#+TITLE: Helm layer

#+TAGS: completion|layer

[[file:img/helm.png]]

* Table of Contents                     :TOC_5_gh:noexport:
- [[#description][Description]]
  - [[#features][Features:]]
- [[#install][Install]]
  - [[#alternative-layers][Alternative layers]]
- [[#configuration][Configuration]]
  - [[#auto-resize][Auto-Resize]]
  - [[#disable-helm-header][Disable Helm header]]
  - [[#define-helm-position][Define Helm position]]
  - [[#enable-fuzzy-searching-in-helm-buffers][Enable fuzzy searching in Helm buffers]]
  - [[#ripgrep-maximum-number-of-column][Ripgrep: maximum number of column]]
- [[#key-bindings][Key bindings]]
  - [[#hjkl-navigation][hjkl navigation]]
  - [[#transient-state][Transient state]]
  - [[#bookmarks][Bookmarks]]
  - [[#c-z-and-tab-switch][C-z and Tab switch]]
  - [[#helm-focus][Helm focus]]
  - [[#helm-swoop][Helm-swoop]]
  - [[#universal-argument][Universal argument]]
  - [[#replacing-text-in-several-files][Replacing text in several files]]
  - [[#resume-last-session][Resume last session]]
- [[#external-resources][External resources]]

* Description
This layer enables Helm everywhere in Spacemacs. The alternative to this
layer is the Ivy layer which brings the same level of integration as Helm.

These completion systems are the central control towers of Spacemacs, they are
used to manage buffers, projects, search results, configuration layers, toggles
and more...

Mastering your choice of completion system will make you a Spacemacs power user.

** Features:
- Project wide =grep= like text search via =helm-dir-smart-do-search=
- Project wide text replacements using =helm-edit-mode=
- Buffer wide dynamic text search via =helm-swoop=
- Fuzzy matching for most =helm-sources=
- Detailed configuration parameters for helms appearance
- Intuitive =transient state=

* Install
Helm is part of the standard distribution of Spacemacs so you don't have to do
anything to install it if you chose this distribution.

If you want/need to explicitly install Helm then add it to your =~/.spacemacs=.
You will need to add =helm= to the existing =dotspacemacs-configuration-layers=
list in this file.

** Alternative layers
Ivy layer is a replacement layer for Helm. When you add =ivy= to the existing
== list in your dotfile, it will completely replace the =helm= layer.

To switch from Ivy to Helm, modify your =~/.spacemacs=. You will need to add
=helm= to the existing =dotspacemacs-configuration-layers= list in this file,
and remove =ivy=.

* Configuration
Note: in the following configuration examples, it is possible that =helm=
is not listed explicitly in your dotfile. If that is the case then just add
it as you would with any other layers.

** Auto-Resize
It is possible to have Helm to resize its buffer window to adapt to the length
of the candidate list. By default the buffer size is fixed, to enable automatic
resizing set the layer variable =helm-enable-auto-resize= to non-nil.

#+BEGIN_SRC emacs-lisp
  (setq-default dotspacemacs-configuration-layers '(
    (helm :variables helm-enable-auto-resize t)))
#+END_SRC

Default value is =nil=.

** Disable Helm header
To hide the header in the Helm buffer set the layer variable =helm-no-header=
to non-nil.

#+BEGIN_SRC emacs-lisp
  (setq-default dotspacemacs-configuration-layers '(
    (helm :variables helm-no-header t)))
#+END_SRC

Default value is =nil=.

** Define Helm position
To set the position of the Helm buffer add the layer variable =helm-position=
to your dotfile.

The supported values are =bottom=, =top=, =left= and =right=.

#+BEGIN_SRC emacs-lisp
  (setq-default dotspacemacs-configuration-layers '(
    (helm :variables helm-position 'top)))
#+END_SRC

Default value is =bottom=.

** Enable fuzzy searching in Helm buffers
It is possible to control the fuzziness of Helm when searching for candidates.
By default this layer /tries/ to enable fuzzy search to all Helm sources.
You can limit the fuzzy search to helm own defaults by setting the layer
variable =helm-use-fuzzy= to the value ='source=.

#+BEGIN_SRC emacs-lisp
  (setq-default dotspacemacs-configuration-layers '(
    (helm :variables helm-use-fuzzy 'source)))
#+END_SRC

Default value is =always=.

** Ripgrep: maximum number of column
If you use =ripgrep= the default value for =--max-columns= is =512=. To change
if set the layer variable =spacemacs-helm-rg-max-column-number=.

