From 017b36aeae075553a95efae23ae2765af6c09961 Mon Sep 17 00:00:00 2001
From: Mark Tolmacs <mark@lazycat.hu>
Date: Fri, 12 Sep 2025 19:19:49 +0200
Subject: [PATCH] fix:More precise element nesting check

---
 packages/element/src/binding.ts   |  8 ++---
 packages/element/src/collision.ts | 55 +++++++++++++++++++++++++++++++
 2 files changed, 59 insertions(+), 4 deletions(-)

diff --git a/packages/element/src/binding.ts b/packages/element/src/binding.ts
index 3301173e2e..acf218d916 100644
--- a/packages/element/src/binding.ts
+++ b/packages/element/src/binding.ts
@@ -1,6 +1,5 @@
 import { KEYS, arrayToMap, invariant, isTransparent } from "@excalidraw/common";
 
-import { isElementInsideBBox } from "@excalidraw/utils";
 import {
   lineSegment,
   pointFrom,
@@ -31,6 +30,7 @@ import {
   getAllHoveredElementAtPoint,
   getHoveredElementForBinding,
   intersectElementWithLineSegment,
+  isBindableElementInsideOtherBindable,
   isPointInElement,
 } from "./collision";
 import { distanceToElement } from "./distance";
@@ -351,7 +351,7 @@ const bindingStrategyForNewSimpleArrowEndpointDragging = (
       // We are hovering another element with the end point
       const isNested =
         hit &&
-        isElementInsideBBox(otherElement, getElementBounds(hit, elementsMap));
+        isBindableElementInsideOtherBindable(otherElement, hit, elementsMap);
       let current: BindingStrategy;
       if (hit) {
         const isInsideBinding =
@@ -424,7 +424,7 @@ const bindingStrategyForSimpleArrowEndpointDragging = (
   const isNested =
     hit &&
     oppositeElement &&
-    isElementInsideBBox(oppositeElement, getElementBounds(hit, elementsMap));
+    isBindableElementInsideOtherBindable(oppositeElement, hit, elementsMap);
 
   // If the global bind mode is in free binding mode, just bind
   // where the pointer is and keep the other end intact
@@ -1267,7 +1267,7 @@ export const updateBoundPoint = (
     compareElementArea(bindableElement, otherBindableElement) < 0;
   const isIntersecting = otherBounds && doBoundsIntersect(bounds, otherBounds);
   // const isNested =
-  //   otherBindableElement && isElementInsideBBox(otherBindableElement, bounds);
+  //   otherBindableElement && isBindableElementInsideOtherBindable(otherBindableElement, bindableElement);
   const isNested = isIntersecting && isLargerThanOther;
 
   const maybeOutlineGlobal =
diff --git a/packages/element/src/collision.ts b/packages/element/src/collision.ts
index ff65417c70..6c711fe153 100644
--- a/packages/element/src/collision.ts
+++ b/packages/element/src/collision.ts
@@ -34,6 +34,7 @@ import {
   elementCenterPoint,
   getCenterForBounds,
   getCubicBezierCurveBound,
+  getDiamondPoints,
   getElementBounds,
 } from "./bounds";
 import {
@@ -657,3 +658,57 @@ export const isPointInElement = (
 
   return intersections.length % 2 === 1;
 };
+
+export const isBindableElementInsideOtherBindable = (
+  innerElement: ExcalidrawBindableElement,
+  outerElement: ExcalidrawBindableElement,
+  elementsMap: ElementsMap,
+): boolean => {
+  // Get corner points of the inner element based on its type
+  const getCornerPoints = (element: ExcalidrawElement): GlobalPoint[] => {
+    const { x, y, width, height, angle } = element;
+    const center = elementCenterPoint(element, elementsMap);
+
+    if (element.type === "diamond") {
+      // Diamond has 4 corner points at the middle of each side
+      const [topX, topY, rightX, rightY, bottomX, bottomY, leftX, leftY] =
+        getDiamondPoints(element);
+      const corners: GlobalPoint[] = [
+        pointFrom(x + topX, y + topY), // top
+        pointFrom(x + rightX, y + rightY), // right
+        pointFrom(x + bottomX, y + bottomY), // bottom
+        pointFrom(x + leftX, y + leftY), // left
+      ];
+      return corners.map((corner) => pointRotateRads(corner, center, angle));
+    }
+    if (element.type === "ellipse") {
+      // For ellipse, test points at the extremes (top, right, bottom, left)
+      const cx = x + width / 2;
+      const cy = y + height / 2;
+      const rx = width / 2;
+      const ry = height / 2;
+      const corners: GlobalPoint[] = [
+        pointFrom(cx, cy - ry), // top
+        pointFrom(cx + rx, cy), // right
+        pointFrom(cx, cy + ry), // bottom
+        pointFrom(cx - rx, cy), // left
+      ];
+      return corners.map((corner) => pointRotateRads(corner, center, angle));
+    }
+    // Rectangle and other rectangular shapes (image, text, etc.)
+    const corners: GlobalPoint[] = [
+      pointFrom(x, y), // top-left
+      pointFrom(x + width, y), // top-right
+      pointFrom(x + width, y + height), // bottom-right
+      pointFrom(x, y + height), // bottom-left
+    ];
+    return corners.map((corner) => pointRotateRads(corner, center, angle));
+  };
+
+  const innerCorners = getCornerPoints(innerElement);
+
+  // Check if all corner points of the inner element are inside the outer element
+  return innerCorners.every((corner) =>
+    isPointInElement(corner, outerElement, elementsMap),
+  );
+};