Converting layouts in Qt3 to Qt4 involves:

The old-style QLayout(QLayout* parent) needs to be replaced by a new
empty contructor and a subsequent parent->addLayout(child) statement.

Example Qt3:

QVBoxLayout *vbox = new QVBoxLayout ( this );
QHBoxLayout *box3 = new QVBoxLayout ( vbox );
QVBoxLayout *box4 = new QVBoxLayout ( box3 );
QVBoxLayout *box5 = new QVBoxLayout ( box3 );
QHBoxLayout *box6 = new QVBoxLayout ( vbox );

Ported to Qt4:

QVBoxLayout *vbox = new QVBoxLayout( this );
QHBoxLayout *box3 = new QHBoxLayout;
QVBoxLayout *box4 = new QVBoxLayout;
QVBoxLayout *box5 = new QVBoxLayout;
QHBoxLayout *box6 = new QHBoxLayout;

vbox->addLayout(box3);
box3->addLayout(box4);
box3->addLayout(box5);
vbox->addLayout(box6);