NPE when calling background or setunder P3D renderer

[kfrajer]

Forum post here which I will copy the relevant pieces next:

From the trace call, I can see the problem is the background() function call in OPENGL mode. I am able to reproduce the problem with the following MCVE (plz ensure image is in the data folder):

import android.os.Environment;
import android.os.Build ;
import android.app.Activity;
import android.content.Context;
 
PImage back; 
 
void setup(){
  size(displayWidth, displayHeight, P3D);
  back = loadImage("bg.jpg");
}
 
void draw(){ 
   background(back);                      <----NPE!
   //set(0,0,back);                           <----NPE!
   //image(back,0,0,width,height);  <--It works 
}

Notice that when using P3D:

• Either background() or set() throws an NPE and App crashes
• It works normally if one uses image() instead,

Using the default renderer, you can use either background/set/image and you won't have any problem. I tested this using Win10, AM 4.0.1 and P3.3.6 on SG8 Nougat.

Back trace output next based on background():

//FATAL EXCEPTION: GLThread 181069
//Process: processing.test.sketch_180219b, PID: 7447
//java.lang.NullPointerException: src == null
// at java.lang.System.arraycopy(Native Method)
// at processing.opengl.PGraphicsOpenGL.setImpl(Unknown Source)
// at processing.core.PImage.set(Unknown Source)
// at processing.opengl.PGraphicsOpenGL.backgroundImpl(Unknown Source)
// at processing.core.PGraphics.background(Unknown Source)
// at processing.core.PApplet.background(Unknown Source)
// at processing.test.sketch_180219b.sketch_180219b.draw(sketch_180219b.java:123)
// at processing.core.PApplet.handleDraw(Unknown Source)
// at processing.opengl.PSurfaceGLES$RendererGLES.onDrawFrame(Unknown Source)
// at android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1562)
// at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1262)

Back trace output next based on set():

//FATAL EXCEPTION: GLThread 183761
//Process: processing.test.sketch_180219b, PID: 3877
//java.lang.NullPointerException: src == null
// at java.lang.System.arraycopy(Native Method)
// at processing.opengl.PGraphicsOpenGL.setImpl(Unknown Source)
// at processing.core.PImage.set(Unknown Source)
// at processing.core.PApplet.set(Unknown Source)
// at processing.test.sketch_180219b.sketch_180219b.draw(sketch_180219b.java:132)
// at processing.core.PApplet.handleDraw(Unknown Source)
// at processing.opengl.PSurfaceGLES$RendererGLES.onDrawFrame(Unknown Source)
// at android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1562)
// at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1262)

These lines are of interest based on the trace:
https://github.com/processing/processing-android/blob/master/core/src/processing/opengl/PGraphicsOpenGL.java#L5798
https://github.com/processing/processing-android/blob/master/core/src/processing/core/PApplet.java#L9670
https://github.com/processing/processing-android/blob/master/core/src/processing/opengl/PGraphicsOpenGL.java#L5787
https://github.com/processing/processing-android/blob/master/core/src/processing/opengl/PGraphicsOpenGL.java#L5474

Kf

[kfrajer]

Fix summary: The reason of this error is bc of the implementation of the set() function, which is called by by Background(...). Looking at the error code and after inspecting the code, the fix boils down to adding the following line to setImpl(...) function in PGraphicsOpenGL.java:

if(sourceImage.pixels==null) sourceImage.loadPixels(); // TAG: CHANGE,FIX

I provide a test code below, which it is not needed but form completeness. It has a setup, draw and clones of the set and setImpl function (labeled setCM and setImplCM). You just need to jump directly to the line tagged TAG: CHANGE, FIX. I will be submitting a pull request shortly. If I don't, you can easily upload this change in the main repo.

Kf

import android.app.Activity;
import android.content.Context;
import android.widget.FrameLayout;
//import android.app.Fragment;

import android.os.Environment;
import android.graphics.Color;
import android.widget.Toast;
import android.os.Looper;
import android.view.WindowManager;
import android.os.Bundle;
import android.view.ViewParent;
import android.view.ViewGroup;
import android.view.View;
import android.widget.RelativeLayout;
import android.view.LayoutInflater;
import android.R.string;


//===========================================================================
// FINAL FIELDS:


//===========================================================================
// GLOBAL VARIABLES:

Activity act;
Context mC;
PImage back;

//===========================================================================
// PROCESSING DEFAULT FUNCTIONS:

void setup() {
  //size(displayWidth, displayHeight, P3D);
  fullScreen(P2D);
  orientation(PORTRAIT);
  //orientation(LANDSCAPE;)


  act = this.getActivity();
  Looper.prepare();

  textAlign(CENTER, CENTER);
  rectMode(CENTER);

  fill(255);
  strokeWeight(2);
  textSize(32);


  back = loadImage("pic42.jpg");
  back.resize(width,height);
}

void draw() {
  
  println("back.pixelDensity: "+back.pixelDensity);
  setCM(0,0,back); 
  
  //background(back);                     //<----NPE!
  //set(0,0,back);                           <----NPE!
  //image(back,0,0,width,height);  <--It works
}


public void setCM(int x, int y, PImage img) {
    if (img.format == ALPHA) {
      // set() doesn't really make sense for an ALPHA image, since it
      // directly replaces pixels and does no blending.
      throw new IllegalArgumentException("set() not available for ALPHA images");
    }

    int sx = 0;
    int sy = 0;
    int sw = img.width;
    int sh = img.height;

    if (x < 0) {  // off left edge
      sx -= x;
      sw += x;
      x = 0;
    }
    if (y < 0) {  // off top edge
      sy -= y;
      sh += y;
      y = 0;
    }
    if (x + sw > width) {  // off right edge
      sw = width - x;
    }
    if (y + sh > height) {  // off bottom edge
      sh = height - y;
    }

    // this could be nonexistent
    if ((sw <= 0) || (sh <= 0)) return;

    setImplCM(img, sx, sy, sw, sh, x, y);
  }
  
  protected void setImplCM(PImage sourceImage,
                         int sourceX, int sourceY,
                         int sourceWidth, int sourceHeight,
                         int targetX, int targetY) {
    
                           //updatePixelSize();  INSTEAD use next two lines  TAG: CHANGE
    println("W=",width,pixelWidth);
    println("H=",height,pixelHeight);   
    

    // Copies the pixels
    loadPixels();
    if(sourceImage.pixels==null) sourceImage.loadPixels();  // TAG: CHANGE,FIX
    
    int sourceOffset = sourceY * sourceImage.pixelWidth + sourceX;
    int targetOffset = targetY * pixelWidth + targetX;
    for (int y = sourceY; y < sourceY + sourceHeight; y++) {
      System.arraycopy(sourceImage.pixels, sourceOffset, pixels, targetOffset, sourceWidth);
      sourceOffset += sourceImage.pixelWidth;
      targetOffset += pixelWidth;
    }

    // Draws the texture, copy() is very efficient because it simply renders
    // the texture cache of sourceImage using OpenGL.
    copy(sourceImage,
         sourceX, sourceY, sourceWidth, sourceHeight,
         targetX, targetY, sourceWidth, sourceHeight);
  }