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
case SWT.LEFT | SWT.BOTTOM:
			return LEFT_BOTTOM;
		case SWT.RIGHT | SWT.TOP:
			return RIGHT_TOP;
		case SWT.RIGHT | SWT.BOTTOM:
			return RIGHT_BOTTOM;
		default:
			return LEFT_TOP;
		}
	}
	/*
	 * Create a form data that will place the decoration at the specified
	 * position.
	 * 
	 * @param index the index in the decDatas describing the position of the
	 * decoration.
	 * 
	 * @param image the image shown in the decoration.
	 * 
	 */
	private FormData createFormDataForIndex(int index, Image image) {
		Assert.isTrue(index >= 0 && index < DECORATION_SLOTS,
				"Index out of range"); 
		FormData data = new FormData();
		switch (index) {
		case LEFT_TOP:
			data.left = new FormAttachment(0, 0);
			data.top = new FormAttachment(0, 0);
			break;
		case LEFT_BOTTOM: