• State of Development
• Quick Feature Overview
  • Fancy Gifs!
• Quick Start
• Detailed Feature List
  • Projects and Workspaces
  • Conveniently Editing Your Projects and Workspaces
  • Navigation without Projects and Workspaces
  • Frame Locality
  • Mouse Interface
  • Follow-mode
  • Tag-follow-mode
  • Fringe-indicator-mode
  • Git-mode
  • Filewatch-mode
  • File Management
  • Indent-guide-mode
  • Git-commit-diff-mode
  • Session Persistence
  • Terminal Compatibility
  • Tag View
  • Current-Directory Awareness
  • Tramp Support
  • Org Support
  • Theme Support
  • Peeking
  • Additional Packages
  • Treemacs as a Framework
• Installation
• Configuration
  • Variables
  • Faces
  • Evil compatibility
  • Customizing Themes and Icons
• Keymap
  • Unbound functions
  • Default keymaps
• Compatibility
• FAQ
• Contributing
• Working With The Code Base
• Dependencies

Treemacs is currently in an active - but low intensity - state of development. New features are worked on, PRs will be looked at and issues answered - eventually. My time budget is limited, so looking for new work just means looking at whatever is currently at the top of my inbox. If you feel like the ticket you’ve opened has gone unanswered for a while feel free to give it a bump - you are explicitly encouraged to do so.

Treemacs is a file and project explorer similar to NeoTree or vim’s NerdTree, but largely inspired by the Project Explorer in Eclipse. It shows the file system outlines of your projects in a simple tree layout allowing quick navigation and exploration, while also possessing basic file management utilities. Specifically a quick feature overview looks as follows:

Project management

Treemacs lets you view multiple file trees - projects - at once and quickly add or remove them, and groups projects in workspaces.

Easy navigation

quickly move between projects or use shortcuts to jump to parent or neighbouring nodes.

Versatile file access

decide exactly how and where a file will be opened, including using ace-window to choose a window or launching an external application.

Understanding of frames

every frame will receive its own treemacs buffer that will live and die with that frame.

Finding of files and tags

Treemacs can follow along and keep in focus the currently selected file or even the tag at point, either manually or automatically using either treemacs-follow-mode or treemacs-tag-follow-mode.

Git Integration

Treemacs can use different faces for files and directories based on their git status. The git process is run asynchronously, minimizing its performance impact.

Winum & ace-window compatibility

The presence of treemacs will not interfere with winum’s and ace-window’s usual layouts.

Projectile/project.el integration

the treemacs-projectile package lets you quickly add your projectile projects to the treemacs workspace. project.el compatibility is built-in.

Simple mouse interface

Left clicks will work the same as you’re used to from with graphical applications

Session persistence

Treemacs automatically saves and restores your workspaces.

Dashing good looks

Treemacs uses (optionally resizable) png images in HD 22x22 resolution for its icons. When run in a terminal a simple fallback is used.

Tag view

Treemacs can display files’ tags. All file types that Emacs can generate a (semantic) imenu index for are supported.

Visual feedback

When it would otherwise be difficult to see the message in the minibuffer success/failure is indicated with pulse.el.

Theming support

Treemacs supports using multiple icon themes that can be changed at will.

Ease of use

Treemacs offers many configuration options, but comes with a set of (what hopefully should be) sane defaults. Installation aside there are two obligatory pieces of setup: 1) Choosing convenient keybindings to run treemacs and 2) If you use evil: requiring treemacs-evil to integrate treemacs with evil and enable j/k navigation. More on both below. You can also summon helpful hydras with ? and C-? that will remind you of treemacs’ many keybindings and features.

Bookmark integration

Running bookmark-set on a Treemacs item will store a bookmark to Treemacs buffer for that item.

(The font used in the gifs is Fantasque Sans Mono)

Various ways to open files:

Workspace administration with org-mode:

Automatic reaction to changes in the file system:

Automatic reaction to changes in git:

Full-featured mouse interface:

Including moving and opening files via mouse drag:

Resizable icons:

If you don’t care about reading the full readme here’s a list of some bare bones basics to get you started:

• First of all: press ? to summon the helpful hydra:
• If you use evil don’t forget to also install treemacs-evil
• If you use projectile you can install treemacs-projectile to allow quickly add your projectile projects to treemacs.
• Treemacs doesn’t bind any global keys, you need to use whatever fits you best. A full install setup can be found below. Otherwise just add a keybind for treemacs.
• For navigation use n/p (j/k when evil), M-n/M-p to move to same-height neighbour, u to go to parent, and C-j/C-k to move between projects.
• There’s half a dozen different ways to open nodes, all bound under o as prefix. Pick your favourite.
• TAB and RET are particularly configurable. See treemacs-TAB/RET-actions-config.
• Projects administration is bound under the C-c C-p prefix.

