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
for (int i = 0; i < DECORATION_SLOTS; i++) {
			if (decDatas[i] != null && dec == decDatas[i].decoration
					&& decDatas[i].label != null
					&& !decDatas[i].label.isDisposed())
				return decDatas[i];
		}
		return null;
	}
	/*
	 * Show the specified text in the hover, positioning the hover near the
	 * specified control.
	 */
	private void showHoverText(String text, Control hoverNear) {
		if (text == null) {
			hideHover();
			return;
		}
		if (hover == null) {
			hover = new Hover(hoverNear.getShell());
		}
		hover.setText(text, hoverNear, control);
		hover.setVisible(true);
	}
	/**
	 * Set a boolean that indicates whether the receiver should use the
	 * decoration registry's maximum decoration width when allocating space for
	 * decorations. The default value is <code>true</code>. Using the maximum
	 * decoration width is useful so that decorated fields on the same dialog
	 * that have different decoration widths will all align. This also allows
	 * client dialogs to align non-decorated fields with decorated fields by