Unless yo do something specific to size the dialog it will autosize to reflect the controls it contains. I have seen very wide dialogs resulting from having a ViewList control which resizes to contain a long view id. I tend to limit the size of my ViewList controls using the setMaxWidth method to avoid this. Generally all controls, including dialogs, have setMax[Width/Height/Size], setMin[Width/Height/Size], setFixed[Width/Height/Size] methods which allow you to manipulate as you wish.
Hope this helps.
