`fullScreen(P2D, SPAN)` does not span across multiple displays on macOS

Most appropriate sub-area of Processing 4?

Core/Environment/Rendering

Processing version

4.5.2

Operating system

MacOS 15.6.1 (24G90)

Bug description

The reference for fullScreen() states that using SPAN should run the sketch “at the full dimensions across all of the attached screens”.

When running a sketch with fullScreen(P2D, SPAN) on my setup, the sketch only appears on the main display.

Hardware setup: 3 external displays connected through an iVANKY FusionDock Max 1 (Note: this is not using DisplayLink):

• DisplayPort → Dell U2720Q (3840×2160)
• HDMI → Dell U2419H (1920×1080)
• HDMI → Dell U2419H (1920×1080)

Steps to reproduce this

1. Connect multiple displays to a macOS machine.
2. Run the sketch below in Processing 4.5.2 (macOS)
3. Observe whether the rendered output spans continuously across all displays.

snippet

// If more than one screen is attached to the computer, run the 
// code at the full dimensions across all of the attached screens

int x = 0;

void setup() {
  fullScreen(P2D, SPAN);
  background(0);
  noStroke();
  fill(102);
}

void draw() {
  rect(x, height*0.2, 1, height*0.6); 
  x = x + 2;
}

Additional context

This may be related to #1426

Would you like to work on the issue?

No, I’m just reporting the issue

Start by running the provided Processing sketch with multiple displays on macOS and compare the behavior with the fullScreen() reference. Review the related issue #1426 for context; done means P2D with SPAN renders continuously across all attached displays rather than only the main display.