From cc12bbe5991ab6f335e429887f6ad5a2ad61da22 Mon Sep 17 00:00:00 2001
From: Kyue <164024549+Gooh456@users.noreply.github.com>
Date: Fri, 24 Jul 2026 17:33:45 +0100
Subject: [PATCH] fix(image): reject non-positive duration in saveGif()

saveGif('name', 0) or a negative duration captures zero frames, then
_generateGlobalPalette does `new Uint8Array(frames.length * frames[0].length)`
with frames empty, so frames[0] is undefined and it throws
"Cannot read properties of undefined (reading 'length')".

Every other bad param in saveGif already throws up front, so guard duration
the same way and throw a RangeError before recording starts.

Fixes #8710

Signed-off-by: Kyue <164024549+Gooh456@users.noreply.github.com>
---
 src/image/loading_displaying.js | 5 +++++
 test/unit/image/downloading.js  | 5 +++++
 2 files changed, 10 insertions(+)

diff --git a/src/image/loading_displaying.js b/src/image/loading_displaying.js
index 3d23cc4c0b..fd3ba0aa30 100644
--- a/src/image/loading_displaying.js
+++ b/src/image/loading_displaying.js
@@ -265,6 +265,11 @@ function loadingDisplaying(p5, fn){
     if (typeof duration !== 'number') {
       throw TypeError('Duration parameter must be a number');
     }
+    // a non-positive duration captures zero frames, which later crashes
+    // in palette generation (frames[0] is undefined). reject early.
+    if (duration <= 0) {
+      throw RangeError('Duration parameter must be greater than 0');
+    }
 
     // extract variables for more comfortable use
     const delay = (options && options.delay) || 0;  // in seconds
diff --git a/test/unit/image/downloading.js b/test/unit/image/downloading.js
index 3d37d979e3..edc025d1a9 100644
--- a/test/unit/image/downloading.js
+++ b/test/unit/image/downloading.js
@@ -177,6 +177,11 @@ suite('Downloading', () => {
       assert.typeOf(mockP5Prototype.saveGif, 'function');
     });
 
+    test('should reject a non-positive duration', async () => {
+      await expect(mockP5Prototype.saveGif('myGif', 0)).rejects.toThrow();
+      await expect(mockP5Prototype.saveGif('myGif', -3)).rejects.toThrow();
+    });
+
     // TODO: this implementation need refactoring
     test.todo('should not throw an error', async () => {
       await mockP5Prototype.saveGif('myGif', 3);