The Changelog for version 0.15.0 is available here.

A lot of the changes for this release aren't very user-visible, although they
are important in improving the usability. The main change is the move from the
standard set-transient-map to my own hydra-set-transient-map.

This change has allowed to remove the part where the amaranth and pink hydras
intercept a binding which doesn't belong to them and then try to forward it back
to Emacs. It was done in this way, which might be interesting for people who
write Elisp:

(define-key hydra-keymap t 'hydra-intercept)

Binding t means that when the keymap is active, any binding which doesn't
belong to the keymap will be interpreted as t. Then, I would use lookup-key
and this-command-keys and try to call the result. That method was quite
fragile:

• It didn't work for prefix keys while a pink hydra was active.
• It didn't work for some keys in the terminal because of input-decode-map.

The new method solves the mentioned issues by not using t and instead running
this function in the pre-command-hook:

(defun hydra--clearfun ()
  "Disable the current Hydra unless `this-command' is a head."
  (if (memq this-command '(handle-switch-frame
                           keyboard-quit))
      (hydra-disable)
    (unless (eq this-command
                (lookup-key hydra-curr-map
                            (this-single-command-keys)))
      (unless (cl-case hydra-curr-foreign-keys
                (warn
                 (setq this-command 'hydra-amaranth-warn))
                (run
                 t)
                (t nil))
        (hydra-disable)))))

This approach is actually very similar to what the built-in set-transient-map
does from Emacs 24.4 onward. Of course, changing the a large cog in the Hydra
mechanism can lead to some new bugs, or even old bugs to re-surface. So I really
appreciate the help from @jhonnyseven in testing the new code.

As always, if you find something very broken, you can roll back to the GNU ELPA version
and raise an issue.

Fixes

single command red/blue issue

Fix the uniqueness issue, when a single command is assigned to both a
red and a blue head.

Here's an example:

(defhydra hydra-zoom (global-map "<f2>")
  "zoom"
  ("g" text-scale-increase "in")
  ("l" text-scale-decrease "out")
  ("r" (text-scale-set 0) "reset")
  ("0" (text-scale-set 0) :bind nil :exit t)
  ("1" (text-scale-set 0) nil :bind nil :exit t))

Here, three heads are assigned (text-scale-set 0), however their behavior is different:

• r doesn't exit and has a string hint.
• 0 exits and has an empty hint (so only the key is in the docstring).
• 1 exits and has a nil hint (will not be displayed in the docstring).

The latter two call hydra-zoom/lambda-0-and-exit, while r
calls hydra-zoom/lambda-r.

Don't default hydra-repeast--prefix-arg to 1

See #61 for more info.

Allow hydra-repeat to take a numeric arg

For hydra-vi, it's now possible to do this 4j.2...
The line will be forwarded:

• 4 times by 4j
• 4 times by .
• 2 times by 2.
• 2 times by .

See #92 for more info.

Key chord will be disabled for the duration of a hydra

This means that hydras have become much more easy to use with key chords. For
instance, if dj key chord calls a hydra or is part of the hydra, you
won't call the jj key chord by accident with djj.

See #97 for more info.

New Features

Variable as a string docstring spec

You can now use this form in your hydras:

(defvar foo "a b c")
(defhydra bar ()
  "
  bar %s`foo
"
  ("a" 't)
  ("q" nil))

Previously, it would only work for %s(foo) forms.

:bind property can now also be a keymap

If you remember, you can set :bind in the body to define in which way the
heads should be bound outside the Hydra. You also assign/override :bind for
each head. This is especially useful to set :bind to nil for a few heads that
you don't want to bind outside.

Previously, :bind could be either a lambda or nil. Now a keymap is also accepted.

Integration tests

In addition to the abundant macro-expansion tests, integration tests are now
also running, both for emacs24 and for emacs-snapshot. This means that hydra
should be a lot more stable now.

