NullPointerException on Dynamic Window Resize in Processing

[famousgrouse44]

Most appropriate sub-area of Processing 4?

Core/Environment/Rendering

Processing version

4.4.4

Operating system

Windows 10

Steps to reproduce this

1. Description :
When dynamically resizing a Processing sketch window (via surface.setSize(w, h) or by enabling surface.setResizable(true)), a NullPointerException may occur in Component$BltBufferStrategy.revalidate(...), due to an internal backBuffers[] array being null.

This happens during the rendering phase, likely due to an invalidated or uninitialized BufferStrategy after the resize.

2. Example Stack Trace :

java.lang.NullPointerException: Cannot invoke "java.awt.image.VolatileImage.validate(java.awt.GraphicsConfiguration)" because "this.backBuffers[...]" is null
    at java.desktop/java.awt.Component$BltBufferStrategy.revalidate(Component.java:4552)
    at java.desktop/java.awt.Component$BltBufferStrategy.getDrawGraphics(Component.java:4449)
    at processing.awt.PSurfaceAWT.render(PSurfaceAWT.java:242)
    at processing.awt.PSurfaceAWT$9.callDraw(PSurfaceAWT.java:1389)
    at processing.core.PSurfaceNone$AnimationThread.run(PSurfaceNone.java:356)

3. Expected Behavior :
When resizing the window, either manually (with setResizable(true)) or programmatically (via surface.setSize(w, h)), the sketch should continue rendering smoothly without crashing or throwing an exception.

snippet

// Paste your code below :)

void setup() {
  size(600, 400);
  surface.setResizable(true);
}

void draw() {
  background(200);
}

Additional context

Discovered Workaround :

Calling surface.setVisible(true) immediately after resizing prevents the crash :

surface.setSize(w, h);
surface.setVisible(true);               // Prevents the NPE

Would you like to work on the issue?

No

[SableRaf]

Hi @famousgrouse44 and thanks for reporting and investigating this issue. Resizeable windows are a relatively new feature in Processing and they could definitely use a little more love.

I noticed something similar but with a different error message here.

Screen.Recording.2025-04-01.at.21.31.53.mov

[DanielMyers993]

It strangely broke again after I put this rect(0,0,width/2,height/2) same error. but then it worked sometimes but not all the times?

[tudasamenc]

Hi, if anyone hasn't worked on this, I'd like to attempt to fix it

[SableRaf]

Hi, if anyone hasn't worked on this, I'd like to attempt to fix it

Hi @tudasamenc and thanks for your help!

Before assigning the issue, I'd recommend setting up the project locally and verifying that you can build it. You’ll find instructions in the BUILD.md file.

Also, just a heads-up that this issue may be related to #1003, which @duskvirkus has been investigating. You might want to check their notes there before starting.

Let us know once you’ve got the build running or if you need any guidance.

[tudasamenc]

Hi, if anyone hasn't worked on this, I'd like to attempt to fix it

Hi @tudasamenc and thanks for your help!

Before assigning the issue, I'd recommend setting up the project locally and verifying that you can build it. You’ll find instructions in the BUILD.md file.

Also, just a heads-up that this issue may be related to #1003, which @duskvirkus has been investigating. You might want to check their notes there before starting.

Let us know once you’ve got the build running or if you need any guidance.

Hi! I just set up the environment. I have it up and running, if there aren't any issues I'll start working on it, thanks!