From 90cc65066dfa7dc9795c1457cde8ed509a08a4ca Mon Sep 17 00:00:00 2001
From: ICOM725 <ICOM725@gmail.com>
Date: Sat, 5 Sep 2026 19:53:36 +0800
Subject: [PATCH] Fix polygon stroke vertex deduplication

---
 src/gameobjects/shape/StrokePathWebGL.js      |  2 +-
 .../gameobjects/shape/StrokePathWebGL.test.js | 80 +++++++++++++++++++
 2 files changed, 81 insertions(+), 1 deletion(-)
 create mode 100644 tests/gameobjects/shape/StrokePathWebGL.test.js

diff --git a/src/gameobjects/shape/StrokePathWebGL.js b/src/gameobjects/shape/StrokePathWebGL.js
index 3fd93a1f26..fdf128f60f 100644
--- a/src/gameobjects/shape/StrokePathWebGL.js
+++ b/src/gameobjects/shape/StrokePathWebGL.js
@@ -46,7 +46,7 @@ var StrokePathWebGL = function (drawingContext, submitter, matrix, src, alpha, d
         var y = path[i + 1] - dy;
         if (i > 0)
         {
-            if (x === path[i - 2] && y === path[i - 1])
+            if (path[i] === path[i - 2] && path[i + 1] === path[i - 1])
             {
                 // Duplicate point, skip it
                 continue;
diff --git a/tests/gameobjects/shape/StrokePathWebGL.test.js b/tests/gameobjects/shape/StrokePathWebGL.test.js
new file mode 100644
index 0000000000..a33b582281
--- /dev/null
+++ b/tests/gameobjects/shape/StrokePathWebGL.test.js
@@ -0,0 +1,80 @@
+var StrokePathWebGL = require('../../../src/gameobjects/shape/StrokePathWebGL');
+
+describe('StrokePathWebGL', function ()
+{
+    var src;
+    var strokePath;
+
+    beforeEach(function ()
+    {
+        strokePath = { run: vi.fn() };
+
+        src = {
+            pathData: [ 3, 0, 6, 3, 3, 6, 0, 3, 3, 0 ],
+            closePath: true,
+            lineWidth: 2,
+            strokeColor: 0x000000,
+            strokeAlpha: 1,
+            customRenderNodes: {},
+            defaultRenderNodes: { StrokePath: strokePath }
+        };
+    });
+
+    it('preserves every corner and the closing point of a centered diamond', function ()
+    {
+        StrokePathWebGL({}, {}, {}, src, 1, 3, 3);
+
+        expect(strokePath.run.mock.calls[0][2]).toEqual([
+            { x: 0, y: -3, width: 2 },
+            { x: 3, y: 0, width: 2 },
+            { x: 0, y: 3, width: 2 },
+            { x: -3, y: 0, width: 2 },
+            { x: 0, y: -3, width: 2 }
+        ]);
+    });
+
+    it('removes consecutive duplicate vertices with a non-zero display origin', function ()
+    {
+        src.pathData = [ 3, 0, 3, 0, 3, 0, 6, 3, 3, 6, 0, 3, 3, 0 ];
+
+        StrokePathWebGL({}, {}, {}, src, 1, 3, 3);
+
+        expect(strokePath.run.mock.calls[0][2]).toEqual([
+            { x: 0, y: -3, width: 2 },
+            { x: 3, y: 0, width: 2 },
+            { x: 0, y: 3, width: 2 },
+            { x: -3, y: 0, width: 2 },
+            { x: 0, y: -3, width: 2 }
+        ]);
+    });
+
+    it('still removes consecutive duplicate vertices with a zero display origin', function ()
+    {
+        src.pathData = [ 3, 0, 3, 0, 3, 0, 6, 3, 3, 6, 0, 3, 3, 0 ];
+
+        StrokePathWebGL({}, {}, {}, src, 1, 0, 0);
+
+        expect(strokePath.run.mock.calls[0][2]).toEqual([
+            { x: 3, y: 0, width: 2 },
+            { x: 6, y: 3, width: 2 },
+            { x: 3, y: 6, width: 2 },
+            { x: 0, y: 3, width: 2 },
+            { x: 3, y: 0, width: 2 }
+        ]);
+    });
+
+    it('preserves distinct vertices while omitting the closing point of an open path', function ()
+    {
+        src.closePath = false;
+
+        StrokePathWebGL({}, {}, {}, src, 1, 3, 3);
+
+        expect(strokePath.run.mock.calls[0][2]).toEqual([
+            { x: 0, y: -3, width: 2 },
+            { x: 3, y: 0, width: 2 },
+            { x: 0, y: 3, width: 2 },
+            { x: -3, y: 0, width: 2 }
+        ]);
+        expect(strokePath.run.mock.calls[0][4]).toBe(true);
+    });
+});