Add highlight-indentation

Cask

@@ -27,6 +27,7 @@
 
 ;; UI --- core/core-ui.el
 (depends-on "visual-fill-column")
+(depends-on "highlight-indentation" :git "https://github.com/localredhead/Highlight-Indentation-for-Emacs")
 (depends-on "rainbow-delimiters")
 (depends-on "rainbow-mode")
 (depends-on "nlinum")

core/core-ui.el

@@ -145,6 +145,24 @@
 
 (use-package visual-fill-column :defer t)
 
+(use-package highlight-indentation
+  :commands (highlight-indentation-mode highlight-indentation-current-column-mode)
+  :init
+  (add-hook! (web-mode nxml-mode yaml-mode json-mode scss-mode
+              c-mode-common ruby-mode python-mode lua-mode)
+    'highlight-indentation-mode)
+
+  :config
+  ;; A long-winded method for ensuring whitespace is maintained (so that
+  ;; highlight-indentation-mode can display them consistently)
+  (add-hook! highlight-indentation-mode
+    (if highlight-indentation-mode
+        (progn
+          (narf/add-whitespace)
+          (add-hook 'after-save-hook 'narf/add-whitespace nil t))
+     (remove-hook 'after-save-hook 'narf/add-whitespace t)))
+  (add-hook 'before-save-hook 'delete-trailing-whitespace))
+
 (use-package rainbow-delimiters
   :commands rainbow-delimiters-mode
   :init

core/defuns/defuns-ui.el

@@ -46,5 +46,35 @@
       (compose-region beg end how 'decompose-region))
     nil))
 
+;;;###autoload
+(defun narf/add-whitespace (&optional start end)
+  (interactive (progn (barf-if-buffer-read-only)
+                      (if (use-region-p)
+                          (list (region-beginning) (region-end))
+                        (list nil nil))))
+  (save-match-data
+    (save-excursion
+      (let ((end-marker (copy-marker (or end (point-max))))
+            (start (or start (point-min))))
+        (goto-char start)
+        (while (and (re-search-forward "^$" end-marker t) (not (>= (point) end-marker)))
+          (let (line-start line-end)
+            (save-excursion
+              (forward-line -1)
+              (setq line-start (point)
+                    line-end   (save-excursion (back-to-indentation) (point)))
+              (if (and (= line-start line-end)
+                       (/= line-end (line-end-position)))
+                  (progn
+                    (forward-line 2)
+                    (setq line-start (point)
+                          line-end   (save-excursion (back-to-indentation) (point)))
+                    (forward-line -1))
+                (forward-line 1))
+              (insert (make-string (- line-end line-start) 32))))
+          (forward-line 1)))))
+  (set-buffer-modified-p nil)
+  nil)
+
 (provide 'defuns-ui)
 ;;; defuns-ui.el ends here