Display count needs to be implemented for non-AWT

AlexRussell · August 21, 2026, 9:45am

Since I updated to Processing 4.5.6 (on Win 11), every sketch runs okay, but gets the error message:
“display count needs to be implemented for non-AWT
AWT disabled, displayWidth/displayHeight will be 0”
Nothing here: fullScreen(P3D) not fullscreening on Windows or on the pages it links to seems to be helping.
I’m using a fixed display window, size(1080, 1080) without P2D or P3D, with pixelDensity(1)
It doesn’t actually seem to be affecting how the code works, but I wouldn’t mind knowing why this is happening and if it is possible to get rid of it.
Any help very gratefully received by a first-time poster. Thank you.

Leo_N · August 28, 2026, 6:08am

I’m experiencing the same issue. I upgraded from 4.5.5 to 4.5.6, and even the simplest code triggers the warning.

I also use secondary window functionality, and the warning appears every time a secondary window is called.

I’ve reverted to 4.5.5 for now because I capture system output to log, and the repeated warnings are flooding my logs.

svan · August 28, 2026, 4:12pm

Take a look at this reference to gain some insight into why this is happening:

github.com/processing/processing4

core/src/processing/core/PApplet.java

main

/* -*- mode: java; c-basic-offset: 2; indent-tabs-mode: nil -*- */

/*
  Part of the Processing project - http://processing.org

  Copyright (c) 2012-22 The Processing Foundation
  Copyright (c) 2004-12 Ben Fry and Casey Reas
  Copyright (c) 2001-04 Massachusetts Institute of Technology

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation, version 2.1.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General
  Public License along with this library; if not, write to the

This file has been truncated. show original

This file contains this code:

 public int displayDensity() {
    if (display != SPAN && (fullScreen || present)) {
      return displayDensity(display);
    }

    int displayCount = 0;
    if (!disableAWT) {
      displayCount = ShimAWT.getDisplayCount();
    } else {
      // https://github.com/processing/processing4/issues/57
      System.err.println("display count needs to be implemented for non-AWT");
    }
    // walk through all displays, use 2 if any display is 2
    for (int i = 0; i < displayCount; i++) {
      if (displayDensity(i+1) == 2) {
        return 2;
      }
    }
    // If nobody's density is 2 then everyone is 1
    return 1;
  }

The error message appears to be thrown because disableAWT is set to true. That occurs here:

        case ARGS_DISABLE_AWT:
            disableAWT = true;
            break;

It apparently was set to true for this reason:

/** Disable AWT so that LWJGL and others can run */
static public final String ARGS_DISABLE_AWT = "--disable-awt";

glv · August 29, 2026, 3:38pm

Hello @AlexRussell,

Try this in a sketch:
println("disableAWT: ", disableAWT); // true for 4.5.6 and false for 4.5.5

This was (below) added to Processing 4.5.6 and it is NOT in 4.5.5:

github.com/processing/processing4

java/src/processing/mode/java/runner/Runner.java

main


      
            // so there's a path for debugging all of this. [fry 230218]
            /*
            if (Platform.isWindows()) {
              // Pass the DPI setting to the app to avoid using the helper app.
              int dpi = Toolkit.getDefaultToolkit().getScreenResolution();
              int uiScale = PApplet.constrain(dpi / 96, 1, 2);
              params.append(PApplet.ARGS_UI_SCALE + "=" + uiScale);
            }
            */
          
            // TODO: excise AWT to make webgpu work properly
            params.append(PApplet.ARGS_DISABLE_AWT);
          
            params.append(build.getSketchClassName());
          }
          // Add command-line arguments to be given to the sketch itself
          if (args != null) {
            params.append(args);
          }
          
          // Pass back the whole list

It now checks the argument at startup and displays the errors unconditionally in 4.5.6 that you see.

