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
*            if no text should be shown.
	 */
	public void showHoverText(String text) {
		showHoverText(text, control);
	}
	/**
	 * Hide any hover popups that are currently showing on the control.
	 * Normally, a decoration's description text will be shown in an info hover
	 * over the field's control as long as the mouse hovers over the decoration,
	 * and will be hidden when the mouse exits the control. This method can be
	 * used to hide a hover that was shown using <code>showHoverText</code>,
	 * or to programatically hide the current decoration hover.
	 * 
	 * <p>
	 * This message has no effect if there is no current hover.
	 * 
	 */
	public void hideHover() {
		if (hover != null) {
			hover.setVisible(false);
		}
	}
	/*
	 * The target control gained focus. Any decorations that should show only
	 * when they have the focus should be shown here.
	 */
	private void controlFocusGained() {
		for (int i = 0; i < DECORATION_SLOTS; i++) {
			if (decDatas[i] != null && decDatas[i].showOnFocus)
				setVisible(decDatas[i], true);