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 would be satisfied by having the * and # searches
use symbols instead of words, this can be achieved by setting the
evil-symbol-word-search
variable to t
.
If you want the underscore to be recognised as word character for other motions, 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. |