[Patch] hard-widen-limits [was Re: Syntax tables for multiple modes [was: bug#22983: syntax-ppss returns wrong result.]]

[Vitalie Spinu]

>> On Mon, Mar 21 2016 02:05, Vitalie Spinu wrote:

>> Are you interested in working on a patch? Also Cc'ing Stefan.

> My knowledge of emacs C internals is close to 0. Elisp side (and probably C
> side) of this is trivial. I will look into it but I don't think I am the best
> person for that.

The widen part turned to be easy.  Will look at parse-partial-sexp tomorrow.

 Vitalie

>From eafcff9e72499e3bb6dc462d406dd33a885e3d49 Mon Sep 17 00:00:00 2001
From: Vitalie Spinu <address@hidden>
Date: Mon, 21 Mar 2016 05:41:55 +0100
Subject: [PATCH] Implement hard-narrowing

 `widen` now respects restrictions imposed by new variable `hard-widen-limits`
---
 src/buffer.c  |  5 +++++
 src/editfns.c | 14 +++++++++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/buffer.c b/src/buffer.c
index f06d7e0..5232c49 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -6219,6 +6219,11 @@ and disregard a `read-only' text property if the 
property value
 is a member of the list.  */);
   Vinhibit_read_only = Qnil;
 
+  DEFVAR_LISP ("hard-widen-limits", Vhard_widen_limits,
+              doc: /* When non-nil `widen` will widen to these limits.
+Must be a cons of the form (MIN . MAX) where MIN and MAX are integers or 
markers.  */);
+  Vhard_widen_limits = Qnil;
+
   DEFVAR_PER_BUFFER ("cursor-type", &BVAR (current_buffer, cursor_type), Qnil,
                     doc: /* Cursor to use when this buffer is in the selected 
window.
 Values are interpreted as follows:
diff --git a/src/editfns.c b/src/editfns.c
index 2ac0537..fb1f652 100644
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -3480,12 +3480,24 @@ DEFUN ("delete-and-extract-region", 
Fdelete_and_extract_region,
     return empty_unibyte_string;
   return del_range_1 (XINT (start), XINT (end), 1, 1);
 }
+
 
 DEFUN ("widen", Fwiden, Swiden, 0, 0, "",
        doc: /* Remove restrictions (narrowing) from current buffer.
-This allows the buffer's full text to be seen and edited.  */)
+This allows the buffer's full text to be seen and edited.
+If `hard-widen-limits` is non-nil, widen only to those limits.  */)
   (void)
 {
+
+  if (! NILP (Vhard_widen_limits))
+    {
+      CHECK_CONS(Vhard_widen_limits);
+      Lisp_Object hbeg = XCAR(Vhard_widen_limits);
+      Lisp_Object hend = XCDR(Vhard_widen_limits);
+      Fnarrow_to_region(hbeg, hend);
+      return Qnil;
+    }
+
   if (BEG != BEGV || Z != ZV)
     current_buffer->clip_changed = 1;
   BEGV = BEG;
-- 
2.5.0