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
* images are managed by the dialog framework, and must not be disposed by
     * another party.
     * 
     * @param key
     *            one of the <code>Dialog.DLG_IMG_* </code> constants
     * @return the standard dialog image
     */
    public static Image getImage(String key) {
        return JFaceResources.getImageRegistry().get(key);
    }
    /**
     * Returns the button created when <code>createButton</code> is called
     * with an ID of <code>IDialogConstants.OK_ID</code>. If
     * <code>createButton</code> was never called with this parameter, or if
     * <code>createButton</code> is overridden, <code>getOKButton</code>
     * will return <code>null</code>.
     * 
     * @return the OK button or <code>null</code>
     * 
     * @see #createButton(Composite, int, String, boolean)
     * @since 2.0
     * @deprecated Use <code>getButton(IDialogConstants.OK_ID)</code> instead.
     *             This method will be removed soon.
     */
    protected Button getOKButton() {
        return getButton(IDialogConstants.OK_ID);
    }
    /**
     * Initializes the computation of horizontal and vertical dialog units based
     * on the size of current font.