VIM: rileft

## RILEFT

    *rileft.txt*    For Vim version 8.2.  Last change: 2021 Jun 13

    		  VIM REFERENCE MANUAL    by Avner Lottem
    					  updated by Nadim Shaikli

    Right to Left display mode for Vim				*rileft*

    These functions were originally created by Avner Lottem:
       E-mail: alottem@iil.intel.com
       Phone:  +972-4-8307322

    								*E26*
    {only available when compiled with the |+rightleft| feature}

    Introduction

    Some languages such as Arabic, Farsi, Hebrew (among others) require the
    ability to display their text from right-to-left.  Files in those languages
    are stored conventionally and the right-to-left requirement is only a
    function of the display engine (per the Unicode specification).  In
    right-to-left oriented files the characters appear on the screen from
    right to left.

    Bidirectionality (or bidi for short) is what Unicode offers as a full
    solution to these languages.  Bidi offers the user the ability to view
    both right-to-left as well as left-to-right text properly at the same time
    within the same window.  Vim currently, due to simplicity, does not offer
    bidi and is merely opting to present a functional means to display/enter/use
    right-to-left languages.  An older hybrid solution in which direction is
    encoded for every character (or group of characters) are not supported either
    as this kind of support is out of the scope of a simple addition to an
    existing editor (and it's not sanctioned by Unicode either).

    Highlights

    o  Editing left-to-right files as in the original Vim, no change.

    o  Viewing and editing files in right-to-left windows.  File orientation
       is per window, so it is possible to view the same file in right-to-left
       and left-to-right modes, simultaneously.  (Useful for editing mixed files
       in which both right-to-left and left-to-right text exist).

    o  Compatibility to the original Vim.  Almost all features work in
       right-to-left mode (see Bugs below).

    o  Backing from reverse insert mode to the correct place in the file
       (if possible).

    o  No special terminal with right-to-left capabilities is required.  The
       right-to-left changes are completely hardware independent.

    o  Many languages use and require right-to-left support.  These languages
       can quite easily be supported given the inclusion of their required
       keyboard mappings and some possible minor code change.  Some of the
       current supported languages include - |arabic|, |farsi| and
       |hebrew|.

    Of Interest...

    o  Invocations

       + 'rightleft' ('rl') sets window orientation to right-to-left.
       + 'delcombine' ('deco'), boolean, if editing UTF-8 encoded languages,
         allows one to remove a composing character which gets superimposed
         on those that preceded them (some languages require this).
       + 'rightleftcmd' ('rlc') sets the command-line within certain modes
         (such as search) to be utilized in right-to-left orientation as well.

    o  Typing backwards					*ins-reverse*

       In lieu of using the full-fledged 'rightleft' option, one can opt for
       reverse insertion.  When the 'revins' (reverse insert) option is set,
       inserting happens backwards.  This can be used to type right-to-left
       text.  When inserting characters the cursor is not moved and the text
       moves rightwards.  A <BS> deletes the character under the cursor.
       CTRL-W and CTRL-U also work in the opposite direction.  <BS>, CTRL-W
       and CTRL-U do not stop at the start of insert or end of line, no matter
       how the 'backspace' option is set.

       There is no reverse replace mode (yet).

       If the 'showmode' option is set, "-- REVERSE INSERT --" will be shown
       in the status line when reverse Insert mode is active.

    o  Pasting when in a rightleft window

       When cutting text with the mouse and pasting it in a rightleft window
       the text will be reversed, because the characters come from the cut buffer
       from the left to the right, while inserted in the file from the right to
       the left.   In order to avoid it, toggle 'revins' before pasting.

    Bugs

    o  Does not handle CTRL-A and CTRL-X commands (add and subtract) correctly
       when in rightleft window.

    o  Does not support reverse insert and rightleft modes on the command-line.
       However, functionality of the editor is not reduced, because it is
       possible to enter mappings, abbreviations and searches typed from the
       left to the right on the command-line.

    o  Somewhat slower in right-to-left mode, because right-to-left motion is
       emulated inside Vim, not by the controlling terminal.

    o  When the Athena GUI is used, the bottom scrollbar works in the wrong
       direction.  This is difficult to fix.

    o  When both 'rightleft' and 'revins' are on: 'textwidth' does not work.
       Lines do not wrap at all; you just get a single, long line.

    o  There is no full bidirectionality (bidi) support.

     vim:tw=78:ts=8:noet:ft=help:norl:

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