If you’ve previously used a different explorer like NeoTree or NerdTree - or an earlier version of treemacs for that matter - you are probably used to a display system wherein you see exactly a single file tree whose exact root you can arbitrarily change. This system makes it difficult to work on and switch between multiple projects. Treemacs used to (and still does) remedy that limitation by making every treemacs buffer unique to its frame, but it has now been redesigned to be able to display multiple file trees - projects - at once.

In treemacs a workspace is simply a (named) collection of projects, while a project mostly consists of 2 things: its location in the file system and its name. This is the info that you need to provide when you want to add a new project to your workspace. Just like projects you can add, remove, rename and switch between workspaces at any time.

This design approach has various advantages and disadvantages. It is now no longer possible to “free roam” in the file system with treemacs, i.e. you can no longer arbitrarily switch the single file tree’s root to the directory at point or the current root’s parent. Another restriction is that the same part of the file system may not appear more than once as part of the workspace. For example, it is not possible to have both /Documents and /Documents/ProjectX as projects in the same workspace, since internally treemacs heavily relies on every node having a unique natural key in its absolute path. Nonetheless the pros certainly outweigh the cons, as a multiroot setup allows to work on multiple projects with any combination concern/buffer separating frameworks, be it persp/perspective, eyebrowse, tab-bar-mode, or project.el/projectile. It also opens the potential for concurrent display not only of the file system, but e.g. the currently open buffers.

When a workspace is first needed, treemacs will select a workspace in the following manner:

If the current buffer is editing a file then treemacs will try to find the first workspace with a project containing that file. If that fails treemacs will resort to using the fallback workspace which is defined as simply the first element in the list of all workspace.

The order of workspaces is the same that you see when calling treemacs-edit-workspaces (see next chapter). You can interactively set the fallback workspace by calling treemacs-set-fallback-workspace.

This selection will happen when treemacs is first started (with a command like treemacs-select-window) or when a function that requires the current workspace to be known is used (like adding or removing a project).

It is possible to disable a workspace or project so it won’t appear in treemacs, but still remains a part of your loadout, keeping it visible when you go edit your workspaces. To do so simply start the name of the workspace or project with “COMMENT”:

There are two ways to edit your projects and workspaces: call up single add/remove/rename/switch commands under either the C-c C-p or C-c C-w prefix, or call treemacs-edit-workspaces and edit your entire layout in the form of a single org-mode buffer.

The used org-format is quite simple: level 1 headlines are names of workspaces, level 2 headlines are names of projects in a workspace, and every project’s path is given as a description list, starting with a - (and an optional leading space). Empty lines and lines starting with # are ignored, and everything else leads to an error.

You needn’t worry about making mistakes either. If there’s something wrong when you call treemacs-finish-edit (C-c C-c) then treemacs will point you at the incorrect line and tell you what’s missing:

(Note that the list with the path property allows an indentation of 0 or 1 spaces only. The much greater visible indentation is caused by org-indent-mode)

If a strict workspace and project structure, as described above, is too stringent for your use-case there are multiple other ways to use treemacs in a more “free-form” style:

• You can use treemacs-display-current-project-exclusively to display only the current project (removing all other projects from the workspace).
• You can enable treemacs-project-follow-mode to make treemacs automatically switch to the project for the current buffer.
• As long as there is exactly a single project in your workspace you can also use M-H and M-L (or treemacs-root-up and treemacs-root-down) to arbitrarily change the project’s root and freely navigate through your your file system, similar to dired. M-H will navigate one level upward in the file system, M-L will move into the directory at point.

Treemacs buffers have a limited scope they are visible in: the frames they are created in. A treemacs buffer, once created, lives alongside and inside its frame, and is also destroyed with that frame. Calling treemacs while inside a new frame will create a new buffer for it, regardless how many other treemacs buffers already exist. While there can be multiple unique treemacs buffer they will all still show the same workspace and the same projects.

A treemacs buffer that does not belong to a frame may still be made visible by manually selecting in the buffer list. This would break various assumptions in treemacs’ code base and effectively falls under undefined behaviour - a bad idea all around.

