Bug 33550 [Dialogs] Dialog should support remembering size and position
There are several dialogs that remember its size and position. Since restore the size and considering screen size and font changes isn't trivial JFace's Dialog class should support remembering and restoring size and position. These would realy ease the task for subclasses. May be you can steel the code from OpenTypeSelectionDialog.
bundles/org.eclipse.jface/src/org/eclipse/jface/dialogs/Dialog.java
public static IDialogBlockedHandler blockedHandler = new IDialogBlockedHandler() {
        /*
         * (non-Javadoc)
         * 
         * @see org.eclipse.jface.dialogs.IDialogBlockedHandler#clearBlocked()
         */
        public void clearBlocked() {
            
        }
        /*
         * (non-Javadoc)
         * 
         * @see org.eclipse.jface.dialogs.IDialogBlockedHandler#showBlocked(org.eclipse.core.runtime.IProgressMonitor,
         *      org.eclipse.core.runtime.IStatus, java.lang.String)
         */
        public void showBlocked(IProgressMonitor blocking,
                IStatus blockingStatus, String blockedName) {
            
        }
        /*
         * (non-Javadoc)
         * 
         * @see org.eclipse.jface.dialogs.IDialogBlockedHandler#showBlocked(org.eclipse.swt.widgets.Shell,
         *      org.eclipse.core.runtime.IProgressMonitor,
         *      org.eclipse.core.runtime.IStatus, java.lang.String)
         */
        public void showBlocked(Shell parentShell, IProgressMonitor blocking,
                IStatus blockingStatus, String blockedName) {
            
        }