a small suggestion .. but though i wont be a right approach
use stretch factors vertical stretch or horizontal stretch and spacers
http://qt-project.org/doc/qt-4.8/qspaceritem.html
and
http://qt-project.org/doc/qt-4.8/lay...tretch-factors

spacer will make the area reserve for the widget u show and hide..

instead I would like the window to actually shrink
resizeEvent() and setFixedSize() can help u ..