desktop-restore-forces-onscreen is a variable defined in `desktop.el'.
Its value is

If t, restores frames that are fully offscreen onscreen instead.
If `all', also restores frames that are partially offscreen onscreen.

Note that checking of frame boundaries is only approximate.
It can fail to reliably detect frames whose onscreen/offscreen state
depends on a few pixels, especially near the right / bottom borders
of the screen.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.4 of Emacs.