hello,

in my understanding, you can use a principle called states.

The program always has a state it is in.

So your

• 1st state is wait for user input
• 2nd is user clicks somewhere on a worldmap (on homescreen), he should see another window that shows search results
• 3rd: user clicks on a particular button on the screen, he should be able to see a completely different window with its own controls

what you do is to have

1. swich(state) {
2. case stateWaitForuserInput:
3. showMainScreen();
4. break;
5. case ............................
6. .........................
7. break;
8. .................
9. ................
   
10. default:
11. println ("Error 2318: unknown state in draw()"); // error in programming, quit
    
12. exit();
13. break;
14. } // switch
    

in draw() but also in keyPressed and in mousePressed. So you can allow certain keys in each state or certain mouse actions.


Changing the states
You then have to have places where you say (when the user clicks a certain place)

1. state = stateShowSearchResults;

and when he goes back to the main window
say

1. state=stateWaitForuserInput;

Also when you enter a new state you might want to delete your list of screen buttons and fill it with new buttons (for the other screen). When you re-enter main-screen, restore the list of screen buttons.


Preparations
So before setup() have

1. // we give the different states names
   
2. final int stateWaitForuserInput    =0;  // const: naming the states
   
3. final int stateShowSearchResults=1;  // const:
4. final int stateState3                    =2;  // const: better name needed
   
5. int state=stateWaitForuserInput;  // current state
   

In my experience this approach is very clear and stable.

See an example here:
https://forum.processing.org/topic/i-need-create-menu#25080000002245819

Greetings, Chrisir