Weird behaviour in current Emacs master

[Lele Gaifax]

Hi all,

today I spent a few hours investigating a very strange behaviour I got
with current Emacs trunk, that I will try to explain.

Some context: at work I have an Ubuntu desktop, where I use the
https://launchpad.net/~ubuntu-elisp/+archive/ppa Emacs package, rebuilt
every day from the master repository. This morning I did update the
system because I planned to upgrade it in the evening to the just
released 14.04 version, so I got latest Emacs and used it.

In the afternoon, editing a very simple HTML snippet, the strange thing
happened. I was able to replicate it with the following very simple code
in the buffer, where "^" is the "point":

  <table>
    ^
  </table>

When I insert "<tr>", the last char (that is, ">"), triggers the strange
thing: in my case it immediately jumps to the eye because I have
hl-line-mode active, so the remaining part of the buffer is highlighted,
that is, from the end of the second line to the end of the third line,
including the "</table>" text: effectively, a C-a brings the cursor on
the first column of the second line, a C-e brings it to the end of the
third line!

I first tried to recompile Emacs by myself, with the very same
results. Then I discovered that it must be something in the minor modes
that my configuration activates, because "emacs -Q" does not exhibit the
problem. Gosh... :-(

Back at home, I was pleased to find that my installation there was
working without problems and thankfully I compiled it just a five days
ago, so I restarted the investigation. I pulled and recompiled latest
version and effectively the problem appeared. While writing this post I
then tried to bisect the problem and eventually identified it with the
following changeset:

    commit 00cbdba426ab08964ee8eae14a890945df33b595
    Author: Eli Zaretskii <address@hidden>
    Date:   Mon Apr 14 18:32:27 2014 +0300

        Fix bidirectional redisplay when deletion creates a paragraph start.

         src/insdel.c (invalidate_buffer_caches): When deleting or replacing
         text, invalidate the bidi_paragraph_cache upto and including the
         preceding newline.

The buffer is in html-mode major mode, and this is the list of activated
minor modes:

    Enabled minor modes: Auto-Composition Auto-Compression
    Auto-Encryption Auto-Fill Auto-Insert Column-Number Electric-Indent
    Electric-Pair File-Name-Shadow Flyspell Font-Lock
    Global-Auto-Complete Global-Font-Lock Hl-Line Jabber-Activity
    Line-Number Mouse-Wheel Shell-Dirtrack Show-Paren Subword
    Transient-Mark Whitespace Whitespace-Cleanup Winner Yas Yas-Global

Apparently, neither html-mode nor hl-line-mode are involved, because the
problem happens also in fundamental-mode with the latter minor disabled.

Is there anything I can do to help you understand what's going wrong? I
could try "bisecting" the activation of all those minor modes... but
maybe you have some better hint on how to proceed.

Thank you in advance for any advice,
ciao, lele.
-- 
nickname: Lele Gaifax | Quando vivrò di quello che ho pensato ieri
real: Emanuele Gaifas | comincerò ad aver paura di chi mi copia.
address@hidden  |                 -- Fortunato Depero, 1929.