bug#62606: [PATCH] function to align mode-line elements to right

[Eli Zaretskii <eliz@gnu.org>]

> Cc: 62606@debbugs.gnu.org
> Date: Fri, 09 Jun 2023 12:03:02 -0400
> From:  Stefan Monnier via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> [ And now I wonder: can Emacs have R2L modelines?  If so, what should
>   happen in those?  ]

We don't support that.  From display_mode_line:

  /* FIXME: This should be controlled by a user option.  But
     supporting such an option is not trivial, since the mode line is
     made up of many separate strings.  */
  it.paragraph_embedding = L2R;

and a more complete rationale in redisplay_tool_bar:

  /* FIXME: This should be controlled by a user option.  But it
     doesn't make sense to have an R2L tool bar if the menu bar cannot
     be drawn also R2L, and making the menu bar R2L is tricky due
     toolkit-specific code that implements it.  If an R2L tool bar is
     ever supported, display_tool_bar_line should also be augmented to
     call unproduce_glyphs like display_line and display_string
     do.  */

Bottom line: Emacs doesn't support making the UI right-to-left.
IMNSHO in IME, supporting that would be a lot of work for very little
benefit.