Treemacs handles left clicks in much the same way as modern graphical applications do: a single click sets the focus, a double click expands or collapses a directory or tag section node and visits a file/moves to a tag for a file/tag node.

Additionally tag sections can be expanded or collapsed by a single click on the file/tag section icon.

If you prefer to expand/collapse nodes with a single mouse click you can also use treemacs-single-click-expand-action:

(with-eval-after-load 'treemacs
  (define-key treemacs-mode-map [mouse-1] #'treemacs-single-click-expand-action))

A right click popup-menu is also available:

You can move and open files by dragging them with the mouse.

treemacs-follow-mode is a global minor mode which allows the treemacs view to always move its focus to the currently selected file. This mode runs on an idle timer - the exact duration of inactivity (in seconds) before a move is called is determined by treemacs-tag-follow-delay.

treemacs-tag-follow-mode is a global minor mode which extends and effectively replaces treemacs-follow-mode. When activated it follows not just the current file, but also the current tag. This works alongside treemacs’ integration with imenu, so all file types providing an imenu implementation are compatible.

This mode, like follow-mode, runs on an idle timer - the exact duration of inactivity (in seconds) before a move is called is determined by treemacs-tag-follow-delay.

Note that in order to move to a tag in treemacs the treemacs buffer’s window needs to be temporarily selected, which will reset blink-cursor-mode’s timer if it is enabled. This will result in the cursor blinking seemingly pausing for a short time and giving the appearance of the tag follow action lasting much longer than it really does.

treemacs-fringe-indicator-mode is a global minor mode that displays a little icon in the fringe that moves with the cursor. It can make the selected line more visible if hl-line-mode doesn’t stand out with your theme.

The indicator can either be permanently visible, or be only shown when the treemacs window is selected by calling it either with the always or only-when-focused argument.

treemacs-git-mode is a global minor mode which enables treemacs to check for files’ and directories’ git status information and highlight them accordingly (see also the treemacs-git-... faces). The mode is available in 3 variants: simple, extended and deferred:

• The simple variant starts a git status process and parses its output in elisp. The parsing is kept quick and simple, so some info is missed: this version includes git status information only for files, but not directories.
• The extended variant highlights both files and directories. This greatly increases the complexity and length of the parsing process, and is therefore done in an asynchronous python process for the sake of performance. The extended variant requires python3 to work.
• The deferred variant is the same as extended, except the tasks of rendering nodes and highlighting them are separated. The former happens immediately, the latter after treemacs-deferred-git-apply-delay seconds of idle time. This may be faster (if not in truth then at least in appereance) as the git process is given a much greater amount of time to finish. The downside is that the effect of nodes changing their colors may be somewhat jarring, though this effect is largely mitigated due to the use of a caching layer.

When called interactively treemacs-git-mode will ask for the variant to use. In lisp code an appropriate symbol can be directly passed to the minor mode function:

(treemacs-git-mode 'deferred)

All versions use an asynchronous git process and are optimized to not do more work than necessary, so their performance cost should, for the most part, be the constant amount of time it takes to fork a subprocess. For repositories where this is not the case treemacs-max-git-entries (default value 5000) will limit the number of git status entries treemacs will process before ignoring the rest.

treemacs-filewatch-mode is a global minor mode which enables treemacs to watch the files it is displaying for changes and automatically refresh itself when it detects a change in the file system that it decides is relevant.

A change event is relevant for treemacs if a new file has been created or deleted or a file has been changed and treemacs-git-mode is enabled. Events caused by files that are ignored as per treemacs-ignored-file-predicates are likewise counted as not relevant.

The refresh is not called immediately after an event was received, treemacs instead waits treemacs-file-event-delay ms to see if any more files have changed to avoid having to refresh multiple times over a short period of time. Treemacs will not refresh the entire view to make the detected changes visible, but will instead only make updates to the directories where the change(s) happened. Using this mode is therefore by far not as expensive as a full refresh on every change and save.

The mode only applies to directories opened after this mode has been activated. This means that to enable file watching in an already existing treemacs buffer it needs to be killed and rebuilt. Turning off this mode is, on the other hand, instantaneous - it will immediately turn off all existing file watch processes and outstanding refresh actions.

