[simcop2387]

The application side of it is more for things like the multi-window setup of things like GIMP so that windows that are "docked" next to each other will stay that way past restarts. That's one of the reasons that the newer proposals are doing things with relative positioning between a zone or main window rather than allowing applications to place themselves randomly on whatever monitor or space that they want, interrupting whatever workflow is going on (which actually allows for security issues, i.e. a window pretending to be a password prompt putting itself on top of a browser or something to confuse the user). This also allows for new windows from the application to request that they're positioned next to any others so that related things stay together. This also apparently helps in a few cases where a single "application" to the user is actually multiple separate programs that get run by a main interface. Not as common in new software today but it used to be one of the ways that a lot of older software worked and there's still a decent amount out there apparently that are maintained that way.

Keep in mind that this is also a request by the application, not a requirement of the compositor to obey it. If there's not sufficient space where the application requests things then the compositor can just ignore it and do what it believes makes sense.