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
* <p>
     * The <code>Dialog</code> implementation of this framework method creates
     * a standard push button, registers it for selection events including
     * button presses, and registers default buttons with its shell. The button
     * id is stored as the button's client data. If the button id is
     * <code>IDialogConstants.CANCEL_ID</code>, the new button will be
     * accessible from <code>getCancelButton()</code>. If the button id is
     * <code>IDialogConstants.OK_ID</code>, the new button will be accesible
     * from <code>getOKButton()</code>. Note that the parent's layout is
     * assumed to be a <code>GridLayout</code> and the number of columns in
     * this layout is incremented. Subclasses may override.
     * </p>
     * 
     * @param parent
     *            the parent composite
     * @param id
     *            the id of the button (see <code>IDialogConstants.*_ID</code>
     *            constants for standard dialog button ids)
     * @param label
     *            the label from the button
     * @param defaultButton
     *            <code>true</code> if the button is to be the default button,
     *            and <code>false</code> otherwise
     * 
     * @return the new button
     * 
     * @see #getCancelButton
     * @see #getOKButton()
     */
    protected Button createButton(Composite parent, int id, String label,