There are the following options of the overfull lines handling:

•Allow: this is the default behaviour, and the behaviour of the justification in all previous versions.

•Avoid only in shaped areas becoming wider: this will insert empty line BUT ONLY if the geometry widens after the line's position - i.e. if it is possible to avoid the overfull line moving it down in the geometry. In other words when a potential overfull line is detected, the justification algorithm inserts empty lines until it reaches a point in the geometry where the line will fit, or if this is not possible until it reaches a point in the geometry wider that the original one, but still with an overfull line.

•Avoid always: This means that when an overfull line is detected the justification algorithm will insert empty lines until it reaches a point in the geometry where the line fits, or until the line is out of the geometry entirely (overset). With this setting overfull lines will be always avoided, but if the geometry is too narrow all the text will become overset.