Here's an example test:

(defhydra hydra-simple-1 (global-map "C-c")
  ("a" (insert "j"))
  ("b" (insert "k"))
  ("q" nil))

(ert-deftest hydra-integration-1 ()
  (should (string= (hydra-with "|"
                               (execute-kbd-macro
                                (kbd "C-c aabbaaqaabbaa")))
                   "jjkkjjaabbaa|"))
  (should (string= (hydra-with "|"
                               (condition-case nil
                                   (execute-kbd-macro
                                    (kbd "C-c aabb C-g"))
                                 (quit nil))
                               (execute-kbd-macro "aaqaabbaa"))
                   "jjkkaaqaabbaa|")))

In the tests above, hydra-simple is a defined and bound hydra. "|"
represents the buffer text (empty), where | is the point position.
And (kbd "C-c aabbaaqaabbaa") represents the key sequence that you can normally press by hand.
Finally, "jjkkjjaabbaa|" is what the buffer and the point position should look like afterwards.
If you find a hydra bug, it would be really cool to submit a new integration test to make sure that
this bug doesn't happen in the future.

Basic error handling

I really like the use-package feature where it catches load-time errors and issues a message instead of bringing up the debugger. This is really useful, since it's hard to fix the bug with a mostly broken Emacs, in the case when the error happened early in the load process. So the same behavior now happens with defhydra. In case of an error, defhydra will be equivalent to a no-op, and the error message will be written to the *Messages* buffer.

Use a variable instead of a function for the hint

This leads up to the yet unresolved #86, which asks
for heads to be activated conditionally.

For now, you can modify the docstring on your own if you wish.
Here's some code from the expansion of hydra-zoom to explain what I mean:

(set
 (defvar hydra-zoom/hint nil
   "Dynamic hint for hydra-zoom.")
 '(format
   #("zoom: [g]: in, [l]: out."
     7 8 (face hydra-face-red)
     16 17 (face hydra-face-red))))
;; in head body:
(when hydra-is-helpful
  (if hydra-lv
      (lv-message
       (eval hydra-zoom/hint))
    (message
     (eval hydra-zoom/hint))))

Eventually, I'll add some automatic stuff to fix #86. But for now, you can
experiment with modifying e.g. hydra-zoom/hint inside heads, if you want.

Multiple inheritance for Hydra heads

Each hydra, e.g. hydra-foo will now declare its own heads as a variable
hydra-foo/heads. It's possible to inherit them like this:

(defhydra hydra-zoom (global-map "<f2>")
  "zoom"
  ("g" text-scale-increase "in")
  ("s" text-scale-decrease "out"))

(defhydra hydra-arrows ()
  ("h" backward-char "left")
  ("j" next-line "down")
  ("k" previous-line "up")
  ("l" forward-char "right"))

(defhydra hydra-zoom-child (:inherit (hydra-zoom/heads hydra-arrows/heads)
                            :color amaranth)
  "zoom"
  ("q" nil))

Here, hydra-zoom-child inherits the heads of hydra-zoom and hydra-arrows.
It adds one more head q to quit. Also, it changes the color to
amaranth, which means that it's only possible to exit it with q or
C-g. This hydra's parents remain at their original (red) color.

See #57 for more info.

Fixes

• Handling of heads with duplicate cmd was improved.
• Don't bind nil in outside keymaps.
• Work-around golden-ratio-mode in lv-window.
• C-g (hydra-keyboard-quit) should run :post.
• Bind [switch-frame] to hydra-keyboard-quit.
• :post is called for :timeout.

New Features

• hydra-key-format-spec is a new defcustom for the keys format in the docstring. It's "%s" by
  default, but you can set it to e.g. "%-4s" if you like.
• The key regex was extended to include most common key binding characters.
• hydra-repeat is a hydra-specific repeat function. It behaves as you would expect repeat to behave.
• New body option - :timeout. Use e.g. :timeout 2.0 to set the timer. After the first head is called,
  a timer is started to disable the hydra. Each new head call resets this timer, so the hydra won't disappear as long as you keep typing.
• Lines are truncated in lv-message. This is useful for large docstring not to become misaligned when the window
  becomes too small.

Allow for a %s(test) spec in docstring

The spec that's used for e.g. (test) is %S. So if (test) returns a string, it will be quoted.
This may not be desired, hence the new feature.
Example:

(defhydra hydra-marked-items (dired-mode-map "")
  "
Number of marked items: %(length (dired-get-marked-files))
Directory size: %s(shell-command-to-string \"du -hs\")
"
  ("m" dired-mark "mark"))

Emulate org-mode export dispatch with hydra-ox

You can also look at that code to see how nested hydras work. Several other examples were added to
hydra-examples.el.

