The desired behavior can be achieved with some custom coding that depends on the HTML markup inside the Window. You can use the focus
events of suitable elements on the page, as well as the document's activeElement
The keyCode of the TAB key is 9.
Basically, you need to detect when the focus is moved to a form field or hyperlink outside the Window popup and get it back inside the popup.
There are third-party popup widgets, which provide "true" modality out-of-the-box and access to elements outside the popup is disabled, however, in some scenarios such behavior is too intrusive and has undesired side effects.
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