You just need to set the Vertical Stretch (in Property-Editor QWidget.sizePolicy.Vertical Stretch) of your custom-Widget to 1, and the one of your QHBoxLayout to 0.
Stretch: http://doc.trolltech.com/4.6/layout....tretch-factors . The remaining available space is divided proportional to the stretchfactors.
Then you should also use a QVBoxLayout, as in your case the SpinBoxCell should never get a bigger height, and thus the user shall not be able to change it by means of a splitter.
HIH
Johannes
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