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
ImageRegistry reg = JFaceResources.getImageRegistry();
        reg.put(DLG_IMG_MESSAGE_INFO, ImageDescriptor.createFromFile(
                Dialog.class, "images/message_info.gif")); 
        reg.put(DLG_IMG_MESSAGE_WARNING, ImageDescriptor.createFromFile(
                Dialog.class, "images/message_warning.gif")); 
        reg.put(DLG_IMG_MESSAGE_ERROR, ImageDescriptor.createFromFile(
                Dialog.class, "images/message_error.gif")); 
    }
    /**
     * The dialog area; <code>null</code> until dialog is layed out.
     */
    protected Control dialogArea;
    /**
     * The button bar; <code>null</code> until dialog is layed out.
     */
    public Control buttonBar;
    /**
     * Collection of buttons created by the <code>createButton</code> method.
     */
    private HashMap buttons = new HashMap();
    /**
     * Font metrics to use for determining pixel sizes.
     */
    private FontMetrics fontMetrics;
    /**
     * Number of horizontal dialog units per character, value <code>4</code>.
     */
    private static final int HORIZONTAL_DIALOG_UNIT_PER_CHAR = 4;
    /**
     * Number of vertical dialog units per character, value <code>8</code>.