run the attached wrapped-menubar.zul
1. Open (Click) "Menu First Row 1"
2. Try move your mouse down in order to click Item 1 or 2
This will be quite difficult. In most cases the "Menu Second Row 1" will open before the user has the chance to click a menu item (you need to move the mouse very fast in order to stay in "Menu First Row 1")
There is a visual gap (3px) between the <menu> and the <menupopup>
When moving the mouse over this gap the <menu> in the second row gets activated.
the attachment contains a commented out CSS workaround using a an invisible ::after pseudo element to "close the gap" preventing mouse events from reaching the <menu> in the second row.