If you have used a moderately complex application there are chances that you have interacted with what is called a “modal” dialog. A modal dialog is a dialog that requires you to close/address it before you can continue interacting with the main application window. This can be implemented by the application in a straightforward manner but compositor didn’t know if a dialog was modal or not.
This is a companion discussion topic for the original entry at https://blog.david-redondo.de/kde/wayland/qt/2024/04/04/xdg-dialog.html