Add Emacs Window Manager (EXWM) Layer AKA SpacemacsOS (#3321)

* Add Emacs Window Manager (EXWM) Layer

The time has come of SpacemacsOS

* set window manager name to EXWM

* update copyright notice

* start server when EXWM is active

When using EXWM, Emacs should be ready to receive clients but the final choice
should be the user's in their shell configuration.

* respect Spacemacs naming conventions and layer organization

* leave keyboard remapping to users

* add EXWM states for Evil

* add support for helm-exwm when helm is in use

* use both exwm-randr and exwm-systemtray

* set up workspaces to match displays by default

* use ido-config instead of the deprecated workaround

When using helm-exwm, its sources distinguish title and class automatically. It
is only necessary to keep the buffer name updated when the window title changes.
When using ido, rename differently for different applications.

* add bindings for common X keys

* use standard prefix commands where available

Spacemacs already has prefix commands for controlling windows.
These are directly available in exwm-state as well as in exwm-insert-state
through leader

* remove most keybindings as they are available directly in exwm-state

* enable exwm directly in the layer configuration

It is safe to enable it here as an existing window manager will simply fail with
a warning.

* add user-configurable variables for RandR and workspaces

By default, create as many workspaces as there are displays and assign them in
RandR order.

* fix naming convention for variables

* use helm for launching applications when possible

* fix conditional helm-exwm leader keys

* remove redundant function

EXWM provides the equivalent

* conform to naming convention for Spacemacs

* separate prefix commands into those for major mode and global

* remove all default bindings

* improve readability

* clean up bindings

* remove obsolete comments

Co-authored-by: M. Domenzain <luis.domenzain@parrot.com>

layers/+window-management/exwm/README.org

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+* EXWM contribution layer for Spacemacs
+
+** Table of Contents                                                  :TOC@4:
+ - [[#exwm-contribution-layer-for-spacemacs][EXWM contribution layer for Spacemacs]]
+   - [[#description][Description]]
+   - [[#install][Install]]
+     - [[#note-about-display-managers][Note about Display Managers]]
+     - [[#not-having-display-managers][Not having Display Managers]]
+     - [[#osx][OSX]]
+   - [[#key-bindings][Key bindings]]
+
+** Description
+The time has arrived when one can finally use Emacs as a Window Manager, long
+ago the concepts of *windows* and *frames* made so much sense when one was
+working in a TTY, and basically that's all the window management you got. In
+these *modern* times though, it sounds silly to have those names. But not
+Anymore!
+
+Thanks to @ch11ng and his [[https://github.com/ch11ng/exwm][EXWM]] project we can now use Emacs as our window
+manager, and all those *windows* that didn't make sense before, now can not only
+hold buffers, but X Windows, that means that you can spawn a Browser Window, or
+your music player, or anything.
+
+I urge you to read the [[https://github.com/ch11ng/exwm/wiki][EXWM Wiki]] for a more in depth explanation and if you can
+contribute, please do so! The purpose of me making this layer is that I find it
+awesome and having nice defaults would make more people dive into it and the
+project would receive more attention and contributions which will only make it
+more awesome, so if you try it and like it, share it!
+
+This is how it looks like:
+
+[[img/spacemacsOS.jpg]]
+
+** Install
+To use this contribution add it to your =~/.spacemacs=
+
+#+begin_src emacs-lisp
+  (setq-default dotspacemacs-configuration-layers '(exwm))
+#+end_src
+
+*** Note about Display Managers
+
+This is most common among Ubuntu and derivative users:
+
+LightDM, GDM, and other Display managers that need a session file will need you
+to copy the [[file:files/exwm.desktop][desktop file]] I bundled with this layer to
+~/usr/local/xsessions/exwm.desktop~, that's what I used on my Ubuntu box, but
+make sure the [[file:files/exwm-start][exwm-start script]] is in your PATH, you can put it in
+~/usr/local/bin/exwm-start~ and that should be enough, next time you log out,
+select the EXWM session instead of the Ubuntu one and you should be alright.
+
+*** Not having Display Managers
+
+If you use Arch, Gentoo, or any other Linux, most probably you'll start your
+configurations via a ~.xinitrc~ file, just append ~exwm-start~ to the end of
+that file and you should be fine. I do recommend to check the [[https://github.com/ch11ng/exwm/wiki][EXWM Wiki]] for more
+details.
+
+*** OSX
+
+If you are an OSX user, please report back on whether this works with xQuartz,
+always back up your data before attempting to try stuff like this.
+
+** Key bindings
+
+As other window managers the ~s~ or *Super* key (Windows Key) is the one that
+is the prefix to every action. We'll use a lot of ~s~.
+
+I have, for convenience, disabled the use of ~C-x~ and ~C-c~ in X windows,
+mainly because that's something we could use for Cutting and Copying text, but if
+you want you can enable it, this layer focuses on less Emacs-y bindings.
+
+| Key Binding           | Description                                    |
+|-----------------------+------------------------------------------------|
+| ~C-q~                 | Send next key pressed to the X window          |
+| ~C-'~                 | Pop shell                                      |
+| ~C-g~                 | Universal GetMeOuttaHere Key from Emacs        |
+| ~C-u~                 | Universal Argument                             |
+| ~C-[0-9]~             | Universal Prefix for [0-9]                     |
+| ~M-m~                 | Spacemacs Leader Key                           |
+| ~s-[1 2 3 ... 8 9 0]~ | Switch to workspace [1 2 3 ... 8 9 10]         |
+| ~s-TAB~               | Switch to last workspace                       |
+| ~s-w~                 | Workspace Switch Menu (kinda like micro-state) |
+| ~s-r~                 | Reset window state                             |
+| ~s-SPC~               | App Launcher                                   |
+| ~s-ESC~               | Lock Screen                                    |
+| ~s-:~ and ~s-;~       | Helm M-x (same as ~SCP :~)                     |
+| ~s-u,U~               | Undo, Redo window configurations               |
+| ~s-b~                 | Show all opened buffers                        |
+| ~s-h,j,k,l~           | Switch to left,lower,upper,right window        |
+| ~s-H,J,K,L~           | Move window to far left,down,lower,upper,right |
+| ~M-s-h,j,k,l~         | Resizing (try them, it's too hard to explain)  |
+| ~s-[,]~               | Switch to prev,next workspace                  |

