The P2D and P3D renderers in Processing version 2 now use OpenGL and this is causing some problems for G4P when creating GWindow objects with these renderers.

At the momemnt I recommend that you only use the JAVA2D renderer for additional windows. The code below works with 2.0b8 so will probably works with 2.0b9 (I have not installed 2.0b9 yet).

I will be investigating the problem of GWindow using the P2D and P3D renderers but I don'y know when or whether I will find a solution.

1. import g4p_controls.*;
2. GWindow Einstellungen;
3. 
   
4. public void setup() {
5.   size(400, 400, P2D);
6.   Einstellungen = new GWindow(this, "Einstellungen", 0, 0, 320, 550, false, JAVA2D);
7.   Einstellungen.setActionOnClose(GWindow.CLOSE_WINDOW);
8.   Einstellungen.setResizable(false);
9.   Einstellungen.addDrawHandler(this, "win_draw1");
10. }
11. 
    
12. public void win_draw1(GWinApplet winapplet, GWinData windata) {
13.   winapplet.background(0, 128, 0);
14. }
15. 
    
16. public void draw() {
17. }

Thank you for replying that fast, but closing the Window on close still doesn't work... and I don't know how to check wheter the window is open or it is not. 

I have now tested the above code with 2.0b9 and it works.

In the code below I have added a button which when clicked will close the window. The window can also be closed by clicking on the Close icon on the window title bar.

The code inside the draw method shows how you can find out whether a GWindow object is open or closed.

Please note - this only works with GWindow objects created inside your sketch (provided they use the JAVA2D renderer). If you close the main sketch window it will exit the application the same as any other application.

1. import g4p_controls.*;
2. 
   
3. GWindow Einstellungen;
4. GButton btnCloseWindow;
5. ArrayList<GWindow> windowsList;
6. 
   
7. public void setup() {
8.   size(400, 400, P2D);
9.   btnCloseWindow = new GButton(this, 10, 10, 100, 20, "Close Window");
10.   Einstellungen = new GWindow(this, "Einstellungen", 0, 0, 320, 550, false, JAVA2D);
11.   Einstellungen.setActionOnClose(GWindow.CLOSE_WINDOW);
12.   Einstellungen.setResizable(false);
13.   Einstellungen.addDrawHandler(this, "win_draw1");
14. }
15. public void win_draw1(GWinApplet winapplet, GWinData windata) {
16.   winapplet.background(0, 128, 0);
17. }
18. 
    
19. public void draw() {
20.   background(255, 255, 2300);
21.   fill(0);
22.   windowsList = G4P.getOpenWindowsAsList(windowsList);
23.   if (windowsList.contains(Einstellungen))
24.     text("Window OPEN", 20, 100);
25.   else
26.     text("Window CLOSED", 20, 120);
27. }
28. 
    
29. public void handleButtonEvents(GButton button, GEvent event) {
30.   if (button == btnCloseWindow && event == GEvent.CLICKED) {
31.     Einstellungen.close();
32.   }
33. }