Frequently Asked Questions

Problems with the escape key in the terminal

A common problem when using Evil in terminal mode is a certain delay after pressing the escape key. Even more, when pressing the escape key followed quickly by another key the command is recognized as M-<key> instead of two separate keys: ESC followed by <key>. In fact, it is perfectly valid to simulate M-<key> by pressing ESC <key> quickly (but see below).

The reason for this is that in terminal mode a key sequence involving the meta key (or alt key) always generates a so called “escape sequence”, i.e. a sequence of two events sent to Emacs, the first being ESC and the second the key pressed simultaneously. The problem is that pressing the escape key itself also generates the ESC event. Thus, if Emacs (and therefore Evil) receives an ESC event there is no way to tell whether the escape key has been pressed (and no further event will arrive) or a M-<key> combination has been pressed (and the <key> event will arrive soon). In order to distinguish both situations Evil does the following. After receiving an ESC event Evil waits for a short time period (specified by the variable evil-esc-delay which defaults to 0.01 seconds) for another event. If no other event arrives Evil assumes that the plain escape key has been pressed, otherwise it assumes a M-<key> combination has been pressed and combines the ESC event with the second one. Because a M-<key> sequence usually generates both events in very quick succession, 0.01 seconds are usually enough and the delay is hardly noticeable by the user.

If you use a terminal multiplexer like tmux or screen the situation may be worse. These multiplexers have exactly the same problem recognizing M-<key> sequences and often introduce their own delay for the ESC key. There is no way for Evil to influence this delay. In order to reduce it you must reconfigure your terminal multiplexer.

Note that this problem should not arise when using Evil in graphical mode. The reason is that in this case the escape key itself generates a different command, namely escape (a symbol) and hence Evil can distinguish whether the escape key or a M-<key> combination has been pressed. But this also implies that pressing ESC followed by <key> cannot be used to simulate M-<key> in graphical mode!

Underscore is not a word character

An underscore _ is a word character in Vim. This means that word motions like w skip over underlines in a sequence of letters as if it was a letter itself. In contrast, in Evil the underscore is often a non-word character like operators, e.g. +.

The reason is that Evil uses Emacs’ definition of a word and this definition does often not include the underscore. In Emacs word characters are determined by the syntax-class of the buffer. The syntax-class usually depends on the major-mode of this buffer. This has the advantage that the definition of a “word” may be adapted to the particular type of document being edited. Evil uses Emacs’ definition and does not simply use Vim’s definition in order to be consistent with other Emacs functions. For example, word characters are exactly those characters that are matched by the regular expression character class [:word:].

If you want the underscore to be recognised as word character, you can modify its entry in the syntax-table:

(modify-syntax-entry ?_ "w")

This gives the underscore the ‘word’ syntax class. You can use a mode-hook to modify the syntax-table in all buffers of some mode, e.g.:

(add-hook 'c-mode-common-hook
          (lambda () (modify-syntax-entry ?_ "w")))

This gives the underscore the word syntax-class in all C-like buffers.

Similarly to Emacs’ definition of a word, the definition of a “symbol” is also dependent on the syntax-class of the buffer, which often includes the underscore. The default text objects keymap associates kbd::o with the symbol object, making kbd::cio a good alternative to Vim’s kbd::ciw, for example. The following will swap between the word and symbol objects in the keymap:

(define-key evil-outer-text-objects-map "w" 'evil-a-symbol)
(define-key evil-inner-text-objects-map "w" 'evil-inner-symbol)
(define-key evil-outer-text-objects-map "o" 'evil-a-word)
(define-key evil-inner-text-objects-map "o" 'evil-inner-word)

This will not change the motion keys, however. One way to make word motions operate as symbol motions is to alias the evil-word thing [1] to the evil-symbol thing:

(defalias 'forward-evil-word 'forward-evil-symbol)

Footnotes

[1]Many of Evil’s text objects and motions are defined in terms of the thingatpt library, which in this case are defined entirely in terms of forward-THING functions. Thus aliasing one to another should make all motions and text objects implemented in terms of that thing behave the same.