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
/*
     * (non-Javadoc)
     * 
     * @see org.eclipse.jface.window.Window#create()
     */
    public void create() {
        super.create();
        applyDialogFont(buttonBar);
    }
    /**
     * Get the IDialogBlockedHandler to be used by WizardDialogs and
     * ModalContexts.
     * 
     * @return Returns the blockedHandler.
     */
    public static IDialogBlockedHandler getBlockedHandler() {
        return blockedHandler;
    }
    /**
     * Set the IDialogBlockedHandler to be used by WizardDialogs and
     * ModalContexts.
     * 
     * @param blockedHandler
     *            The blockedHandler for the dialogs.
     */
    public static void setBlockedHandler(IDialogBlockedHandler blockedHandler) {
        Dialog.blockedHandler = blockedHandler;
    }
}