#+BEGIN_SRC emacs-lisp
  (setq-default dotspacemacs-configuration-layers '(
    (helm :variables spacemacs-helm-rg-max-column-number 1024)))
#+END_SRC

* Key bindings
** hjkl navigation
When using the Vim style or Hybrid style with the variable
=hybrid-style-enable-hjkl-bindings= set to =t=, Spacemacs adds navigation in the
Helm buffers with ~hjkl~.

| Key binding | Description                  |
|-------------+------------------------------|
| ~C-h~       | go to next source            |
| ~C-H~       | describe key (replace ~C-h~) |
| ~C-j~       | go to previous candidate     |
| ~C-k~       | go to next candidate         |
| ~C-l~       | same as ~return~             |

** Transient state
Spacemacs defines a transient state for =Helm= to make it work like [[https://github.com/Shougo/unite.vim][Vim's Unite]]
plugin.

Initiate the transient state with ~M-SPC~ or ~s-M-SPC~ while in a =Helm= buffer.

| Key binding          | Description                                          |
|----------------------+------------------------------------------------------|
| ~M-SPC~ or ~s-M-SPC~ | initiate the transient state                         |
| ~q~                  | quit transient state                                 |
| ~TAB~                | switch to actions page and leave the transient state |
| ~1~                  | execute action 0                                     |
| ~2~                  | execute action 1                                     |
| ~3~                  | execute action 2                                     |
| ~4~                  | execute action 3                                     |
| ~5~                  | execute action 4                                     |
| ~6~                  | execute action 5                                     |
| ~7~                  | execute action 6                                     |
| ~8~                  | execute action 7                                     |
| ~9~                  | execute action 8                                     |
| ~0~                  | execute action 9                                     |
| ~a~                  | switch to actions page                               |
| ~g~                  | go to first candidate                                |
| ~G~                  | go to last candidate                                 |
| ~h~                  | go to previous source                                |
| ~j~                  | select next candidate                                |
| ~k~                  | select previous candidate                            |
| ~l~                  | go to next source                                    |
| ~t~                  | mark current candidate                               |
| ~T~                  | mark all candidates                                  |
| ~v~                  | execute persistent action                            |

** Bookmarks
In the =helm-bookmarks= buffer:

| Key binding | Description                                  |
|-------------+----------------------------------------------|
| ~C-d~       | delete the selected bookmark                 |
| ~C-e~       | edit the selected bookmark                   |
| ~C-f~       | toggle filename location                     |
| ~C-o~       | open the selected bookmark in another window |

** C-z and Tab switch
The command bound to ~C-z~ is much more useful than the one bound to Tab, so it
makes sense to swap them. It's also recommended [[http://tuhdo.github.io/helm-intro.html][here]].

** Helm focus
If you find yourself unable to return focus to Helm (after a careless
mouse-click for example), use ~SPC w b~ to return focus to the minibuffer.

** Helm-swoop
[[https://github.com/ShingoFukuyama/helm-swoop][Helm-swoop]] is very similar to =moccur=, it displays a =helm= buffer with all the
occurrences of the word under point. You can then change the search query in
real-time and navigate between them easily.

You can even edit the occurrences directly in the =helm= buffer and apply the
modifications to the buffer.

| Key binding | Description                    |
|-------------+--------------------------------|
| ~SPC s C~   | clear =helm-swoop= own cache   |
| ~SPC s s~   | execute =helm-swoop=           |
| ~SPC s S~   | execute =helm-multi-swoop=     |
| ~SPC s C-s~ | execute =helm-multi-swoop-all= |

** Universal argument
~SPC u~ is not working before =helm-M-x= (~SPC SPC~). Instead, call =helm-M-x=
first, select the command you want to run, and press ~C-u~ before pressing
~RETURN~. For instance: ~SPC SPC org-reload C-u RET~

** Replacing text in several files
If you have =rg=, =ag=, =pt= or =ack= installed, replacing an occurrence of text
in several files can be performed via [[https://github.com/syohex/emacs-helm-ag][helm-ag]].

Say you want to replace all =foo= occurrences by =bar= in your current
project:
- initiate a search with ~SPC /~
- enter in edit mode with ~C-c C-e~
- go to the occurrence and enter in =iedit state= with ~SPC s e~
- edit the occurrences then leave the =iedit state=
- press ~C-c C-c~

*Note*: In Spacemacs, =helm-ag= despite its name works with =rg=, =pt= and =ack=
as well (but not with =grep=).

** Resume last session
Use ~SPC r l~ to resume the last helm session. For instance it is handy to
quickly toggle on and off a toggle using ~SPC h t~.

* External resources
- [[https://github.com/emacs-helm/helm/wiki][The Helm wiki]]
- [[http://tuhdo.github.io/helm-intro.html][The Helm guide]]