gdscript-mode.el

;;; gdscript-mode.el --- Provide a major mode for GDScript.
;; URL: https://github.com/akoaysigod/gdscript-mode
;; Version: 20190623-git

(defvar gdscript-mode-map
  (let ((map (make-sparse-keymap)))
    (define-key map [remap newline-and-indent] 'gdscript-newline-and-indent) map))


;;user customization
(defcustom gdscript-tabs-mode indent-tabs-mode
  "Use tabs (t) or spaces (nil)"
  :type 'boolean
  :group 'gdscript)

(defcustom gdscript-tab-width tab-width
  "Indentation width"
  :type 'integer
  :group 'gdscript)



;;Syntax highlighting
(defvar gdscript-builtin-words
  '("null" "bool" "int" "String" "float" "Vector2" "Rect2" "Vector3" "Matrix32" "Plane" "Quat" "AABB" "Matrix3" "Transform"))

(defvar gdscript-keywords
  '("if" "elif" "else" "for" "do"
    "while" "match" "switch" "case"
    "break" "continue" "pass" "return"
    "class" "extends" "is" "self"
    "tool" "signal" "func" "static"
    "const" "enum" "var" "onready"
    "export" "setget" "breakpoint" "preload"
    "yield" "assert" "remote" "master"
    "slave" "sync" "PI" "TAU"
    "INF" "NAN"))

(defun regex-maker (words)
  (regexp-opt words 'symbols))

(defvar gdscript-font-lock
  `((,(regex-maker gdscript-keywords) 1 font-lock-keyword-face)
    (,(regex-maker gdscript-builtin-words) 1 font-lock-type-face)
    (,(rx symbol-start "func" (1+ space) (group (1+ (or word ?_))))
     (1 font-lock-function-name-face))
    (,(rx symbol-start (or "var" "const") (1+ space) (group (1+ (or word ?_))))
     (1 font-lock-variable-name-face))
    ))

(defvar gdscript-syntax-table nil)
(if gdscript-syntax-table
    ()
  (setq gdscript-syntax-table (make-syntax-table))
  (modify-syntax-entry ?\# "\<" gdscript-syntax-table)
  (modify-syntax-entry ?\n ">" gdscript-syntax-table))


;;Indentation
(defun gdscript-should-indent ()
  (save-excursion
    (skip-chars-backward "\r\n\t ");;maybe don't needs this
    (let ((char-eol (char-before (line-end-position))))
      (char-equal ?\: char-eol))))

(defun gdscript-max-indent ()
  (save-excursion
    (skip-chars-backward "\r\n\t ")
    (if (gdscript-should-indent)
        (+ (current-indentation) gdscript-tab-width)
      (current-indentation))))

(defun gdscript-insert-tab (c)
  (if gdscript-tabs-mode
      (insert-char (string-to-char "\t") (floor c gdscript-tab-width))
    (insert-char ?  c)))

(defun gdscript-newline-and-indent ()
  (interactive)
  (delete-horizontal-space t)
  (newline)
  (gdscript-insert-tab (gdscript-max-indent)))

(defun gdscript-indent-back (c)
  (delete-horizontal-space)
  (gdscript-insert-tab (- c gdscript-tab-width)))

(defun is-blank-line? ()
  (= (count-words (line-beginning-position) (line-end-position)) 0))

;;I think I need a custom function to determine current indentation
;;also need to find a better way to do this stuff as if it's a blank line it behaves strange
;;when using save-excursion right now this looks really dumb
(defun gdscript-indent-line ()
  (interactive)
  (let ((ci (current-indentation))
        (co (current-column)))
    (back-to-indentation)
    (cond ((and (<= ci (gdscript-max-indent)) (> ci 0))
           (if (is-blank-line?)
               (gdscript-indent-back ci)
             (progn
               (move-to-column co)
               (save-excursion
                 (back-to-indentation)
                 (gdscript-indent-back ci)))))
          ((= ci 0)
           (if (is-blank-line?)
               (gdscript-insert-tab (gdscript-max-indent))
             (progn
               (move-to-column co)
               (save-excursion
                 (back-to-indentation)
                 (gdscript-insert-tab (gdscript-max-indent))))))
          )
    ))


(define-derived-mode gdscript-mode fundamental-mode "GDScript"
  (setq-local indent-line-function 'gdscript-indent-line)
  (setq-local comment-start "# ")
  (setq-local comment-end "")
  (set-syntax-table gdscript-syntax-table)
  (setq-local font-lock-defaults '(gdscript-font-lock)))

(provide 'gdscript-mode)

(add-to-list 'auto-mode-alist '("\\.gd\\'" . gdscript-mode))

;;; gdscript-mode.el ends here