How can I style the Ace Editor Autocompletion Popup?

Question

When I embed the Ace Editor in a web page and enable autocompletion, I want to be able to style the autocompletion popup. How can this be done?

user_1519054 · Answer

It is possible using the css class .ace_editor.ace_autocomplete.

For example:

.ace_editor.ace_autocomplete {
    border: 1px solid rgba(0,0,0,.2)!important;
    width: 50% !important;
}