C: Fix cc-format-with-uncrustify

.emacs.d/lisp/init-cc.el

@@ -82,6 +82,7 @@ If the command is not `make', run it normally. "
         (compile (format "%s -B" compile-command))
       (recompile))))
 
+;; TODO: See https://github.com/koko1000ban/emacs-uncrustify-mode.
 (defun ambrevar/cc-format-with-uncrustify (&optional cfg-file start end)
   "Run uncrustify(1) on current buffer or region."
   (interactive "f\nr")
@@ -90,19 +91,38 @@ If the command is not `make', run it normally. "
                    (point-min)))
         (end (or (and (region-active-p) end)
                  (point-max)))
-        (formatbuf (get-buffer-create " *C format buffer*")))
+        (formatbuf (get-buffer-create " *C format buffer*"))
+        (stderr (make-temp-file "uncrustify")))
     (setq status
-          (call-process-region start end "uncrustify" nil formatbuf nil "-lc" "-q" "-c"
+          (call-process-region start end
+                               "uncrustify"
+                               nil (list formatbuf stderr) nil
+                               ;; "-lc" ; Uncrustify should be able to auto-detect.
+                               "-c"
                                (or cfg-file
                                    (expand-file-name ".uncrustify.cfg" (getenv "HOME")))))
     (if (/= status 0)
-        (error "error running uncrustify")
-      (let ((old-point (point)))
+        (let ((error-message
+               (with-temp-buffer
+                 (insert-file-contents-literally stderr)
+                 (buffer-string))))
+          (delete-file stderr)
+          (kill-buffer formatbuf)
+          (error "error running uncrustify: %s" error-message))
+      (delete-file stderr)
+      (let ((old-line (line-number-at-pos))
+            (old-column (current-column))
+            (old-window-start-line (- (line-number-at-pos)
+                                      (line-number-at-pos (window-start)))))
         (save-mark-and-excursion
           (delete-region (or start (point-min)) (or end (point-max)))
           (insert-buffer-substring formatbuf))
-        (goto-char old-point))
-      (kill-buffer formatbuf))))
+        (goto-line old-line)
+        (move-to-column old-column)
+        (recenter old-window-start-line))
+      (kill-buffer formatbuf)))
+  ;; Return nil if in a `write-file-functions'.
+  nil)
 
 (defun ambrevar/cc-format-file-lookup ()
   "Find .clang-format or .uncrustify.cfg in parent folder up to Git root.
@@ -138,7 +158,7 @@ This is suitable for a `before-save-hook'."
 (defun ambrevar/cc-turn-on-format ()
   "Add `ambrevar/cc-format' to `before-save-hook' locally.
 You can add your mode hook (e.g. `c-mode-hook')."
-  (add-hook 'before-save-hook 'ambrevar/cc-format nil 'local))
+  (add-hook 'write-file-functions 'ambrevar/cc-format nil 'local))
 
 ;;; GMP documentation
 (with-eval-after-load "info-look"
@@ -306,8 +326,8 @@ fprintf(stderr, \"\\n\"); \\
 #include <unistd.h>
 
 int main(int argc, char **argv) {" \n
-> @ _ \n
-> "return 0;
+  > @ _ \n
+  > "return 0;
 }" \n)
 
 (define-skeleton cc-usage-version