From a6366f9e42836b4c5732141bf314489ede9f60cb Mon Sep 17 00:00:00 2001
From: Clauderic Demers <clauderic.d@gmail.com>
Date: Tue, 16 Jul 2024 16:25:29 -0400
Subject: [PATCH] Improve shape intersection

---
 .changeset/improve-shape-intersection.md             |  5 +++++
 .../collision/src/algorithms/shapeIntersection.ts    | 12 ++++++++----
 2 files changed, 13 insertions(+), 4 deletions(-)
 create mode 100644 .changeset/improve-shape-intersection.md

diff --git a/.changeset/improve-shape-intersection.md b/.changeset/improve-shape-intersection.md
new file mode 100644
index 00000000..39d17dc1
--- /dev/null
+++ b/.changeset/improve-shape-intersection.md
@@ -0,0 +1,5 @@
+---
+'@dnd-kit/collision': patch
+---
+
+Improve accuracy of `shapeIntersection` when there are multiple intersecting shapes.
diff --git a/packages/collision/src/algorithms/shapeIntersection.ts b/packages/collision/src/algorithms/shapeIntersection.ts
index ed0b375b..e8a0e0d6 100644
--- a/packages/collision/src/algorithms/shapeIntersection.ts
+++ b/packages/collision/src/algorithms/shapeIntersection.ts
@@ -10,12 +10,13 @@ export const shapeIntersection: CollisionDetector = ({
   dragOperation,
   droppable,
 }) => {
-  if (!droppable.shape) {
+  const {shape} = dragOperation;
+
+  if (!droppable.shape || !shape?.current) {
     return null;
   }
 
-  const {shape} = dragOperation;
-  const intersectionArea = shape?.current.intersectionArea(droppable.shape);
+  const intersectionArea = shape.current.intersectionArea(droppable.shape);
 
   // Check if the droppable is intersecting with the drag operation shape.
   if (intersectionArea) {
@@ -26,8 +27,11 @@ export const shapeIntersection: CollisionDetector = ({
      * collisions.
      */
     const distance = Point.distance(droppable.shape.center, position.current);
+    const intersectionRatio =
+      intersectionArea /
+      (shape.current.area + droppable.shape.area - intersectionArea);
 
-    const value = 1 / distance;
+    const value = intersectionRatio / distance;
 
     return {
       id: droppable.id,