Bug 129214 [Field Assist] - Decorated Field attachments not centering images horizontally
DecoratedField is supposed to center decorations horizontally on each side. The current attachments are not doing so. Also consider whether grid would have been a better choice for internal implementation.
bundles/org.eclipse.jface/src/org/eclipse/jface/fieldassist/DecoratedField.java
private static final String EMPTY = ""; 
		/**
		 * Offset of info hover arrow from the left or right side.
		 */
		private int hao = 10;
		/**
		 * Width of info hover arrow.
		 */
		private int haw = 8;