The pink/amaranth override is set recursively

This fixes the issue in this hydra:

(defhydra hydra-test (:color amaranth)
  "foo"
  ("fo" (message "yay"))
  ("q" nil))

Before, pressing e.g. fp would not issue a warning, since f started its own
keymap. This is now fixed.

An option to specify the hint for all heads in body

When you write a large docstring, you usually pass nil as the hint for most heads.
Now you can omit it, if you set :hint nil in body.
Example:

(defhydra hydra-org-template (:color blue :hint nil)
  "
_c_enter  _q_uote    _L_aTeX:
_l_atex   _e_xample  _i_ndex:
_a_scii   _v_erse    _I_NCLUDE:
_s_rc     ^ ^        _H_TML:
_h_tml    ^ ^        _A_SCII:
"
  ("s" (hot-expand "<s"))
  ("e" (hot-expand "<e"))
  ("q" (hot-expand "<q"))
  ("v" (hot-expand "<v"))
  ("c" (hot-expand "<c"))
  ("l" (hot-expand "<l"))
  ("h" (hot-expand "<h"))
  ("a" (hot-expand "<a"))
  ("L" (hot-expand "<L"))
  ("i" (hot-expand "<i"))
  ("I" (hot-expand "<I"))
  ("H" (hot-expand "<H"))
  ("A" (hot-expand "<A"))
  ("<" self-insert-command "ins")
  ("o" nil "quit"))

Fixes

• Emacs 24.3 (and maybe earlier versions) compatibility added
• (hydra-cleanup): Should not delete buffer first when window is dedicated.
• (lv-message): Should not deactivate mark.
• quit signals are intercepted, so that proper clean-up is done.
• no defuns with the same name will be generated in case some heads' cmd parts coincide

New Features

Pink body color

When body color is pink, and hydra intercepts a binding which isn't a head, instead of quitting the
hydra and executing the binding (default red behavior), it will execute the binding and not quit
the hydra.

So now, pink and amaranth are body colors that are a flavor of the default red that, instead of
quitting when a non-head binding is intercepted, respectively run the binding or issue a warning.

Teal body color

Teal color behaves similarly to amaranth (issues a warning when intercepting foreign bindings),
but the default behavior for each head is to quit.

The following evaluates to true:

(equal
 (macroexpand
  '(defhydra hydra-test (:color amaranth)
    ("a" fun-a)
    ("b" fun-b :color blue)
    ("c" fun-c :color blue)
    ("d" fun-d :color blue)
    ("e" fun-e :color blue)
    ("f" fun-f :color blue)))
 (macroexpand
  '(defhydra hydra-test (:color teal)
    ("a" fun-a :color red)
    ("b" fun-b)
    ("c" fun-c)
    ("d" fun-d)
    ("e" fun-e)
    ("f" fun-f))))

So if you want to write less, use teal color in this case.

Alternative color-less syntax

The color syntax is working quite well, since I was able to keep an almost full backward-compatibility:
once you pinpoint a color it will have that behavior, all the new behaviors will be released under a new color.

Some might prefer an alternative set of switches rather than colors. New compat switches are:

- ":exit nil" for ":color red"; You don't have to specify either
  option in the body, since they are the default behavior that was
  available on Hydra release
- ":exit t" for ":color blue"
- ":foreign-keys warn" for ":color amaranth"
- ":foreign-keys warn :exit t" for ":color teal"
- ":foreign-keys run" for ":color pink"

The property :exit can be inherited and overridden in the same way as :color red or blue.

