String tx="Jarek Rossignac", xt;
void setup() {
  size(600, 400);  
  PFont font = loadFont("Courier-14.vlw"); textFont(font, 14); xt=invert(tx);
  }
 
void draw() {background(200); 
   scribe("1 - copy text into the clipboard",0); 
   scribe("2 - click in this window",1); 
   scribe("3 - paste the inverted clipboard",2); 
   scribe(tx+" | "+xt,4);}

void mousePressed()  {tx=getClipboard(); xt=invert(tx); setClipboard(xt);};
 
void scribe(String S, int i) {fill(0); text(S,20,20+i*20); noFill();}
String invert(String te) {String et=""; for (int i=te.length()-1; i>=0; i--) et=et+te.charAt(i); return et;}

import java.awt.Toolkit;
import java.awt.datatransfer.*;
public static String getClipboard() {   // returns content of clipboard (if it contains text) or null
       Transferable t = Toolkit.getDefaultToolkit().getSystemClipboard().getContents(null);
       try {if (t != null && t.isDataFlavorSupported(DataFlavor.stringFlavor)) {
               String text = (String)t.getTransferData(DataFlavor.stringFlavor);
               return text; }} 
       catch (UnsupportedFlavorException e) { } catch (IOException e) { }
       return null;
       }
public static void setClipboard(String str) { // This method writes a string to the system clipboard.
       StringSelection ss = new StringSelection(str);
       Toolkit.getDefaultToolkit().getSystemClipboard().setContents(ss, null);
       }
public void test() {System.out.println(getClipboard()); setClipboard("hello world"); }