When making a window with a GUI how do you get the dimensions of a full-screen window

So I want to make a full-screen window and draw to it and get other windows to pop up. like it says in the examples. To draw to my main window technically I don’t know it’s dimensions. I have used all of the methods that I could find including ofgetscreenwidth and ofgetscreenheight I have not used the size methods, because I do not know how to separate the width and height.

You can define variables in ofApp to store the height and width, and then in the body of ofApp::windowResized(int w, int h), fill them in and do any other adjustments you want.

DisplayHeight = h;
DisplayWidth = w;