Known limitations:

• Staging and committing changes does not produce any file change events of its own, if you use treemacs-git-mode you still need to do a manual refresh to see your files’ faces go from ‘changed’ and ‘untracked’ to ‘unchanged’ after a commit. The treemacs-magit package provides the necessary hooks to fill this gap.
• Filewatch-mode may not be able to track file modifications on MacOS, making git-mode miss potential changes, see also this comment.

Treemacs is no dired, but it supports the basic file management facilities of creating, deleting, moving, copying and renaming files.

It is also possible to mark multiple files to act on them. M-m will summon a hydra for bulk file actions. NOTE: The bulk action implementation is using treemacs’ (yet to be documented) annotation api, which is set up to provide permanent annotations like colouring based on flycheck’s error/warning/info output. This means that marking files will likewise be permanent, even if you collapse the directories containing those files and they are no longer visible.

treemacs-indent-guide-mode is a simple visual helper based on the options provided by the treemacs-indentation and treemacs-indentation-string settings. Its appearance is dictated by treemacs-indent-guide-style, the options are either line:

or block:

treemacs-git-commit-diff-mode will annotate git-tracked project to show how many commits the local repo is ahead or behind its remote counterpart:

Treemacs’ sessions - your workspace and the projects it contains - are saved when Emacs shuts down and restored when treemacs is first loaded. This persistence process is fully automatic and independent, and should therefore be fully compatible with desktop-save-mode.

The persisted state is saved under user-emacs-directory/.cache/treemacs-persist by default. The exact file location is saved in the variable treemacs-persist-file.

If something goes wrong when loading the file the erroneous state will be saved in treemacs-last-error-persist-file for debugging.

When run in a terminal treemacs will fall back to a much simpler rendering system, foregoing its usual png icons and using simple + and - characters instead. The exact characters used are highly customizable.

Treemacs is able to display not only the file system, but also tags found in individual files. The tags list is sourced using emacs’ builtin imenu functionality, so all file types that emacs can generate an imenu index for are supported.

Imenu caches its result, so to avoid stale tag lists setting imenu-auto-rescan to t is recommended. Tags generated with the help of semantic-mode are likewise supported.

Treemacs can show the tags produced by ggtags if you switch a buffer’s imenu index function to use ggtags:

(setq-local imenu-create-index-function #'ggtags-build-imenu-index)

Treemacs always sets the default-directory variable based on the (nearest) path at the current node, falling back to your home directory when there is no node or path at point. That means that various commands like find-file, ediff magit-status or helm-projectile-ag will correctly act based on the current directory or project context.

Treemacs supports projects on remote directories, e.g. /scp:remote-server:path/to/directory.

However tramp support has some restrictions: treemacs-use-collapsed-directories has no effect on remote directories.

Treemacs supports storing links to its file nodes by means of org-store-link.

Using a different treemacs theme works the same way as using a different Emacs theme: just call treemacs-load-theme, either programmatically or interactively. In the former case you need to supply the name of the theme as a string, like this:

(treemacs-load-theme "Default")

Do keep in mind that by default treemacs’ theme support is all theory: the standard installation includes only the default theme; this feature is meant to easily allow others to extend, create and distribute themes for treemacs.

A detailed explanation on modifying themes and icons can be found in the Configuration section.

If you want to look at files from within treemacs, without opening them with RET and switching to another window, you can do so with P which activates treemacs-peek-mode. When peek-mode is active treemacs will automatically preview the file at point.

To quit peek-mode either press P again to disable it or open a file with RET. Either way upon exiting peek-mode all files that have been opened due to peeking will be closed again (with the exception of the one that you opened with RET, of course).

You can scroll the window being peeked (and in general other-window when you are in treemacs) with M-N/P or M-J/K if you use treemacs-evil.

Next to treemacs itself you can optionally install:

Must be installed and loaded if you use evil. The keybindings and the cursor will not be setup properly otherwise. It’ll also enable navigation with j/k instead of n/p.

Allows to quickly add your projectile projects to the treemacs workspace.

A small utility package to fill the small gaps left by using filewatch-mode and git-mode in conjunction with magit: it will inform treemacs about (un)staging of files and commits happening in magit.

Allows you to use treemacs icons in dired buffers with treemacs-icons-dired-mode:

Integration with persp-mode or perspective.el that allows treemacs buffers to be unique inside the active perspective instead of the default frame-based buffer scope.

Integration with tab-bar-mode that allows treemacs buffers to be unique inside the active tab instead of the default frame-based buffer scope.

Provides a theme using all-the-icons.

