Select all checkbox with three states

Question

Remember installing a program for example and you can check individually each item or you can check a 'select all' check-box at the top? And when some lines are checked the 'select all' box has a green fill inside instead of a check or being empty?

What I'm trying to ask is what is the normal behavior for the 'select all' box?

For example if few lines are checked the box is green, now if I click the box everything gets selected, but when I click it again should everything deselect or should the individual boxes remember whether they were checked before I checked 'select all'?

Answer 1

Normal behaviour:

When you click the 'select all' box again everything should deselect. (This is the only way to deselect everything). If the user wants to revert back to how it was (the individual sub selections) then they either have to do this manually, or cancel and start over.