Standard drop-down menus that contain sub-menus very often have no concept of user intent, and this can lead to a repeating frustration that most of us have likely run into: straying off course by even a single pixel can cause the sub-menu to close instantly. Ways around this include adding a delay to try and account for user error, but that doesn’t feel as snappy. Amazon has a really clever solution that accounts for user error yet responds instantly:
At every position of the [pointer] you can picture a triangle between the current mouse position and the upper and lower right corners of the dropdown menu. If the next mouse position is within that triangle, the user is probably moving their [pointer] into the currently displayed submenu. Amazon uses this for a nice effect. As long as the [pointer] stays within that blue triangle the current submenu will stay open. It doesn’t matter if the [pointer] hovers over “Appstore for Android” momentarily – the user is probably heading toward “Learn more about Cloud Drive.”
And if the [pointer] goes outside of the blue triangle, they instantly switch the submenu, giving it a really responsive feel.
So if you’re as geeky as me and think something this trivial is cool, I made a jQuery plugin that fires events when detecting this sort of directional menu aiming: jQuery-menu-aim.
See the source link for more.