bug#18277: 24.3.93; A problem with positioning point in horizontally scrolled bidirectional text

[Eli Zaretskii]

> Date: Sat, 16 Aug 2014 11:27:09 +0200
> From: martin rudalics <rudalics@gmx.at>
> 
> C-u C-h t hebrew RET
> 
> split the root window via C-x 3, provoke a horizontal scroll of the left
> window by, for example, moving the window's point to the left, move
> point of the left window to the "I" of the L2R string EDIT on line 4 and
> move my mouse cursor to the according screen position.  At this moment,
> my Emacs frame appears as in the first attached screenshot
> (mouse-click-ante.png).
> 
> Now I try to do `mouse-set-point' by doing <mouse-1>.  The left window
> scrolls horizontally back to the position it had before the previous
> horizontal scroll and the window's point moves to another position on
> the same line as in the second attached screenshot
> (mouse-click-post.png).

Fixed in revision 117446 on the emacs-24 branch.

It was a thinko in how the X coordinate was mirrored for R2L lines
that are hscrolled.