From c23d1c0febae41bb0f3da99c47aa259f97dc17ff Mon Sep 17 00:00:00 2001
From: Dave Pagurek <davepagurek@gmail.com>
Date: Wed, 13 May 2026 09:37:31 -0400
Subject: [PATCH] Don't use push(...arr) in GeometryBuilder for long vertex
 arrays

---
 src/webgl/GeometryBuilder.js     | 24 +++++++++++++++---------
 test/unit/webgl/p5.RendererGL.js | 17 +++++++++++++++++
 2 files changed, 32 insertions(+), 9 deletions(-)

diff --git a/src/webgl/GeometryBuilder.js b/src/webgl/GeometryBuilder.js
index b59548bf67..777feb838e 100644
--- a/src/webgl/GeometryBuilder.js
+++ b/src/webgl/GeometryBuilder.js
@@ -64,11 +64,15 @@ class GeometryBuilder {
     }
 
     let startIdx = this.geometry.vertices.length;
-    this.geometry.vertices.push(...this.transformVertices(input.vertices));
-    this.geometry.vertexNormals.push(
-      ...this.transformNormals(input.vertexNormals)
-    );
-    this.geometry.uvs.push(...input.uvs);
+    for (const v of this.transformVertices(input.vertices)) {
+      this.geometry.vertices.push(v);
+    }
+    for (const vn of this.transformNormals(input.vertexNormals)) {
+      this.geometry.vertexNormals.push(vn);
+    }
+    for (const val of input.uvs) {
+      this.geometry.uvs.push(val);
+    }
 
     const inputUserVertexProps = input.userVertexProperties;
     const builtUserVertexProps = this.geometry.userVertexProperties;
@@ -103,15 +107,17 @@ class GeometryBuilder {
       );
     }
     if (this.renderer.states.strokeColor) {
-      this.geometry.edges.push(
-        ...input.edges.map(edge => edge.map(idx => idx + startIdx))
-      );
+      for (const edge of input.edges.map(edge => edge.map(idx => idx + startIdx))) {
+        this.geometry.edges.push(edge);
+      }
     }
     const vertexColors = [...input.vertexColors];
     while (vertexColors.length < input.vertices.length * 4) {
       vertexColors.push(...this.renderer.states.curFillColor);
     }
-    this.geometry.vertexColors.push(...vertexColors);
+    for (const c of vertexColors) {
+      this.geometry.vertexColors.push(c);
+    }
   }
 
   /**
diff --git a/test/unit/webgl/p5.RendererGL.js b/test/unit/webgl/p5.RendererGL.js
index 1b6b59c78f..aaa229bcec 100644
--- a/test/unit/webgl/p5.RendererGL.js
+++ b/test/unit/webgl/p5.RendererGL.js
@@ -3089,6 +3089,23 @@ suite('p5.RendererGL', function() {
       myp5.model(geom);
       expect(myp5.get(5, 5)).toEqual([255, 0, 0, 255]);
     });
+    test('does not throw with a large number of vertices', function() {
+      myp5.createCanvas(10, 10, myp5.WEBGL);
+      // Enough triangles to exceed the ~65k argument limit of Function.prototype.apply,
+      // which would cause a stack overflow if vertices were spread into push() calls.
+      const numTriangles = 30000;
+      expect(() => {
+        myp5.buildGeometry(() => {
+          myp5.beginShape(myp5.TRIANGLES);
+          for (let i = 0; i < numTriangles; i++) {
+            myp5.vertex(0, 0, 0);
+            myp5.vertex(1, 0, 0);
+            myp5.vertex(0, 1, 0);
+          }
+          myp5.endShape();
+        });
+      }).not.toThrow();
+    });
   });
 
   suite('fontWidth', function() {