Treemacs can be extended to display arbitrary nodes as well as be used as a general rendering backend for any tree-like structures. See here for an extended tutorial and demonstration.

Treemacs is included in Spacemacs (for now only on the dev branch). If you are using the development version of Spacemacs you can simply add treemacs to dotspacemacs-configuration-layers to replace the default NeoTree. Check SPC h SPC treemacs for details. Otherwise you will need to add treemacs to dotspacemacs-additional-packages.

Treemacs is also available on MELPA. If you just want to quickly start using it grab the use-package example below, and customize it as needed (remove treemacs-evil if you don’t use it, customize the keybindings to you taste, etc).

Either way keep in mind that treemacs has no default keybindings for its globally callable initialization functions. Each user is supposed to select keybindings for functions like treemacs-find-file based on whatever they find convenient.

You can find an exhaustive overview of all functions, their keybindings and functions you need to bind yourself below.

The following use-package snippet includes a list of all of treemacs’ configuration options in their default setting. Setting them, or activating the minor modes yourself is not necessary, they are only listed here to encourage discoverability.

(use-package treemacs
  :ensure t
  :defer t
  :init
  (with-eval-after-load 'winum
    (define-key winum-keymap (kbd "M-0") #'treemacs-select-window))
  :config
  (progn
    (setq treemacs-collapse-dirs                   (if treemacs-python-executable 3 0)
          treemacs-deferred-git-apply-delay        0.5
          treemacs-directory-name-transformer      #'identity
          treemacs-display-in-side-window          t
          treemacs-eldoc-display                   'simple
          treemacs-file-event-delay                2000
          treemacs-file-extension-regex            treemacs-last-period-regex-value
          treemacs-file-follow-delay               0.2
          treemacs-file-name-transformer           #'identity
          treemacs-follow-after-init               t
          treemacs-expand-after-init               t
          treemacs-find-workspace-method           'find-for-file-or-pick-first
          treemacs-git-command-pipe                ""
          treemacs-goto-tag-strategy               'refetch-index
          treemacs-header-scroll-indicators        '(nil . "^^^^^^")
          treemacs-hide-dot-git-directory          t
          treemacs-indentation                     2
          treemacs-indentation-string              " "
          treemacs-is-never-other-window           nil
          treemacs-max-git-entries                 5000
          treemacs-missing-project-action          'ask
          treemacs-move-forward-on-expand          nil
          treemacs-no-png-images                   nil
          treemacs-no-delete-other-windows         t
          treemacs-project-follow-cleanup          nil
          treemacs-persist-file                    (expand-file-name ".cache/treemacs-persist" user-emacs-directory)
          treemacs-position                        'left
          treemacs-read-string-input               'from-child-frame
          treemacs-recenter-distance               0.1
          treemacs-recenter-after-file-follow      nil
          treemacs-recenter-after-tag-follow       nil
          treemacs-recenter-after-project-jump     'always
          treemacs-recenter-after-project-expand   'on-distance
          treemacs-litter-directories              '("/node_modules" "/.venv" "/.cask")
          treemacs-project-follow-into-home        nil
          treemacs-show-cursor                     nil
          treemacs-show-hidden-files               t
          treemacs-silent-filewatch                nil
          treemacs-silent-refresh                  nil
          treemacs-sorting                         'alphabetic-asc
          treemacs-select-when-already-in-treemacs 'move-back
          treemacs-space-between-root-nodes        t
          treemacs-tag-follow-cleanup              t
          treemacs-tag-follow-delay                1.5
          treemacs-text-scale                      nil
          treemacs-user-mode-line-format           nil
          treemacs-user-header-line-format         nil
          treemacs-wide-toggle-width               70
          treemacs-width                           35
          treemacs-width-increment                 1
          treemacs-width-is-initially-locked       t
          treemacs-workspace-switch-cleanup        nil)

    ;; The default width and height of the icons is 22 pixels. If you are
    ;; using a Hi-DPI display, uncomment this to double the icon size.
    ;;(treemacs-resize-icons 44)

    (treemacs-follow-mode t)
    (treemacs-filewatch-mode t)
    (treemacs-fringe-indicator-mode 'always)
    (when treemacs-python-executable
      (treemacs-git-commit-diff-mode t))

    (pcase (cons (not (null (executable-find "git")))
                 (not (null treemacs-python-executable)))
      (`(t . t)
       (treemacs-git-mode 'deferred))
      (`(t . _)
       (treemacs-git-mode 'simple)))

