Question

I’d like to mix org-mode and c-mode in Emacs. Everything inside a
comment should be org-mode, the rests should be default major-mode
c-mode:

/*
Org-mode here
** Section 1
  text
** Section 2
  text
Org-mode should end here
*/

func1()
{
}

I tried using nXhtml multi-major-mode, I guess there are other modes
that support multimodes too. My problem now is that if I type TAB
on “section 2” then all below “Section 2” will be folded and
made invisible. But I would like to contain the region that org-mode
folds/unfolds to the comment section. The TAB should only fold/unfold
till the “*/”.

I wonder how I can achieve this?

Answer 1

I found a solution:
http://lists.gnu.org/archive/html/emacs-orgmode/2011-01/msg00036.html
lists a patch for org-mode:

--- emacs-23.2/lisp/org/org.el  2010-04-04 00:26:08.000000000 +0200
+++ src/c51/mk/org.el   2011-01-02 20:26:10.266860827 +0100
@@ -5245,6 +5245,8 @@
 (defun org-cycle-internal-local ()
   "Do the local cycling action."
   (org-back-to-heading)
+  (cond 
+   ((not (looking-at (concat outline-regexp "\s*#" )))
   (let ((goal-column 0) eoh eol eos level has-children children-skipped)
     ;; First, some boundaries
     (save-excursion
@@ -5318,7 +5320,7 @@
       (hide-subtree)
       (message "FOLDED")
       (setq org-cycle-subtree-status 'folded)
-      (run-hook-with-args 'org-cycle-hook 'folded)))))
+      (run-hook-with-args 'org-cycle-hook 'folded)))))))

 ;;;###autoload
 (defun org-global-cycle (&optional arg)
--- emacs-23.2/lisp/outline.el  2010-04-04 00:26:04.000000000 +0200
+++ src/c51/mk/outline.el   2011-01-02 20:35:17.303609833 +0100
@@ -913,8 +913,15 @@
       ;; Then unhide the top level headers.
       (outline-map-region
        (lambda ()
-    (if (<= (funcall outline-level) levels)
-        (outline-show-heading)))
+    (if (<= (funcall outline-level) level)
+          (if (looking-at (concat outline-regexp "\s*#" ))
+          (progn
+            (outline-show-heading )
+            (show-entry ))
+        (outline-show-heading))))
+;;       (lambda ()
+;;  (if (<= (funcall outline-level) levels)
+;;      (outline-show-heading)))
        beg end)))
   (run-hooks 'outline-view-change-hook))

@@ -994,7 +1001,11 @@
       (outline-map-region
        (lambda ()
     (if (<= (funcall outline-level) level)
-        (outline-show-heading)))
+          (if (looking-at (concat outline-regexp "\s*#" ))
+          (progn
+            (outline-show-heading )
+            (show-entry ))
+          (outline-show-heading))))
        (point)
        (progn (outline-end-of-subtree)
          (if (eobp) (point-max) (1+ (point)))))))

This patch has to be applied by hand, its not that difficult.
It adds the marker *# that will break the indention. @bzg pointed out
the M-x orgstruct-mode RET mode, credits to him. Now I can write in c.mode with orgstruct-mode in the background (no multi-major-mode needed any more):

/*
Org-mode here
** Section 1
  text
** Section 2
  text
*#
Org-mode should end here
*/

And I will have org-mode in comments, The Section 1 and Section 2 will fold until the *# marker.