From 40edd22d114603612e223796f593e1b214035490 Mon Sep 17 00:00:00 2001
From: Dave Aitken <dave.a@goodnotes.com>
Date: Fri, 3 Oct 2025 10:09:10 +0100
Subject: [PATCH 1/3] fix: transform concatenation order

---
 Source/CoreGraphicsPolyfill.swift | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/Source/CoreGraphicsPolyfill.swift b/Source/CoreGraphicsPolyfill.swift
index 36ec038..83c47ad 100644
--- a/Source/CoreGraphicsPolyfill.swift
+++ b/Source/CoreGraphicsPolyfill.swift
@@ -316,12 +316,12 @@ import Foundation
 
         public func concatenating(_ t: CGAffineTransform) -> CGAffineTransform {
             return CGAffineTransform(
-                a: a * t.a + c * t.b,
-                b: b * t.a + d * t.b,
-                c: a * t.c + c * t.d,
-                d: b * t.c + d * t.d,
-                tx: a * t.tx + c * t.ty + tx,
-                ty: b * t.tx + d * t.ty + ty
+                a: a * t.a + b * t.c,
+                b: a * t.b + b * t.d,
+                c: c * t.a + d * t.c,
+                d: c * t.b + d * t.d,
+                tx: tx * t.a + ty * t.c + t.tx,
+                ty: tx * t.b + ty * t.d + t.ty
             )
         }
 

From de77dbab1c63793673ba071b5393b0bd8df67ab3 Mon Sep 17 00:00:00 2001
From: Dave Aitken <dave.a@goodnotes.com>
Date: Fri, 3 Oct 2025 12:10:23 +0100
Subject: [PATCH 2/3] test: update tests for new concat order

---
 Tests/CoreGraphicsPolyfillTests/PolyfillTests.swift | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Tests/CoreGraphicsPolyfillTests/PolyfillTests.swift b/Tests/CoreGraphicsPolyfillTests/PolyfillTests.swift
index 3bab052..86555c9 100644
--- a/Tests/CoreGraphicsPolyfillTests/PolyfillTests.swift
+++ b/Tests/CoreGraphicsPolyfillTests/PolyfillTests.swift
@@ -84,8 +84,8 @@ final class PolyfillTests: XCTestCase {
         
         XCTAssertEqual(combined.a, 2)
         XCTAssertEqual(combined.d, 3)
-        XCTAssertEqual(combined.tx, 5)
-        XCTAssertEqual(combined.ty, 10)
+        XCTAssertEqual(combined.tx, 10)
+        XCTAssertEqual(combined.ty, 30)
     }
     
     func testTransformFluent() {

From 886701bc7fb8bff06789040a1f383a9a4a515926 Mon Sep 17 00:00:00 2001
From: Dave Aitken <dave.a@goodnotes.com>
Date: Fri, 3 Oct 2025 13:48:34 +0100
Subject: [PATCH 3/3] add test for standard impl of concat operation

---
 Tests/SVGViewTests/CGTests.swift | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
 create mode 100644 Tests/SVGViewTests/CGTests.swift

diff --git a/Tests/SVGViewTests/CGTests.swift b/Tests/SVGViewTests/CGTests.swift
new file mode 100644
index 0000000..41f926c
--- /dev/null
+++ b/Tests/SVGViewTests/CGTests.swift
@@ -0,0 +1,17 @@
+import XCTest
+@testable import SVGView
+
+class CGTests: BaseTestCase {
+
+    func testTransformConcatenation() {
+        let transform1 = CGAffineTransform(translationX: 5, y: 10)
+        let transform2 = CGAffineTransform(scaleX: 2, y: 3)
+        let combined = transform1.concatenating(transform2)
+        
+        XCTAssertEqual(combined.a, 2)
+        XCTAssertEqual(combined.d, 3)
+        XCTAssertEqual(combined.tx, 10)
+        XCTAssertEqual(combined.ty, 30)
+    }
+
+}