layers/+window-management/exwm/config.el

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+(defvar exwm-terminal-command "xterm"
+  "Terminal command to run.")
+
+(defvar exwm-locking-command "slock"
+  "Command to run when locking session")
+
+(defvar exwm-hide-tiling-modeline nil
+  "Whether to hide modeline.")
+
+(defvar exwm-leader-key nil
+  "Key to use for EXWM global commands")
+
+(defvar exwm-workspace-switch-wrap t
+  "Whether `exwm/exwm-workspace-next' and `exwm/exwm-workspace-prev' should wrap.")
+
+(defvar exwm-workspace-number nil
+  "Number of workspaces. Defaults to the number of connected displays if `nil'.")
+
+(defvar exwm-randr-command nil
+  "`xrandr' command to set up displays prior to EXWM init.")

layers/+window-management/exwm/files/exwm-start

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+#!/bin/sh
+
+# this makes it work in Ubuntu
+xhost +
+## you might need to append the TTY you are working on
+xinit
+
+wmname EXWM
+
+# Set fallback cursor
+xsetroot -cursor_name left_ptr
+
+# Finally launch emacs and enable exwm
+exec dbus-launch --exit-with-session emacs

layers/+window-management/exwm/files/exwm.desktop

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+[Desktop Entry]
+Name=EXWM
+Comment=Emacs Window Manager
+Exec=exwm-start
+Type=Application

layers/+window-management/exwm/funcs.el

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+(defun exwm/exwm-bind-command (key command &rest bindings)
+  "Bind KEYs to COMMANDs globally"
+  (while key
+    (exwm-input-set-key (kbd key)
+                        `(lambda ()
+                           (interactive)
+                           (start-process-shell-command ,command nil
+                                                        ,command)))
+    (setq key (pop bindings)
+          command
+          (pop bindings))))
+
+(defun exwm/exwm-workspace-next ()
+  "Switch to next exwm-workspace (to the right)."
+  (interactive)
+  (let* ((only-workspace? (equal exwm-workspace-number 1))
+         (overflow? (= exwm-workspace-current-index (1- exwm-workspace-number))))
+    (cond
+     (only-workspace? nil)
+     (overflow? (when exwm-workspace-switch-wrap
+                  (exwm-workspace-switch 0)))
+     (t (exwm-workspace-switch (1+ exwm-workspace-current-index))))))
+
+(defun exwm/exwm-workspace-prev ()
+  "Switch to next exwm-workspace (to the left)."
+  (interactive)
+  (let* ((only-workspace? (equal exwm-workspace-number 1))
+         (overflow? (= exwm-workspace-current-index 0)))
+    (cond
+     (only-workspace? nil)
+     (overflow? (when exwm-workspace-switch-wrap
+                  (exwm-workspace-switch (1- exwm-workspace-number))))
+     (t (exwm-workspace-switch (1- exwm-workspace-current-index))))))
+
+;; Quick swtiching between workspaces
+(defvar exwm--toggle-workspace 0 "Previously selected workspace. Used with `exwm/jump-to-last-exwm'.")
+
+(defun exwm/jump-to-last-exwm ()
+  (interactive)
+  (exwm-workspace-switch exwm--toggle-workspace))
+
+(defadvice exwm-workspace-switch
+    (before save-toggle-workspace activate)
+  (setq exwm--toggle-workspace exwm-workspace-current-index))
+
+(defun exwm/exwm-app-launcher ()
+  "Launches an application in your PATH.
+Can show completions at point for COMMAND using helm"
+  (interactive)
+  (call-interactively
+   (if (configuration-layer/package-usedp 'helm)
+       'helm-run-external-command
+     'async-shell-command)))
+
+(defun exwm/exwm-lock ()
+  (interactive)
+  (start-process "" nil exwm-locking-command))
+
+;; Other utilities
+(defun exwm//flatenum (i ls)
+  (if ls (cons i (cons (first ls) (exwm//flatenum  (1+ i) (cdr ls)))) (list)))