    (treemacs-hide-gitignored-files-mode nil))
  :bind
  (:map global-map
        ("M-0"       . treemacs-select-window)
        ("C-x t 1"   . treemacs-delete-other-windows)
        ("C-x t t"   . treemacs)
        ("C-x t d"   . treemacs-select-directory)
        ("C-x t B"   . treemacs-bookmark)
        ("C-x t C-t" . treemacs-find-file)
        ("C-x t M-t" . treemacs-find-tag)))

(use-package treemacs-evil
  :after (treemacs evil)
  :ensure t)

(use-package treemacs-projectile
  :after (treemacs projectile)
  :ensure t)

(use-package treemacs-icons-dired
  :hook (dired-mode . treemacs-icons-dired-enable-once)
  :ensure t)

(use-package treemacs-magit
  :after (treemacs magit)
  :ensure t)

(use-package treemacs-persp ;;treemacs-perspective if you use perspective.el vs. persp-mode
  :after (treemacs persp-mode) ;;or perspective vs. persp-mode
  :ensure t
  :config (treemacs-set-scope-type 'Perspectives))

(use-package treemacs-tab-bar ;;treemacs-tab-bar if you use tab-bar-mode
  :after (treemacs)
  :ensure t
  :config (treemacs-set-scope-type 'Tabs))

Treemacs offers the following configuration options (describe-variable will usually offers more details):

Treemacs defines and uses the following faces:

To make treemacs get along with evil-mode you need to install and load treemacs-evil. It does not define any functions or offer any configuration options, making sure it is loaded is sufficient.

Creating and modifying themes and icons is all done in a single step using dedicated macros.

To create a theme use treemacs-create-theme. It requires the name of the theme and accepts 3 optional keyword arguments: the directory the theme’s icons are stored in (if it’s using png icons), the name of the theme it’s extending and the config, a final form that’s responsible for creating all the theme’s icons. A config will typically consist of nothing but calls to treemacs-create-icon:

(treemacs-create-theme "Default"
  :icon-directory (treemacs-join-path treemacs-dir "icons/default")
  :config
  (progn
    (treemacs-create-icon :file "root-open.png"   :fallback ""       :extensions (root-open))
    (treemacs-create-icon :file "root-closed.png" :fallback ""       :extensions (root-closed))
    (treemacs-create-icon :file "emacs.png"       :fallback "🗏 "     :extensions ("el" "elc"))
    (treemacs-create-icon :file "readme.png"      :fallback "🗏 "     :extensions ("readme.md"))
    (treemacs-create-icon :icon (all-the-icons-icon-for-file "yaml") :extensions ("yml" "yaml"))))

The :file argument is relative to the icon directory of the theme being created. When not using image icons the :icon-directory argument can be omitted and the :file argument can be switched for :icon to supply the icon string directly. The TUI fallback is also optional, ” ” is used by default. Finally the list of extensions determines which file extensions the icon should be used for.

For treemacs an extension is either the entire file name or the text after the last period (unless treemacs-file-extension-regex is customized). This means it can match normal file names like “init.el”, extensionless file names like “Makefile”. Because the full name is checked first it is possible to give special files their own icon, for example “Readme.md” can use a different icon than normal markdown files.

Instead of a string extension a symbol can also be used. In this case treemacs will also create a variable for that icon named treemacs-icon-$symbol. Treemacs uses several such icon variables and any new theme should define their own versions (it’s not extending the default theme). The following icons are used:

• root-open
• root-closed
• dir-closed
• dir-open
• fallback
• tag-open
• tag-closed
• tag-leaf
• error
• info
• warning

Analogous to creating a new theme treemacs-modify-theme can be used to change, or add to, an existing theme:

(treemacs-modify-theme "Default"
  :icon-directory "/other/icons/dir"
  :config
  (progn
    (treemacs-create-icon :icon "+" :extensions (dir-closed))
    (treemacs-create-icon :icon "-" :extensions (dir-open))))

Finally keep in mind that treemacs’ icons are all buffer-local values, and will most likely not be defined when trying to access their values directly. When you need to programmatically access some of treemacs’ icons you should use treemacs-get-icon-value:

(treemacs-get-icon-value 'root-closed nil "Default")
(treemacs-get-icon-value "org" t)

Treemacs also offers a quick and straighforward way to add a (gui) icon to the currently active theme, without caring for its name or declaring icon directories:

(defvar treemacs-custom-html-icon (all-the-icons-icon-for-file "name.html"))
(treemacs-define-custom-icon treemacs-custom-html-icon "html" "htm")

Important: There is a restriction that all icons must must be exactly 2 characters long. That’s including the space that will separate an icon from the filename.

