From 287595960984882e03e0b31aa882eb14cf76e034 Mon Sep 17 00:00:00 2001
From: David Robillard <d@drobilla.net>
Date: Fri, 25 Dec 2020 15:28:53 +0100
Subject: Add automatic indentation based on clang-format configuration

---
 emacs/.emacs.d/init.el | 53 +++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 52 insertions(+), 1 deletion(-)

(limited to 'emacs/.emacs.d')

diff --git a/emacs/.emacs.d/init.el b/emacs/.emacs.d/init.el
index c4da671..be3946b 100644
--- a/emacs/.emacs.d/init.el
+++ b/emacs/.emacs.d/init.el
@@ -25,6 +25,51 @@
 
 (add-hook 'dired-mode-hook (lambda () (dired-hide-details-mode)))
 
+;;; Code formatting
+
+(defun get-clang-format-option (config-str field is-num)
+  "Retrieve a config option from a clang-format config."
+  (cond (is-num
+         (let ((primary-match (s-match (concat "^" field ":[ \t]*[0-9]+") config-str)))
+           (if primary-match
+               (string-to-number (car (s-match "[0-9]+" (car primary-match))))
+             0)))
+        (t
+         (let ((primary-match (s-match (concat "^" field ":[ \t]*[A-Za-z]+") config-str)))
+           (if primary-match
+               (car (s-match "[A-Za-z]+$" (car primary-match)))
+             "")))))
+
+(defun clang-format-c-mode-hook ()
+  (let* ((clang-format-config
+          (shell-command-to-string "clang-format -dump-config"))
+         (c-offset (get-clang-format-option clang-format-config "IndentWidth" t))
+         (tabs-str (get-clang-format-option clang-format-config "UseTab" nil))
+         (base-style
+          (get-clang-format-option clang-format-config "BasedOnStyle" nil)))
+    (progn
+      (if (> c-offset 0)
+          (setq-local c-basic-offset c-offset)
+        (if (not (equal "" base-style))
+            (cond ((or (equal "LLVM" base-style)
+                       (equal "Google" base-style)
+                       (equal "Chromium" base-style)
+                       (equal "Mozilla" base-style))
+                   (setq-local c-basic-offset 2))
+                  ((equal "WebKit" base-style)
+                   (setq-local c-basic-offset 4)))))
+      (if (not (equal "" tabs-str))
+          (if (not (string-equal "Never" tabs-str))
+              (setq-local indent-tabs-mode t)
+            (setq-local indent-tabs-mode nil))
+        (if (not (equal "" base-style))
+            (cond ((or (equal "LLVM" base-style)
+                       (equal "Google" base-style)
+                       (equal "Chromium" base-style)
+                       (equal "Mozilla" base-style)
+                       (equal "WebKit" base-style))
+                   (setq-local indent-tabs-mode nil))))))))
+
 ;;; Packages
 
 (require 'package)
@@ -36,7 +81,12 @@
     (package-install 'use-package)))
 
 (setq use-package-always-ensure t)
-(use-package clang-format :commands (c-mode c++-mode))
+
+(use-package clang-format
+  :commands (c-mode c++-mode objc-mode)
+  :after (s)
+  :hook (c-mode-common . clang-format-c-mode-hook))
+
 (use-package counsel :after (ivy) :config (counsel-mode))
 (use-package counsel-gtags :commands ggtags-mode)
 (use-package counsel-projectile :after (counsel projectile))
@@ -494,6 +544,7 @@
 (add-to-list 'auto-mode-alist '("\\.jsonld" . json-mode))
 (add-to-list 'auto-mode-alist '("\\.tesc"   . glsl-mode))
 (add-to-list 'auto-mode-alist '("\\.tese"   . glsl-mode))
+(add-to-list 'auto-mode-alist '("\\.clang-format" . yaml-mode))
 
 ;;; Projectile
 
-- 
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