layers/+window-management/exwm/packages.el

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+;;; packages.el --- exwm Layer packages File for Spacemacs
+;;
+;; Copyright (c) 2012-2014 Sylvain Benner
+;; Copyright (c) 2014-2018 Sylvain Benner & Contributors
+;;
+;; Author: Sylvain Benner <sylvain.benner@gmail.com>
+;; URL: https://github.com/syl20bnr/spacemacs
+;;
+;; This file is not part of GNU Emacs.
+;;
+;;; License: GPLv3
+
+;; List of all packages to install and/or initialize. Built-in packages
+;; which require an initialization must be listed explicitly in the list.
+(defconst exwm-packages
+    '(cl-generic
+      (helm-exwm :requires helm)
+      (evil-exwm-state :location (recipe :fetcher github
+                                         :repo "domenzain/evil-exwm-state"))
+      (xelb :location (recipe :fetcher github
+                              :repo "ch11ng/xelb")
+            :step pre)
+      (exwm :location (recipe :fetcher github
+                              :repo "ch11ng/exwm")
+            :step pre)))
+
+(defun exwm/init-helm-exwm ()
+  ;; when helm is used activate extra EXWM features
+  (use-package helm-exwm
+    :config
+    (progn
+      ;; Add EXWM buffers to a specific section in helm mini
+      (setq exwm-helm-exwm-emacs-buffers-source
+            (helm-exwm-build-emacs-buffers-source))
+      (setq exwm-helm-exwm-source (helm-exwm-build-source))
+      (setq helm-mini-default-sources `(exwm-helm-exwm-emacs-buffers-source
+                                        exwm-helm-exwm-source
+                                        helm-source-recentf
+                                        helm-source-buffer-not-found))
+      ;; Add a prefix command to choose among EXWM buffers only
+      (spacemacs/set-leader-keys "WW" 'helm-exwm))))
+
+(defun exwm/init-evil-exwm-state ()
+  (use-package evil-exwm-state
+    :init
+    (spacemacs/define-evil-state-face "exwm" "firebrick1")
+    (spacemacs/define-evil-state-face "exwm-insert" "chartreuse3")))
+
+(defun exwm/init-cl-generic ()
+  (use-package cl-generic
+    :demand))
+
+(defun exwm/init-xelb ()
+  (use-package xelb))
+
+(defun exwm/init-exwm ()
+  (use-package exwm-randr)
+  (use-package exwm-systemtray)
+  (use-package exwm-config)
+  (use-package exwm
+    :init
+    ;; Disable dialog boxes since they are unusable in EXWM
+    (setq use-dialog-box nil)
+    ;; Use as many workspaces as there are connected displays
+    ;; TODO: Is there a way of doing this with xelb?
+    (defvar exwm--randr-displays (split-string
+                            (shell-command-to-string
+                             "xrandr | grep ' connected' | cut -d' ' -f1 "))
+      "The list of connected RandR displays")
+    ;; Set at least as many workspaces as there are connected displays.
+    ;; At the user's option, begin with even more workspaces
+    (setq exwm-workspace-number
+          (if exwm-workspace-number
+              (max exwm-workspace-number (list-length exwm--randr-displays))
+              (list-length exwm--randr-displays)))
+    ;; The first workspaces will match the order in RandR
+    (setq exwm-randr-workspace-output-plist
+          (exwm//flatenum 0 exwm--randr-displays))
+
+    ;; You may want Emacs to show you the time
+    (display-time-mode t)
+    (when exwm-hide-tiling-modeline
+      (add-hook 'exwm-mode-hook #'hidden-mode-line-mode))
+
+    :config
+    (add-hook 'exwm-update-title-hook
+              (lambda ()
+                (exwm-workspace-rename-buffer exwm-title)))
+
+    (when 'dotspacemacs-use-ido
+      (exwm-config-ido)
+      ;; Only rename windows intelligently when using ido.
+      ;; When using helm-exwm, the source distinguishes title and class.