Trail of breadcrumbs:

github.com/processing/processing4

core/src/processing/core/PApplet.java

main


      
                  break;
          
                case ARGS_EXTERNAL:
                  external = true;
                  break;
          
                case ARGS_FULL_SCREEN:
                  fullScreen = true;
                  break;
          
                case ARGS_DISABLE_AWT:
                  disableAWT = true;
                  break;
          
                default:
                  name = args[argIndex];
                  break label;  // because of break, argIndex won't increment again
              }
            }
            argIndex++;
          }

github.com/processing/processing4

core/src/processing/core/PApplet.java

main


      
              System.err.println("  " + method + "(" + argList.join(", ") + ");");
              System.err.println("}");
            }
            throw new IllegalStateException(method + "() cannot be used here, see " + url);
          }
          
          
          void handleSettings() {
            insideSettings = true;
          
            if (!disableAWT) {
              displayWidth = ShimAWT.getDisplayWidth();
              displayHeight = ShimAWT.getDisplayHeight();
            } else {
              // https://github.com/processing/processing4/issues/57
              System.err.println("AWT disabled, displayWidth/displayHeight will be 0");
            }
          
            // Here's where size(), fullScreen(), smooth(N) and noSmooth() might
            // be called, conjuring up the demons of various rendering configurations.
            settings();

github.com/processing/processing4

core/src/processing/core/PApplet.java

main


      
          * @webBrief Returns "2" if the screen is high-density and "1" if not
          * @see PApplet#pixelDensity(int)
          * @see PApplet#size(int,int)
          */
          public int displayDensity() {
            if (display != SPAN && (fullScreen || present)) {
              return displayDensity(display);
            }
          
            int displayCount = 0;
            if (!disableAWT) {
              displayCount = ShimAWT.getDisplayCount();
            } else {
              // https://github.com/processing/processing4/issues/57
              System.err.println("display count needs to be implemented for non-AWT");
            }
            // walk through all displays, use 2 if any display is 2
            for (int i = 0; i < displayCount; i++) {
              if (displayDensity(i+1) == 2) {
                return 2;
              }

You can also make a custom version of Processing!

processing4/BUILD.md at main · processing/processing4 · GitHub

Note:
I have yet to test out the above in a custom build.
Migrating to a new PC and have other priorities.
I will follow up once I do this… not anytime soon.

:)

sableraph · August 31, 2026, 1:40pm

Thanks for looking into this. I reported this bug in the issue below back in July, and just added a link to this conversation. Feel free to share your findings in the replies and/or suggest/contribute a fix.

github.com/processing/processing4

Display detection fails in Processing 4.5.6 on macOS + pixelDensity()

opened 12:42PM - 20 Jul 26 UTC

SableRaf

bug

### Most appropriate sub-area of Processing 4? Core/Environment/Rendering ### …Processing version 4.5.6 ### Operating system macOS Tahoe 26.5.2 (25F84) ### Bug description Running an empty sketch in Processing 4.5.6 produces the following warnings: ``` display count needs to be implemented for non-AWT AWT disabled, displayWidth/displayHeight will be 0 ``` Additionally, calling `pixelDensity(2)` produces this error: ``` pixelDensity(2) is not available for this display ``` Processing should detect the display dimensions and use `pixelDensity(2)` by default on the built-in Retina display. Regression for: * https://github.com/processing/processing4/pull/1226 * https://github.com/processing/processing4/pull/1038 ### Steps to reproduce this 1. Install Processing 4.5.6 on macOS. 2. Open Processing and create a new sketch. 3. Run the sketch below. 4. Observe the display-count and `displayWidth`/`displayHeight` warnings in the console. 5. Uncomment `pixelDensity(2)`. 6. Run the sketch again. 7. Observe the `pixelDensity(2) is not available for this display` error. ### snippet ```processing void setup(){ size(640,400); //pixelDensity(2); } void draw(){ line(10,10,630,390); } ``` ### Additional context <img width="1118" height="717" alt="Image" src="https://github.com/user-attachments/assets/76fb1896-cab4-4f41-811d-d05761e5874c" /> ### Would you like to work on the issue? No, I’m just reporting the issue

AlexRussell · August 31, 2026, 4:18pm

Thanks everyone for your help with this. I’ve added a comment to the issue @sableraph has raised on GitHub noting that the issue is on PCs running Win 11 as well as Macs. I wish I could code well enough to help fix this!

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Display count needs to be implemented for non-AWT

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