The following evaluates to true:

(equal
 (macroexpand
  '(defhydra hydra-test ()
    ("a" fun-a)
    ("b" fun-b :color blue)
    ("c" fun-c :color blue)
    ("d" fun-d :color blue)
    ("e" fun-e :color blue)
    ("f" fun-f :color blue)))
 (macroexpand
  '(defhydra hydra-test (:color blue)
    ("a" fun-a :color red)
    ("b" fun-b)
    ("c" fun-c)
    ("d" fun-d)
    ("e" fun-e)
    ("f" fun-f))))

The following two are exactly the same as the two above:

(equal
 (macroexpand
  '(defhydra hydra-test ()
    ("a" fun-a)
    ("b" fun-b :exit t)
    ("c" fun-c :exit t)
    ("d" fun-d :exit t)
    ("e" fun-e :exit t)
    ("f" fun-f :exit t)))
 (macroexpand
  '(defhydra hydra-test (:exit t)
    ("a" fun-a :exit nil)
    ("b" fun-b)
    ("c" fun-c)
    ("d" fun-d)
    ("e" fun-e)
    ("f" fun-f))))

Ruby-style string interpolation in docstrings

Here's an example:

(defhydra hydra-marked-items (dired-mode-map "")
  "
Number of marked items: %(length (dired-get-marked-files))
Auto-revert mode is:    %`auto-revert-mode
"
      ("m" dired-mark "mark"))

To enable the behavior, the docstring has to start with a newline (which will be stripped). This
makes sense, since you usually want to align extensive docstrings, like I did this one. The escape
syntax for variables is such that you can auto-complete them with company-mode. Both variables
and sexps can use format style width specifiers. See the documentation of format for more
details.

Examples 7-9 added to hydra-examples.el

These examples explain Ruby-style interpolation.

Updated faces

I've updated each face to match their color by default. Remember, that you can customize each
face interactively with M-x customize-group hydra.

Alternative grey-scale or custom faces

If you don't want colors for some reason, you can customize hydra-fontify-head-function to your
taste.

As an example:

(setq hydra-fontify-head-function
      #'hydra-fontify-head-greyscale)

This function is already defined in hydra.el, but you could define a similar one on your own:

(defun hydra-fontify-head-greyscale (head body)
  "Produce a pretty string from HEAD and BODY.
HEAD's binding is returned as a string wrapped with [] or {}."
  (let ((color (hydra--head-color head body)))
    (format
     (if (eq color 'blue)
         "[%s]"
       "{%s}") (car head))))

New switch :body-pre

This sexp or function will be prepended to the prefix/body function.
Here's an example of use:

(defvar hydra-vi/init-pos nil)
(defhydra hydra-vi (:body-pre (setq hydra-vi/init-pos (point))
                    :color pink)
  "vi"
  ;; arrows
  ("h" backward-char)
  ("j" next-line)
  ("k" previous-line)
  ("l" forward-char)
  ;; exit points
  ("q" (goto-char hydra-vi/init-pos) "ins" :exit t)
  ("C-n" (forward-line 1) nil :exit t)
  ("C-p" (forward-line -1) nil :exit t))

Here, upon entering the hydra, the point position will be saved. And upon quitting, it will be
restored.

New features

Define Hydra heads that don't show up in the hint at all

This can be done by setting the head's hint explicitly to nil, instead of the usual string. For
instance, if you always tend to bind the arrows to hjkl, there's no point to show a hint
for them.

Use a dedicated window for Hydra hints

Since version 0.10.0, setting hydra-lv to t (the default setting) will make it use a dedicated
window right above the Echo Area for hints. This has the advantage that you can immediately see any
message output from the functions that you call, since Hydra no longer uses message to display
the hint. You can still have the old behavior by setting hydra-lv to nil.

Allow duplicate functions in heads

Duplicate functions will be concatenated in the hint.

Example:

(defhydra hydra-zoom (global-map "<f2>")
  "zoom"
  ("g" text-scale-increase "in")
  ("l" text-scale-decrease "out")
  ("0" (text-scale-set 0) "reset")
  ("1" (text-scale-set 0) :bind nil)
  ("2" (text-scale-set 0) :bind nil :color blue))

Here, the hint will be: "zoom: [g]: in, [l]: out, [0 1 2]: reset.", and "2" will be colored blue.

