bug#17905: 24.3.50; writing with a giant font triggers RTL text entry

[Eli Zaretskii <eliz@gnu.org>]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: Eli Zaretskii <eliz@gnu.org>, 17905@debbugs.gnu.org
> Date: Thu, 03 Jul 2014 09:51:29 -0400
> 
> >> - start with "emacs -Q"
> >> - enlarge the font by shift-mouse and selecting "Increase Buffer
> >> Text Size" N times (please tell what is the value of N)
> >> - type the following text: ....
> 
> > ... where N=12 was a value that triggered the effect for me.  Also
> > note that the Emacs window was full-screen.
> 
> Ah, yes, I can reproduce it:

I can't.

> it's not RTL-rendering.
> It's some issue with cursor positioning, such that after some
> line-wrapping, when you enter a char, somehow point ends up before the
> new char rather than after, so you end up typing "backwards".

Are you saying that completely redisplaying the window (e.g., with
"C-x 0" followed by "C-x b THAT-BUFFER RET") makes the display correct
again?  I guess not, in which case this is not about _cursor_
positioning, but rather about _point_ positioning.  Right?

Anyway, since Joe complicated the recipe with going full-screen (which
makes everything dependent on the monitor dimensions), I would ask you
two to answer the following questions:

  - Can the issue be reproduced without enlarging the font?

  - Does the issue happen only in continuation lines?  If so, does it
    happen as soon as the line is continued, or do you have to have
    several continuation lines?

  - Stefan, did you see it on the emacs-24 branch or on the trunk (or
    both)?

  - Is it important what text to type, or will any text do?

(I cannot reproduce this no matter what I do.  I'm tempted to say it's
X-specific, but I fail to see how could it be.)