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