Add option to font-lock defhydra

If you want to nicely font-lock your defhydra statements, just add this to your config:

(require 'hydra)
(hydra-add-font-lock)

Additionally, defhydra is now to be indented as a defun, so it will be indented like this:

(defhydra hydra-goto-line (global-map "M-g"
                           :pre (linum-mode 1)
                           :post (linum-mode -1)
                           :color blue)
  ("g" goto-line "line")
  ("c" goto-char "char"))

Note that the indentation of the body argument is as if it was data and not code, i.e. the proper
one.

Incompatible changes

The macro hydra-create, as well as the variables that were supposed to be used with it
(hydra-example-text-scale, hydra-example-move-window-splitter, hydra-example-goto-error,
hydra-example-windmove) were removed. All the functionality is still there in hydra-examples.el
with the better defhydra macro.

Fixes

• amaranth heads will not call :post, since they're not quitting

New features

Keyboard quit

hydra-keyboard-quit set to "C-g" means that it's possible to quit an amaranth Hydra
with C-g. You can customize this variable.

:pre and :post refinement

:post and :pre keys can be either a single sexp or a function name. The function
doesn't need to be interactive.

Support for local Hydra heads via :bind property

Example:

(defhydra hydra-next-error (global-map "C-x")
  "next-error"
  ("`" next-error "next")
  ("j" next-error "next" :bind nil)
  ("k" previous-error "previous" :bind nil))

What it does:

• binds C-x ` to next-error.
• does not bind C-x j and C-x k
• you can still do C-x `jjkk

Thanks, @ffevotte.

Support for :bind property in Hydra body

Both body and heads recognize :bind property in their plist.
It can be either nil or a lambda of global-set-key format.

Example:

(defhydra hydra-goto (global-map "M-g"
                      :bind
                      (lambda (key cmd)
                        (bind-key key cmd)))
  ("g" goto-line "goto-line" :bind global-set-key)
  ("c" goto-char "goto-char"))

Here, global-set-key will be used to bind goto-line to M-g g. And
bind-key will be used to bind goto-char to M-g c. Note that since
bind-key is a macro, it was necessary to wrap it in a lambda.

Since this commit, it's not possible to pass a lambda instead of the whole BODY arg, as
was advertised before. Just put it on :bind now.

hydra/body will pass the initial current-prefix-arg along

Example:

(global-set-key
 (kbd "C-z")
 (defhydra hydra-vi ()
   "vi"
   ("l" forward-char)
   ("q" nil "quit")))

Now, C-u C-z l will result in (forward-char 4). All the other l
will normally call (forward-char 1), unless an additional prefix is given. The previous
behavior allowed only for C-z C-u l to get (forward-char 4).

Allow a sexp as head's CMD parameter

Example:

(defhydra hydra-launcher (:color blue)
   "Launch"
   ("h" man "man")
   ("r" (browse-url "http://www.reddit.com/r/emacs/") "reddit")
   ("w" (browse-url "http://www.emacswiki.org/") "emacswiki")
   ("s" shell "shell")
   ("q" nil "cancel"))
(global-set-key (kbd "C-c r") 'hydra-launcher/body)

Here, r and w heads are using this feature.
Here's what will be generated, if you're interested:

(defun hydra-launcher/lambda-w nil
  "Create a hydra with no body and the heads:

\"h\":    `man',
\"r\":    `(browse-url \"http://www.reddit.com/r/emacs/\")',
\"w\":    `(browse-url \"http://www.emacswiki.org/\")',
\"s\":    `shell',
\"q\":    `nil'

The body can be accessed via `hydra-launcher/body'.

Call the head: `(browse-url \"http://www.emacswiki.org/\")'."
  (interactive)
  (hydra-disable)
  (catch (quote hydra-disable)
    (call-interactively
     (function
      (lambda nil
       (interactive)
       (browse-url "http://www.emacswiki.org/"))))))

Obsolete declarations

hydra-create and all old examples in hydra-examples.el are now obsolete.
You can still use them for a short while, but they will be removed soon.

You should take the time to switch from hydra-create to defhydra. All the old examples
are provided in the new style in hydra-examples.el. However, they will not be evaluated
through (require 'hydra-examples) unless you (setq hydra-examples-verbatim t)
beforehand. This is because I have no idea what kind of bindings will work for you, you
should decide yourself. But I am providing you with a template. The number of examples
has also grown to six.

