Definition
UI Events defines UIEvent
[Exposed=Window]
interface UIEvent : Event {
  constructor(DOMString type, optional UIEventInit eventInitDict = {});
  readonly attribute Window? view;
  readonly attribute long detail;
};
partial interface UIEvent {
  // Deprecated in this specification
  undefined initUIEvent(DOMString typeArg,
    optional boolean bubblesArg = false,
    optional boolean cancelableArg = false,
    optional Window? viewArg = null,
    optional long detailArg = 0);
};
partial interface UIEvent {
  // The following support legacy user agents
  readonly attribute unsigned long which;
};This interface is extended in the following specifications:
- Input Device Capabilitiespartial interface UIEvent { readonly attribute InputDeviceCapabilities? sourceCapabilities; };
Consolidated IDL (across mixin and partials)
[Exposed=Window]
interface UIEvent : Event {
  constructor(DOMString type, optional UIEventInit eventInitDict = {});
  readonly attribute Window? view;
  readonly attribute long detail;
  // Deprecated in this specification
  undefined initUIEvent(DOMString typeArg,
    optional boolean bubblesArg = false,
    optional boolean cancelableArg = false,
    optional Window? viewArg = null,
    optional long detailArg = 0);
  // The following support legacy user agents
  readonly attribute unsigned long which;
  readonly attribute InputDeviceCapabilities? sourceCapabilities;
};Methods and attributes that return objects implementing UIEvent
  
Referring IDL interfaces/dictionaries
Referring specifications
- Input Device Capabilities refers to UIEvent
- CSS Spatial Navigation Module Level 1 refers to UIEvent
- Touch Events - Level 2 refers to UIEvent