This is achieved by supplying isModal:true In the configuration object. As you can see, the entire browser window has been 'overlayed' by a transparent background. Because this sits 'on top' of what is there, no user interaction is possible except for the new dialogue.

This simulates the standard desktop Modal dialogue -- or Alert dialogues etc. from JavaScript.

When you close the window, the background will be removed, and you can access the underlying 'controls' again.