.Y + offset);
+
+            /*  Render2D.DrawLine(pointAbove1, pointAbove2, Color.Red);
+              Render2D.DrawRectangle(new Rectangle(pointAbove2 - new Vector2(5), new Vector2(10)), Color.Red);
+              Render2D.DrawLine(pointBelow1, pointBelow2, Color.Green);
+              Render2D.DrawRectangle(new Rectangle(pointBelow2 - new Vector2(5), new Vector2(10)), Color.Green);
+            */
+            // TODO: are they parallel ^?
+
+            return IsRight(ref pointAbove1, ref pointAbove2, ref point) == IsRight(ref pointBelow2, ref pointBelow1, ref point);
+
+
+            // Taken from the Render2D.DrawBezier code
+            float squaredDistance = distance;
+
+            Vector2 d1 = control1 - start;
+            Vector2 d2 = control2 - control1;
+            Vector2 d3 = end - control2;
+            float len = d1.Length + d2.Length + d3.Length;
+            int segmentCount = Math.Min(Math.Max(Mathf.CeilToInt(len * 0.05f), 1), 100);
+            float segmentCountInv = 1.0f / segmentCount;
+
+            Bezier(ref start, ref control1, ref control2, ref end, 0, out Vector2 p);
+            for (int i = 1; i <= segmentCount; i++)
+            {
+                Vector2 oldp = p;
+                float t = i * segmentCountInv;
+                Bezier(ref start, ref control1, ref control2, ref end, t, out p);
+
+                CollisionsHelper.ClosestPointPointLine(ref point, ref oldp, ref p, out Vector2 result);
+                if (Vector2.DistanceSquared(point, result) <= squaredDistance)
+                {
+                    return true;
+                }
+            }
+            return false;
+        }
+
+        private static void Bezier(ref Vector2 p0, ref Vector2 p1, ref Vector2 p2, ref Vector2 p3, float alpha, out Vector2 result)
+        {
+            Vector2.Lerp(ref p0, ref p1, alpha, out var p01);
+            Vector2.Lerp(ref p1, ref p2, alpha, out var p12);
+            Vector2.Lerp(ref p2, ref p3, alpha, out var p23);
+            Vector2.Lerp(ref p01, ref p12, alpha, out var p012);
+            Vector2.Lerp(ref p12, ref p23, alpha, out var p123);
+            Vector2.Lerp(ref p012, ref p123, alpha, out result);
+        }
+
         /// <summary>
         /// Draw all connections coming from this box.
         /// </summary>
-        public void DrawConnections()
+        public void DrawConnections(ref Vector2 mousePosition)
         {
             // Draw all the connections
             var center = Size * 0.5f;
@@ -60,10 +137,31 @@ namespace FlaxEditor.Surface.Elements
                 Vector2 endPos = targetBox.Parent.PointToParent(ref tmp);
                 var highlight = 1 + Mathf.Max(startHighlight, targetBox.ConnectionsHighlightIntensity);
                 var color = _currentTypeColor * highlight;
+
+                // if (PointInRectangle(ref startPos, ref endPos, ref mousePosition))
+                {
+                    for (int ix = 0; ix < 10000; ix++)
+                    {
+                        OutputBox.IntersectsConnection(ref startPos, ref endPos, ref mousePosition, 30f);
+                    }
+                    if (OutputBox.IntersectsConnection(ref startPos, ref endPos, ref mousePosition, 30f))
+                    {
+                        highlight += 2;
+                    }
+                }
+
+
                 DrawConnection(ref startPos, ref endPos, ref color, highlight);
             }
         }
 
+        private bool PointInRectangle(ref Vector2 a, ref Vector2 b, ref Vector2 point)
+        {
+            // This has the convenient property that it doesn't matter if a and b are switched
+            Vector2 signs = (point - a) * (b - point);
+            return signs.X >= 0 && signs.Y >= 0;
+        }
+
         /// <summary>
         /// Draw a selected connections coming from this box.
         /// </summary>