This release introduces a new color: amaranth, in addition to the previously available
red and blue.

According to Wikipedia:

The word amaranth comes from the Greek word amaranton, meaning "unwilting" (from the
verb marainesthai, meaning "wilt"). The word was applied to amaranth because it did not
soon fade and so symbolized immortality.

Hydras with amaranth body are impossible to quit with any binding except a blue head.
A check for at least one blue head exists in defhydra, so that you don't get stuck by accident.

Here's an example of an amaranth Hydra:

(global-set-key
 (kbd "C-z")
 (defhydra hydra-vi
     (:pre
      (set-cursor-color "#40e0d0")
      :post
      (set-cursor-color "#ffffff")
      :color amaranth)
   "vi"
   ("l" forward-char)
   ("h" backward-char)
   ("j" next-line)
   ("k" previous-line)
   ("e" move-end-of-line :color blue)
   ("q" nil "quit")))

The only way to exit it, is to press either q or e. No other methods will work.
You can use an amaranth Hydra instead of a red one, if for you the
cost of being able to exit only though certain bindings is less than the cost of
accidentally exiting a red Hydra by pressing the wrong prefix.

Note that it does not make sense to define a singe amaranth head, so this color can only
be assigned to the body. An amaranth body will always have some amaranth heads and some
blue heads (otherwise, it's impossible to exit), no reds.

This release adds :pre and :post statements to Hydra body, and fixes the issue with commands that want input, such as goto-line.
See the accompanying blog post for more information.

New features

This release adds the digit-argument and universal-argument machinery to Hydras. Now, each Hydra will automatically bind: 0 - 9, - and C-u. Note that digits can be used plainly, i.e. not as M-2 or C-2, but as 2.

This also means that you should try not to use the above keys as prefixes for Hydra heads.

Fixes

The heads calling hydra-disable were finally fixed for Emacs 24.4.1, thanks @bcarell.
This was hard to do, because three different Emacs versions needed three different approaches to do this.

Just a reminder:

(global-set-key
 (kbd "C-c C-v")
 (defhydra toggle (:color blue)
   "toggle"
   ("a" abbrev-mode "abbrev")
   ("d" toggle-debug-on-error "debug")
   ("f" auto-fill-mode "fill")
   ("t" toggle-truncate-lines "truncate")
   ("w" whitespace-mode "whitespace")
   ("q" nil "cancel")))

Here, all heads will call hydra-disable since they are all blue (because the body :color is blue).

Even if the body :color was red, q would still call hydra-disable, because q has nil instead of a function name.

This release introduces colorful Hydra heads. Now, each head is:

• either red - calling this head will not vanquish the Hydra. This is the default one, and
  is exactly the same as the previous behavior
• or blue - calling this head will vanquish the Hydra.

You can mix-and-match the colors, if you like.

Here's an example of a pure-blue Hydra:

(global-set-key
 (kbd "C-c C-v")
 (defhydra toggle (:color blue)
   "toggle"
   ("a" abbrev-mode "abbrev")
   ("d" toggle-debug-on-error "debug")
   ("f" auto-fill-mode "fill")
   ("t" toggle-truncate-lines "truncate")
   ("w" whitespace-mode "whitespace")
   ("q" nil "cancel")))

Here's an almost all-red Hydra, with one blue head:

(defhydra hydra-error (global-map "M-g")
  "goto-error"
  ("h" first-error "first")
  ("j" next-error "next")
  ("k" previous-error "prev")
  ("v" recenter-top-bottom "recenter")
  ("q" nil "quit"))

The q became blue, because its function is nil.
Or, for example, you could make the first head also blue:

(defhydra hydra-error (global-map "M-g")
  "goto-error"
  ("h" first-error "first" :color blue)
  ("j" next-error "next")
  ("k" previous-error "prev")
  ("v" recenter-top-bottom "recenter")
  ("q" nil "quit"))

The advantages of a pure-blue Hydra over a plain nested keymap:

• You get a hint straight away, e.g. after C-c C-v

  toggle: [a]: abbrev, [d]: debug, [f]: fill, [t]: truncate, [w]: whitespace, [q]: cancel.
  

• You can still cancel C-c C-v with any other command.