Subject: bug#36190: 27.0.50; `put-text-property' etc. with buffer argument calls current buffer's `after-change-functions'

From: Pip Cet <[email-masked]>
Date: Sat, 6 Jul 2019 15:27:41 +0000

On Sat, Jul 6, 2019 at 8:08 AM Eli Zaretskii <[email-masked]> wrote:
> > Sounds good to me. The attached patch contains the comments and a hint
> > in the documentation. (Maybe the comments should be a FIXME, because
> > there's really no need to switch buffers at all when there are no
> > applicable hooks?)
>
> I'm okay with adding such a FIXME.

Added.

>
> > Obviously, feel free to reword as you consider appropriate.
>
> LGTM, with a couple of minor comments below.  Feel free to push after
> fixing those.

I don't have push access, so I hope it's okay just to send the new patch.

Thanks for the review!
From 7e3b17ce5704b5327b977673382688f8e7f5b4c9 Mon Sep 17 00:00:00 2001
From: Pip Cet <[email-masked]>
Date: Sat, 6 Jul 2019 15:21:04 +0000
Subject: [PATCH] Update current buffer when changing text properties.

* src/textprop.c (add_text_properties_1, set_text_properties)
(set_text_properties_1, Fremove_text_properties): Switch buffer if
necessary.

* doc/lispref/text.texi (Examining Properties): Document performance
FIXME.
---
 doc/lispref/text.texi |  2 +-
 src/textprop.c        | 66 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 67 insertions(+), 1 deletion(-)

diff --git a/doc/lispref/text.texi b/doc/lispref/text.texi
index c4fc5247a1..ca0dd6642d 100644
--- a/doc/lispref/text.texi
+++ b/doc/lispref/text.texi
@@ -2800,7 +2800,7 @@ Examining Properties
 
   These functions handle both strings and buffers.  Keep in mind that
 positions in a string start from 0, whereas positions in a buffer start
-from 1.
+from 1.  Passing a buffer other than the current buffer may be slow.
 
 @defun get-text-property pos prop &optional object
 This function returns the value of the @var{prop} property of the
diff --git a/src/textprop.c b/src/textprop.c
index 9023f4efa0..44c333256a 100644
--- a/src/textprop.c
+++ b/src/textprop.c
@@ -1142,6 +1142,18 @@ DEFUN ("previous-single-property-change", Fprevious_single_property_change,
 add_text_properties_1 (Lisp_Object start, Lisp_Object end,
 		       Lisp_Object properties, Lisp_Object object,
 		       enum property_set_type set_type) {
+  /* Ensure we run the modification hooks for the right buffer,
+     without switching buffers twice (bug 36190).  FIXME: Switching
+     buffers is slow and often unnecessary.  */
+  if (BUFFERP (object) && XBUFFER (object) != current_buffer)
+    {
+      ptrdiff_t count = SPECPDL_INDEX ();
+      record_unwind_current_buffer ();
+      set_buffer_internal (XBUFFER (object));
+      return unbind_to (count, add_text_properties_1 (start, end, properties,
+						      object, set_type));
+    }
+
   INTERVAL i, unchanged;
   ptrdiff_t s, len;
   bool modified = false;
@@ -1343,6 +1355,19 @@ face(s) are retained.  This is done by setting the `face' property to
 set_text_properties (Lisp_Object start, Lisp_Object end, Lisp_Object properties,
 		     Lisp_Object object, Lisp_Object coherent_change_p)
 {
+  /* Ensure we run the modification hooks for the right buffer,
+     without switching buffers twice (bug 36190).  FIXME: Switching
+     buffers is slow and often unnecessary.  */
+  if (BUFFERP (object) && XBUFFER (object) != current_buffer)
+    {
+      ptrdiff_t count = SPECPDL_INDEX ();
+      record_unwind_current_buffer ();
+      set_buffer_internal (XBUFFER (object));
+      return unbind_to (count,
+			set_text_properties (start, end, properties,
+					     object, coherent_change_p));
+    }
+
   INTERVAL i;
   bool first_time = true;
 
@@ -1413,6 +1438,20 @@ set_text_properties (Lisp_Object start, Lisp_Object end, Lisp_Object properties,
 set_text_properties_1 (Lisp_Object start, Lisp_Object end,
 		       Lisp_Object properties, Lisp_Object object, INTERVAL i)
 {
+  /* Ensure we run the modification hooks for the right buffer,
+     without switching buffers twice (bug 36190).  FIXME: Switching
+     buffers is slow and often unnecessary.  */
+  if (BUFFERP (object) && XBUFFER (object) != current_buffer)
+    {
+      ptrdiff_t count = SPECPDL_INDEX ();
+      record_unwind_current_buffer ();
+      set_buffer_internal (XBUFFER (object));
+
+      set_text_properties_1 (start, end, properties, object, i);
+      unbind_to (count, Qnil);
+      return;
+    }
+
   INTERVAL prev_changed = NULL;
   ptrdiff_t s = XFIXNUM (start);
   ptrdiff_t len = XFIXNUM (end) - s;
@@ -1495,6 +1534,19 @@ DEFUN ("remove-text-properties", Fremove_text_properties,
 Use `set-text-properties' if you want to remove all text properties.  */)
   (Lisp_Object start, Lisp_Object end, Lisp_Object properties, Lisp_Object object)
 {
+  /* Ensure we run the modification hooks for the right buffer,
+     without switching buffers twice (bug 36190).  FIXME: Switching
+     buffers is slow and often unnecessary.  */
+  if (BUFFERP (object) && XBUFFER (object) != current_buffer)
+    {
+      ptrdiff_t count = SPECPDL_INDEX ();
+      record_unwind_current_buffer ();
+      set_buffer_internal (XBUFFER (object));
+      return unbind_to (count,
+			Fremove_text_properties (start, end, properties,
+						 object));
+    }
+
   INTERVAL i, unchanged;
   ptrdiff_t s, len;
   bool modified = false;
@@ -1607,6 +1659,20 @@ DEFUN ("remove-list-of-text-properties", Fremove_list_of_text_properties,
 Return t if any property was actually removed, nil otherwise.  */)
   (Lisp_Object start, Lisp_Object end, Lisp_Object list_of_properties, Lisp_Object object)
 {
+  /* Ensure we run the modification hooks for the right buffer,
+     without switching buffers twice (bug 36190).  FIXME: Switching
+     buffers is slow and often unnecessary.  */
+  if (BUFFERP (object) && XBUFFER (object) != current_buffer)
+    {
+      ptrdiff_t count = SPECPDL_INDEX ();
+      record_unwind_current_buffer ();
+      set_buffer_internal (XBUFFER (object));
+      return unbind_to (count,
+			Fremove_list_of_text_properties (start, end,
+							 list_of_properties,
+							 object));
+    }
+
   INTERVAL i, unchanged;
   ptrdiff_t s, len;
   bool modified = false;
-- 
2.20.1