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
* has been called.
     * </p>
     * <p>
     * Clients may call this framework method, but should not override it.
     * </p>
     * 
     * @param dlus
     *            the number of horizontal dialog units
     * @return the number of pixels
     */
    protected int convertHorizontalDLUsToPixels(int dlus) {
        
        if (fontMetrics == null)
            return 0;
        return convertHorizontalDLUsToPixels(fontMetrics, dlus);
    }
    /**
     * Returns the number of pixels corresponding to the given number of
     * vertical dialog units.
     * <p>
     * This method may only be called after <code>initializeDialogUnits</code>
     * has been called.
     * </p>
     * <p>
     * Clients may call this framework method, but should not override it.
     * </p>
     * 
     * @param dlus
     *            the number of vertical dialog units
     * @return the number of pixels