Add :ui zen module

This, combined with the new ':tools (lookup +dictionary)' feature will
eventually replace the ':app write' module.

docs/index.org

@@ -275,3 +275,4 @@ Aesthetic modules that affect the Emacs interface or user experience.
 + vi-tilde-fringe - TODO
 + [[file:../modules/ui/window-select/README.org][window-select]] =+switch-window +numbers= - TODO
 + [[file:../modules/ui/workspaces/README.org][workspaces]] - Isolated workspaces
++ [[file:../modules/ui/zen/README.org][zen]] - Distraction-free coding (or writing)

init.example.el

@@ -42,6 +42,7 @@
        vi-tilde-fringe   ; fringe tildes to mark beyond EOB
        window-select     ; visually switch windows
        workspaces        ; tab emulation, persistence & separate workspaces
+       ;;zen               ; distraction-free coding or writing
 
        :editor
        (evil +everywhere); come to the dark side, we have cookies

modules/ui/zen/config.el

@@ -0,0 +1,42 @@
+;;; ui/zen/config.el -*- lexical-binding: t; -*-
+
+(defvar +zen-mixed-pitch-modes '(markdown-mode org-mode)
+  "What major-modes to enable `mixed-pitch-mode' in with `writeroom-mode'.")
+
+
+;;
+;;; Packages
+
+(after! writeroom-mode
+  (setq writeroom-fullscreen-effect nil
+        writeroom-maximize-window nil)
+
+  ;; Adjust margins when text size is changed
+  (advice-add #'text-scale-adjust :after #'visual-fill-column-adjust))
+
+
+(use-package! mixed-pitch
+  :hook (writeroom-mode . +zen-enable-mixed-pitch-mode-h)
+  :config
+  (defun +zen-enable-mixed-pitch-mode-h ()
+    "Enable `mixed-pitch-mode' when in `+zen-mixed-pitch-modes'."
+    (when (apply #'derived-mode-p +zen-mixed-pitch-modes)
+      (mixed-pitch-mode (if writeroom-mode +1 -1))))
+
+  (pushnew! mixed-pitch-fixed-pitch-faces
+            'org-date
+            'org-special-keyword
+            'org-property-value
+            'org-ref-cite-face
+            'org-tag
+            'org-todo-keyword-todo
+            'org-todo-keyword-habt
+            'org-todo-keyword-done
+            'org-todo-keyword-wait
+            'org-todo-keyword-kill
+            'org-todo-keyword-outd
+            'org-todo
+            'org-indent
+            'font-lock-comment-face
+            'line-number
+            'line-number-current-line))

modules/ui/zen/packages.el

@@ -0,0 +1,5 @@
+;; -*- no-byte-compile: t; -*-
+;;; ui/zen/packages.el
+
+(package! writeroom-mode)
+(package! mixed-pitch)