Bug 126527 [Field Assist] - API - Field Decoration alignment issues are different for cell editors
bundles/org.eclipse.jface/src/org/eclipse/jface/fieldassist/DecoratedField.java
* allocated by the hover.
		 */
		void dispose() {
			if (!hoverShell.isDisposed())
				hoverShell.dispose();
			if (region != null) {
				region.dispose();
			}
		}
		/*
		 * Set the visibility of the hover.
		 */
		void setVisible(boolean visible) {
			if (visible) {
				if (!hoverShell.isVisible())
					hoverShell.setVisible(true);
			} else {
				if (hoverShell.isVisible())
					hoverShell.setVisible(false);
			}
		}
		/*
		 * Set the text of the hover to the specified text. Recompute the size
		 * and location of the hover to hover near the specified control,
		 * pointing the arrow toward the target control.
		 */
		void setText(String t, Control hoverNear, Control targetControl) {
			if (t == null)
				t = EMPTY;
			if (!t.equals(text)) {