configurable

Signed-off-by: shenwenjie <shenwenjie@sensetime.com>

doc/rileft.txt

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+*rileft.txt*    For Vim version 7.4.  Last change: 2006 Apr 24
+
+
+		  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
+
+{Vi does not have any of these commands}
+
+								*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.txt|, |farsi.txt| and
+   |hebrew.txt|.
+
+
+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 proceeded 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 full-fledged the '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:ft=help:norl: