how to deal with comment in a new lang mode

[Xah]

when writing a new language mode, how can one make comment-dwim work?

i can of course code my own functions dealing with comments, but i
think it is better to use the facilities provided in newcomment.el?

right now i have:

(defun xlsl-comment-dwim (arg)
  (interactive "*P")
  (let ((comment-start-orig comment-start)
        (comment-end-orig comment-end))
    (setq comment-start "// ")
    (setq comment-end "")
    (comment-dwim arg)

    (setq comment-start comment-start-orig)
    (setq comment-end comment-end-orig)
))

and

  (define-key xlsl-mode-map [remap comment-dwim] 'xlsl-comment-dwim)

this works fine when typing the shortcut for comment-dwim on a empty
line to insert comment. But doesnt work as expected when the line is
already a comment. (it does nothing)

any advice apprecated for dealing with comments in a new lang mode.

Thanks.

PS if it matters, i also have my syntax table defined:

(defvar xlsl-mode-syntax-table
  (let ((synTable (make-syntax-table)))
    (modify-syntax-entry ?\/ ". 12b" synTable)
    (modify-syntax-entry ?\n "> b" synTable)

    (modify-syntax-entry ?< "()" synTable)
    (modify-syntax-entry ?> ")(" synTable)
    synTable
    )
  "Syntax table for `xlsl-mode'."
)

The lsl has “// ...” as comment but not “/* ... */”. I dont want it to
be derived mode of c-mode though atm ...

  Xah
∑ http://xahlee.org/

☄