I am currently writing a library to provide Utility to others writing processing libraries. A core feature is the detection of all PApplet instances.
After 4 months of development I finally found a possibility that should work for both Processing 3 and 4 I would like however assert that it really works with Processing 4.
(This is the according thread in the forum: Get the current instance of PApplet from a library - Processing / Coding Questions - Processing Foundation)
This sketch utilizes a .java tab:
PAppletFinder.java
import processing.awt.*;
import processing.opengl.*;
import processing.core.*;
import javax.swing.*;
import java.awt.*;
import java.util.*;
import java.lang.reflect.*;
import sun.misc.*;
/**This class finds the active PApplet (Processing program)
@author NumericPrime*/
public class PAppletFinder {
/**Unsafe instance used*/
public static Unsafe unsafe=null;
/**Unsafe Field offset*/
public static long fieldIndex=0;
/**Target field of the thread*/
public static Field threadTargField=null;
/**Here the three Fields unsafe,fieldIndex, threadTargField are initalized*/
static {
try {
Field f2=Unsafe.class.getDeclaredField("theUnsafe");
f2.setAccessible(true);
unsafe=(Unsafe) f2.get(null);
//System.out.println("Unsafe instance: "+unsafe.toString());
threadTargField=Thread.class.getDeclaredField("target");
fieldIndex=unsafe.objectFieldOffset(threadTargField);
}
catch(Exception e) {
e.printStackTrace();
}
}
/**Getter-Method used to detect all PApplets. If the detection hasn't run yet this method will run it.
@param refresh if true: redetects all PApplets
@return all detected PApplets*/
public static PApplet[] getPApplets(boolean refresh) {
int allfpSize=0;
if (refresh) allFoundPapplets.clear();
if ((allfpSize=allFoundPapplets.size())==0) findAll();
return allFoundPapplets.toArray(new PApplet[allfpSize]);
}
/**All results will be saved here*/
public static java.util.List<PApplet> allFoundPapplets=new LinkedList<PApplet>();
/**This class takes the contents of the window and pieces together the PApplet
* @return PApplet of the current sketch.
* @param c contents of the Processing window (must be a SmoothCanvas)*/
public static void get(Component c) {
//System.out.println("Processing Window content");
PSurfaceAWT.SmoothCanvas sc=(PSurfaceAWT.SmoothCanvas) c;
try {
//gets the PSurface for the PApplet
PSurfaceAWT psa=(PSurfaceAWT) get(sc, "this$0", sc.getClass());
//gets the PApplet
PApplet prg=(PApplet) get((PSurfaceNone)psa, "sketch", PSurfaceNone.class);
allFoundPapplets.add(prg);
}
catch(Exception e) {
//System.err.println("Something went wrong");
e.printStackTrace();
}
}
/**This method tries to detect all PApplet used*/
public static void findAll() {
findFromWindow();
fromThreads();
//System.out.println("Detection done");
}
/**This looks out for processing-windows and gives the contents of the right one to the get method*/
public static void findFromWindow() {
//System.out.println("Searching Windows for instances");
JFrame mainWindow=null;
java.awt.Window win[]=java.awt.Window.getWindows();
for (int i=0; i<win.length; i++) if (win[i] instanceof JFrame) {
mainWindow=(JFrame) win[i];
Component c=mainWindow.getContentPane().getComponents()[0];
if (c instanceof PSurfaceAWT.SmoothCanvas) get(c);
}
}
/**This is used to get the value of fields
* @return Object value of a field
* @param j the Object from which the value is taken
* @param target name of the field
* @param ref class the field is taken from*/
public static Object get(Object j, String target, Class<?> ref) {
try {
Field f=ref.getDeclaredField(target);
f.setAccessible(true);
return f.get(j);
}
catch (Exception e) {
e.printStackTrace();
}
return null;
}
/** When using P2D or P3D everything is built differently however there is a weakness to be found in
* PSurfaceJOGL as it dispatches a Thread using an annonymous inner class as Runnable*/
public static void fromThreads() {
//System.out.println("Searching Threads for instances");
//This fetches all threads
Set<Thread> threadSet=Thread.getAllStackTraces().keySet();
//It iterates upon the threads to find ones dispatched by PSurfaceJOGL
for (Thread th : threadSet) {
iteration:
{
try {
//Field f=th.getClass().getDeclaredField("target");
//f.setAccessible(true);
Object currinstance=null;
//Here Unsafe is used to breach encapsulation of java.lang
currinstance=unsafe.getObject(th, fieldIndex);
if (!currinstance.getClass().toString().contains("PSurfaceJOGL$")) break iteration;
//System.out.println("Weak spot found! "+th.getName());
//gets the PSurfaceJOGL
currinstance=getEnclosingInstance(currinstance);
//gets the PApplet
Field f=PSurfaceJOGL.class.getDeclaredField("sketch");
f.setAccessible(true);
allFoundPapplets.add((PApplet) (currinstance=f.get(currinstance)));
//System.out.println("Detection successful");
}
catch(Exception e)
{
catchBlock:
{
if (e instanceof NoSuchFieldException||e instanceof NullPointerException) {
//System.err.println("target not found "+th.getName());
//A NullPointerException may occur
break catchBlock;
}
//System.err.println("Something went wrong!");
e.printStackTrace();
}
}
}
}
}
//This will try to get the enclosing instance of an object (this can also be a lambda)
public static Object getEnclosingInstance(Object o) {
//This code will work for Processing 3 (uses annonymous inner classes)
try {
Class<?> classused=o.getClass();
Field this0=classused.getDeclaredField("this$0");
this0.setAccessible(true);
return this0.get(o);
}
catch(Exception e) {
//System.err.println("Can't find enclosing instance of Object, trying to use Lambdas... (To be expected with Processing 4)");
}
//This code should work for Processing 4 (lambdas are used instead of inner classes, Lambdas use arg$1 instead this$0)
try {
Class<?> classused=o.getClass();
Field this0=classused.getDeclaredField("arg$1");
this0.setAccessible(true);
return this0.get(o);
}
catch(Exception e) {
//System.err.println("Detection Failed!");
}
return null;
}
}
This is the code of the main sketch:
MainSketch.pde
void setup() {
size(300,300,JAVA2D);
println(this,PAppletFinder.getPApplets(false)[0]);
}
void draw() {
}
This should print something like:
MainSketch@64638317 [MainSketch@64638317]
If it doesn’t please wirte the contents of the console, so I can try to debug it.
Please also test this code with P3D and P2D.