Bug 294462 [FieldAssist] ControlDecoration#showHoverText doesn't check if the widget is visible
If the HOVER-Text is set on decoration of a widget which is invisible the Hover-Shell is still poping up because it doesn't check if the control is invisible make the Hover appearing somewhere on the screen.
bundles/org.eclipse.jface/src/org/eclipse/jface/fieldassist/ControlDecoration.java
}
		};
		printAddListener(control, "FOCUS"); 
		control.addFocusListener(focusListener);
		
		paintListener = new PaintListener() {
			public void paintControl(PaintEvent event) {
				Control control = (Control) event.widget;
				Rectangle rect = getDecorationRectangle(control);
				if (shouldShowDecoration()) {
					event.gc.drawImage(getImage(), rect.x, rect.y);
				}
			}
		};
		
		
		mouseMoveListener = new MouseMoveListener() {
			public void mouseMove(MouseEvent event) {
				if (showHover) {
					if (!decorationRectangle.contains(event.x, event.y)) {
						hideHover();
						
						printRemoveListener(event.widget, "MOUSEMOVE"); 
						((Control) event.widget)
								.removeMouseMoveListener(mouseMoveListener);
						moveListeningTarget = null;
					}
				}
			}
		};