Add some extra bibtex stuff

init.el

@@ -136,7 +136,8 @@
                 tab-width 4
                 fill-column 80
                 comment-multi-line t
-                comment-empty-lines 'eol)
+                comment-empty-lines 'eol
+                show-trailing-whitespace t)
 
   ;; Tree sitter download locations
   (setq treesit-language-source-alist
@@ -917,6 +918,81 @@ COMMAND and COMINT are like `compile'."
                `(,(concat
                    (regexp-opt '("gschema" "gresource" "ui")) "\\'") . nxml-mode)))
 
+;; Bibtex (built in)
+(use-package bibtex
+  :ensure nil
+  :defer nil
+  :config
+  (defun my/bibtex-in-entry-p (&optional exclude-braces)
+    "Return t is point is inside a BibTeX entry.
+When EXCLUDE-BRACES is non-nil, don't count the first and last brace of the
+entry as in the entry. That is, if the point is on the first { or last } of the
+entry, return nil."
+    (save-excursion
+      ;; go to top level and check if the character at point is {
+      (when (and (not exclude-braces) (= ?{ (char-after)))
+        (forward-char))
+      (let ((start-pos (point))
+            (last-valid (point)))
+        (condition-case _
+            (while t
+              (up-list 1 t t)
+              (setq last-valid (point)))
+          (error
+           (and
+            (= ?\} (char-before last-valid))
+            ;; up-point moves to the char after the last brace, so if the point
+            ;; started there, we aren't in the entry
+            (not (= start-pos last-valid))
+            (or (not exclude-braces)
+                (not (= start-pos (1- last-valid))))))))))
+  (defvar my/bibtex-indent-width 4
+    "Width to indent for `my/bibtex-calculate-indentation'.")
+  (defun my/bibtex-calculate-indentation ()
+    "Calculate the column to indent to on the current line."
+    (save-excursion
+      (back-to-indentation)
+      (if (my/bibtex-in-entry-p t)
+          my/bibtex-indent-width
+        0)))
+  (defun my/bibtex-empty-line-p ()
+    "Return t if the current line is only blank characters."
+    (save-excursion
+      (beginning-of-line)
+      (looking-at (rx (* blank) eol))))
+  (defun my/bibtex-indent-line ()
+    "Indent the current line."
+    (interactive)
+    (save-excursion
+      (beginning-of-line)
+      (when (my/bibtex-empty-line-p)
+        (delete-region (point) (match-end 0)))
+      (indent-to (my/bibtex-calculate-indentation)))
+    (when (looking-at (rx (+ blank) eol))
+      (end-of-line)))
+  (defun my/bibtex-indent-or-find-text ()
+    "Either indent the current line or jump to the current fields text.
+If the current line is only whitespace call `my/bibtex-calculate-indentation',
+otherwise, call `bibtex-find-text'."
+    (interactive)
+    (if (my/bibtex-empty-line-p)
+        (my/bibtex-indent-line)
+      (bibtex-find-text)))
+  (defun my/bibtex-indent-or-find-text-and-insert ()
+    "Like `my/bibtex-indent-or-find-text', but enter insert mode after."
+    (interactive)
+    (my/bibtex-indent-or-find-text)
+    (if (my/bibtex-empty-line-p)
+        (evil-append 1)
+      (evil-insert 1)))
+  (defun my/-bibtex-setup-indent ()
+    (setq-local indent-line-function 'my/bibtex-indent-line))
+  (add-hook 'bibtex-mode-hook 'my/-bibtex-setup-indent)
+  (define-key bibtex-mode-map (kbd "RET") 'newline-and-indent)
+  (define-key bibtex-mode-map (kbd "TAB") 'my/bibtex-indent-or-find-text)
+  (evil-define-key 'normal bibtex-mode-map
+    (kbd "TAB") 'my/bibtex-indent-or-find-text-and-insert))
+
 ;; AUCTeX
 (use-package auctex
   :hook ((LaTeX-mode . turn-on-reftex)