If you want to create an icon based on an image you can use treemacs-define-custom-image-icon instead:

(treemacs-define-custom-image-icon "/path/to/icon.png" "htm" "html")

For icons of directories two icon variants are needed: one for an open and one for a closed directory state. These can be indicated with a simple "-open" and "-closed" suffix. For example the following lines will add special icons for directories named “scripts”:

(treemacs-define-custom-icon "X " "scripts-closed")
(treemacs-define-custom-icon "Y " "scripts-open")

For some file extensions, like “.cc” or “.hh”, it is not immediately obvious which major mode will open these files, and thus which icon they should be assigned. Treemacs offers the option that automate this decision based on auto-mode-alist. You can use the function treemacs-map-icons-with-auto-mode-alist to change the assigned icons for a list of file extensions based on the major mode the icons are mapped to in auto-mode-alist.

treemacs-map-icons-with-auto-mode-alist takes 2 arguments: first a list of file extensions, then an alist that decides which icon should be used for which mapped major mode. For example, the code to decide the icons for “.hh” and “.cc” files with auto-mode-alist would look like this:

(treemacs-map-icons-with-auto-mode-alist
 '(".cc" ".hh")
 `((c-mode   . ,(treemacs-get-icon-value "c"))
   (c++-mode . ,(treemacs-get-icon-value "cpp"))))

It is possible to force treemacs to use the simple TUI icons in GUI mode by setting treemacs-no-png-images to t.

If your emacs has been compiled with Imagemagick support, or you’re using Emacs >= 27.1, you can arbitrarily change the size of treemacs’ icons by (interactively or programmatically) calling treemacs-resize-icons.

Depending on your font you may experience the problem of treemacs’ icons seemingly jumping around left and right when they are expanded and collapsed when using the all-the-icons theme. The straighforward solution is to use a different font. You may also try a workaround of using a different font that applies only to the TAB characters used to align treemacs’ all-the-icons-based icons. To do that do not load treemacs-all-the-icons with require. Instead use the following alternative provided by treemacs itself:

(treemacs-load-all-the-icons-with-workaround-font "Hermit")

The Hermit font used here is just an example - you will need to pick a font that is available on your system and does not suffer from the tab width issue.

This line will load treemacs-all-the-icons (it must not have been loaded previously) and enable the all-the-icons theme. The given font argument will be used as the font for the alignment tabs used for the icons, hopefully alleviating the indentation problem. In addition treemacs-indentation and treemacs-indentation-string will be set to 1 and a (font-changed) TAB character respectively, so customizing them is (probably) not possible.

These functions are not bound to any keys by default. It’s left up to users to find the most convenient key binds.

Treemacs’ keybindings are distributed to several keymaps, based on common keybindings:

The correctness of treemacs’ display behaviour is, to a large degree, ensured through window properties and reacting to changes in the window configuration. The packages most likely to cause trouble for treemacs are therefore those that interfere with Emacs’ buffer spawning and window splitting behaviour. Treemacs is included in Spacemacs and I am a Spacemacs user, therefore treemacs guarantees first-class support & compatibility for window-managing packages used in Spacemacs, namely persp/perspective, eyebrowse, popwin and window-purpose, as well as shackle. For everything else there may be issues and, depending on the complexity of the problem, I may decide it is not worth fixing.

Aside from this there are the following known incompatibilities:

• Any package invoking font-lock-ensure in the treemacs buffer. This will reset the faces of treemacs’ buttons (once) and is a known emacs bug.
• A possible cause of this issue using an old version of swiper.
• Rainbow mode activated in treemacs will likewise produce this behaviour. Make sure not to include rainbow-mode as part of special-mode-hook, since this is the mode treemacs-mode is derived from.

• I don’t need multiple projects, can treemacs just always show me the current project I’m in?

  Yes, see the section about Navigation without Projects and Workspace.

• How do I hide files I don’t want to see?

  You need to define a predicate function and add it to treemacs-ignored-file-predicates. This function accepts two arguments, a file’s name and its absolute path, and must return non-nil when treemacs should hide that file.

