From 8ea50a77fd14752aba5d1e706fdd24866e382c2d Mon Sep 17 00:00:00 2001
From: happy-capybara-man <willyfr4214@gmail.com>
Date: Thu, 18 Dec 2025 01:39:27 +0800
Subject: [PATCH] js: restore deep copy behavior for Mat.clone()

Emscripten 3.1.71+ introduced ClassHandle.clone() which performs a shallow copy.
This shadowed the original OpenCV clone() method which was intended for deep copying.

This patch:
1. Hooks into onRuntimeInitialized in helpers.js
2. Overrides cv.Mat.prototype.clone to point to mat_clone (deep copy)
3. Updates JS tests to use clone() to verify the fix
---
 modules/js/src/helpers.js   | 17 +++++++++++++++++
 modules/js/test/test_mat.js |  2 +-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/modules/js/src/helpers.js b/modules/js/src/helpers.js
index ab88d18eec..67dc8639fa 100644
--- a/modules/js/src/helpers.js
+++ b/modules/js/src/helpers.js
@@ -410,3 +410,20 @@ if (
     if (cv.UMat) cv.UMat.prototype[Symbol.dispose] = cv.UMat.prototype.delete;
     // Add more as OpenCV gains new manual-cleanup classes
 }
+
+// Override Emscripten's shallow clone() with OpenCV's deep copy mat_clone()
+// This restores the expected behavior where clone() performs a deep copy.
+// Background: Emscripten 3.1.71+ added ClassHandle.clone() which only does shallow copy.
+// See: https://github.com/opencv/opencv/pull/26643
+// See: https://github.com/opencv/opencv/issues/27572
+var _opencv_onRuntimeInitialized_backup = Module['onRuntimeInitialized'];
+Module['onRuntimeInitialized'] = function() {
+    if (_opencv_onRuntimeInitialized_backup) {
+        _opencv_onRuntimeInitialized_backup();
+    }
+    if (typeof cv !== 'undefined' && cv.Mat &&
+        typeof cv.Mat.prototype.mat_clone === 'function') {
+        cv.Mat.prototype.clone = cv.Mat.prototype.mat_clone;
+    }
+};
+
diff --git a/modules/js/test/test_mat.js b/modules/js/test/test_mat.js
index f0c5211568..a1d5c98b17 100644
--- a/modules/js/test/test_mat.js
+++ b/modules/js/test/test_mat.js
@@ -173,7 +173,7 @@ QUnit.test('test_mat_creation', function(assert) {
     //   clone
     {
         let mat = cv.Mat.ones(5, 5, cv.CV_8UC1);
-        let mat2 = mat.mat_clone();
+        let mat2 = mat.clone();
 
         assert.equal(mat.channels, mat2.channels);
         assert.equal(mat.size().height, mat2.size().height);