+      (add-hook 'exwm-update-class-hook
+                (lambda ()
+                  (unless (or (string-prefix-p "sun-awt-X11-" exwm-instance-name)
+                              (string= "gimp" exwm-instance-name))
+                    (exwm-workspace-rename-buffer exwm-class-name))))
+      (add-hook 'exwm-update-title-hook
+                (lambda ()
+                  (when (or (not exwm-instance-name)
+                            (string-prefix-p "sun-awt-X11-" exwm-instance-name)
+                            (string= "gimp" exwm-instance-name))
+                    (exwm-workspace-rename-buffer exwm-title)))))
+
+    ;; Remove ALL bindings
+    (define-key exwm-mode-map "\C-c\C-f" nil)
+    (define-key exwm-mode-map "\C-c\C-h" nil)
+    (define-key exwm-mode-map "\C-c\C-k" nil)
+    (define-key exwm-mode-map "\C-c\C-m" nil)
+    (define-key exwm-mode-map "\C-c\C-q" nil)
+    (define-key exwm-mode-map "\C-c\C-t\C-f" nil)
+    (define-key exwm-mode-map "\C-c\C-t\C-m" nil)
+    ;; Let easy-menu figure out the keys
+    (easy-menu-add-item exwm-mode-menu '()
+                        ["Toggle mode-line" exwm-layout-toggle-mode-line])
+    (easy-menu-add-item exwm-mode-menu '()
+                        ["Move X window to" exwm-workspace-move-window])
+
+    (exwm/exwm-bind-command
+     "s-'"  exwm-terminal-command
+     "<s-return>"  exwm-terminal-command
+     "<XF86MonBrightnessUp>"   "light -A 5"
+     "<XF86MonBrightnessDown>" "light -U 5"
+     "<XF86AudioLowerVolume>" "amixer -D pulse -- sset Master unmute 3%-"
+     "<XF86AudioRaiseVolume>" "amixer -D pulse -- sset Master unmute 3%+"
+     "<XF86AudioMute>"        "amixer -D pulse -- sset Master toggle"
+     "<XF86AudioMicMute>"     "amixer -D pulse -- sset Capture toggle")
+
+    ;; Pass all keypresses to emacs in line mode.
+    (setq exwm-input-line-mode-passthrough t)
+
+
+    ;; `exwm-input-set-key' allows you to set a global key binding (available in
+    ;; any case). Following are a few examples.
+
+    (exwm-input-set-key (kbd "s-i") 'exwm-input-toggle-keyboard)
+    (exwm-input-set-key (kbd "M-m") 'spacemacs-cmds)
+    (exwm-input-set-key (kbd "C-q") 'exwm-input-send-next-key)
+    ;; + We always need a way to go back to line-mode from char-mode
+    (exwm-input-set-key (kbd "s-r") 'exwm-reset)
+
+    (exwm-input-set-key (kbd "s-f") #'exwm/exwm-layout-toggle-fullscreen)
+    (exwm-input-set-key (kbd "<s-tab>") #'exwm/jump-to-last-exwm)
+    ;; + Bind a key to switch workspace interactively
+    (exwm-input-set-key (kbd "s-w") 'exwm-workspace-switch)
+    (exwm-input-set-key (kbd "s-SPC") #'exwm/exwm-app-launcher)
+    (exwm-input-set-key (kbd "s-l") 'exwm/exwm-lock)
+
+    ;; set up evil escape
+    (exwm-input-set-key [escape] 'evil-escape)
+
+    ;; Bindings available everywhere
+    (spacemacs/declare-prefix "W" "EXWM")
+    (spacemacs/set-leader-keys
+      "Wp" 'exwm/exwm-workspace-prev
+      "Wn" 'exwm/exwm-workspace-next
+      "WA" 'exwm-workspace-add
+      "Wd" 'exwm-workspace-delete
+      "Wr" 'exwm-restart
+      "Wl" 'exwm/exwm-lock
+      "Wa" 'exwm/exwm-app-launcher)
+
+    ;; Bindings for use only on EXWM buffers
+    (spacemacs/declare-prefix-for-mode 'exwm-mode
+      "mT" "toggle")
+    (spacemacs/set-leader-keys-for-major-mode 'exwm-mode
+      "r" 'exwm-reset
+      "Tf" 'exwm-layout-toggle-fullscreen
+      "Tt" 'exwm-floating-toggle-floating
+      "Tm" 'exwm-layout-toggle-mode-line)
+
+    (exwm-randr-enable)
+    (exwm-systemtray-enable)
+
+    (if exwm-randr-command
+     (start-process-shell-command
+      "xrandr" nil exwm-randr-command))
+
+    (exwm-init)
+    (server-start)
+    ))