  For example, the code to ignore files either called “foo” or located in ”x/y/z” would look like this:

  (with-eval-after-load 'treemacs
  
    (defun treemacs-ignore-example (filename absolute-path)
      (or (string-equal filename "foo")
          (string-prefix-p "/x/y/z/" absolute-path)))
  
    (add-to-list 'treemacs-ignored-file-predicates #'treemacs-ignore-example))
      

• How do I keep treemacs from showing files that are ignored by git?

  You can use treemacs-hide-gitignored-files-mode (bound to ti) to switch between hiding and displaying of gitignored files. Git-mode must be enabled for this feature to work.

• Why am I seeing no file icons and only +/- for directories?

  Treemacs will permanently fall back on its simple TUI icons if it detects that the emacs instance it is run in cannot create images. You can test this by evaluating (create-image "" 'png). If this code returns an error like “Invalid image type ´png´” your emacs does not support images.

• How do I get treemacs to stop telling me when it’s been refreshed, especially with filewatch-mode?

  See treemacs-silent-refresh and treemacs-silent-filewatch.

• ENOSPC / No space left on device / no file descriptor left

  You may run into this error when you use filewatch-mode. The solution is to increase the number of allowed user watches, as described here for Linux and here for Mac.

  You will also want to see what’s responsible for setting all those file watches in the first place, since treemacs only watches the expanded directories it is displaying and so won’t produce more than a couple dozen watches at best.

• Why is treemacs warning me about not being able to find some background colors and falling back to something else?

  Treemacs needs those colors to make sure that background colors of its icons correctly align with hl-line-mode. Png images’ backgrounds are not highlighted by hl-line-mode by default, treemacs is manually correcting this every time hl-line’s overlay is moved. To make that correction work it needs to know two colors: the current theme’s default background, and its hl-line background color. If treemacs cannot find hl-lines’s background color it falls back to the default background color. If it cannot even find the default background it will fall back to #2d2d31. The warnings serve to inform you of that fallback.

  If your theme does not define a required color you can set it yourself before treemacs loads like this:

  (set-face-attribute 'hl-line nil :background "#333333")
      

  If you just want to disable the warnings you can do so by defining the variable treemacs-no-load-time-warnings. Its exact value is irrelevant, all that matters is that it exists at all. Since the warnings are issues when treemacs is first being loaded the variable must be defined before treemacs is initialized. This is best achieved by adding the line (defvar treemacs-no-load-time-warnings t) to treemacs’ use-package :init block.

• Can I expand everything under a node?

  Yes, you just need to expand it with a prefix argument. Closing nodes with a prefix argument works as well. In this case treemacs will forget about the nodes opened below the one that was closed and not reopen them automatically.

• Broken display of CJK characters

  If you are seeing raw bytes like \316 instead of proper CJK characters like in this issue you have to set the proper language environment, e.g.:

  (set-language-environment 'Chinese-GB18030)
      

Contributions are very much welcome, but should fit the general scope and style of treemacs. The following is a list of guidelines that should be met (exceptions confirm the rule):

• There should be one commit per feature.
• Commit messages should start with a note in brackets that roughly describes the area the commit relates to, for example [Icons] if you add an icon.
• Code must be in the right place (what with the codebase being split in many small files). If there is no right place it probably goes into treemacs-core-utils.el which is where all the general implementation details go.
• New features must be documented in the readme (for example mentioning new config options in the Config Table).
• There must not be any compiler warnings.
• The test suite must pass.

Treemacs uses cask to setup a local testing environment and a Makefile that simplifies compiling and testing the codebase. First run cask install to locally pull treemacs’ dependencies. Then you can use the following Makefile targets:

make prepare

Downloads and updates Cask’s dependencies. Is a dependency of the test and compile targets.

make compile

Compiles the code base (and treats compiler warnings as errors).

make clean

Removes the generated .elc files.

make lint

Runs first compile then clean, even if the former fails.

make test

Runs the testsuite, once in a graphical environment and once in the terminal.

Finally if you want to just add an icon you can take this commit as an example (though the icons have since been moved into their own module in treemacs-icons.el).

If you want to delve into the treemacs’ code base, check out the wiki for some general pointers.

• emacs >= 26.1 (>= 27.1 for tab-bar)
• s
• dash
• cl-lib
• ace-window
• pfuture
• ht
• cfrs
• hydra
• (optionally) evil
• (optionally) projectile
• (optionally) winum
• (optionally) magit
• (optionally) perspective/persp
• (optionally) all-the-icons
• (optionally) python(3)