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#### 20.7.12 Classifying Events

Every event has an event type, which classifies the event for key binding purposes. For a keyboard event, the event type equals the event value; thus, the event type for a character is the character, and the event type for a function key symbol is the symbol itself. For events that are lists, the event type is the symbol in the CAR of the list. Thus, the event type is always a symbol or a character.

Two events of the same type are equivalent where key bindings are concerned; thus, they always run the same command. That does not necessarily mean they do the same things, however, as some commands look at the whole event to decide what to do. For example, some commands use the location of a mouse event to decide where in the buffer to act.

Sometimes broader classifications of events are useful. For example, you might want to ask whether an event involved the `META` key, regardless of which other key or mouse button was used.

The functions `event-modifiers` and `event-basic-type` are provided to get such information conveniently.

Function: event-modifiers event

  This function returns a list of the modifiers that event has. The modifiers are symbols; they include `shift`, `control`, `meta`, `alt`, `hyper` and `super`. In addition, the modifiers list of a mouse event symbol always contains one of `click`, `drag`, and `down`. For double or triple events, it also contains `double` or `triple`.

  The argument event may be an entire event object, or just an event type. If event is a symbol that has never been used in an event that has been read as input in the current Emacs session, then `event-modifiers` can return `nil`, even when event actually has modifiers.

  Here are some examples:

      (event-modifiers ?a)
           ⇒ nil
      (event-modifiers ?A)
           ⇒ (shift)
      (event-modifiers ?\C-a)
           ⇒ (control)
      (event-modifiers ?\C-%)
           ⇒ (control)
      (event-modifiers ?\C-\S-a)
           ⇒ (control shift)
      (event-modifiers 'f5)
           ⇒ nil
      (event-modifiers 's-f5)
           ⇒ (super)
      (event-modifiers 'M-S-f5)
           ⇒ (meta shift)
      (event-modifiers 'mouse-1)
           ⇒ (click)
      (event-modifiers 'down-mouse-1)
           ⇒ (down)

  The modifiers list for a click event explicitly contains `click`, but the event symbol name itself does not contain ‘`click`’.

Function: event-basic-type event

  This function returns the key or mouse button that event describes, with all modifiers removed. The event argument is as in `event-modifiers`. For example:

      (event-basic-type ?a)
           ⇒ 97
      (event-basic-type ?A)
           ⇒ 97
      (event-basic-type ?\C-a)
           ⇒ 97
      (event-basic-type ?\C-\S-a)
           ⇒ 97
      (event-basic-type 'f5)
           ⇒ f5
      (event-basic-type 's-f5)
           ⇒ f5
      (event-basic-type 'M-S-f5)
           ⇒ f5
      (event-basic-type 'down-mouse-1)
           ⇒ mouse-1

Function: mouse-movement-p object

  This function returns non-`nil` if object is a mouse movement event. See Motion Events.

Function: event-convert-list list

  This function converts a list of modifier names and a basic event type to an event type which specifies all of them. The basic event type must be the last element of the list. For example,

      (event-convert-list '(control ?a))
           ⇒ 1
      (event-convert-list '(control meta ?a))
           ⇒ -134217727
      (event-convert-list '(control super f1))
           ⇒ C-s-f1

Next: Accessing Mouse, Previous: Event Examples, Up: Input Events [Contents][Index]