1*rileft.txt*    For Vim version 7.3.  Last change: 2006 Apr 24
2
3
4		  VIM REFERENCE MANUAL    by Avner Lottem
5					  updated by Nadim Shaikli
6
7
8Right to Left display mode for Vim				*rileft*
9
10
11These functions were originally created by Avner Lottem:
12   E-mail: alottem@iil.intel.com
13   Phone:  +972-4-8307322
14
15{Vi does not have any of these commands}
16
17								*E26*
18{only available when compiled with the |+rightleft| feature}
19
20
21Introduction
22------------
23Some languages such as Arabic, Farsi, Hebrew (among others) require the
24ability to display their text from right-to-left.  Files in those languages
25are stored conventionally and the right-to-left requirement is only a
26function of the display engine (per the Unicode specification).  In
27right-to-left oriented files the characters appear on the screen from
28right to left.
29
30Bidirectionality (or bidi for short) is what Unicode offers as a full
31solution to these languages.  Bidi offers the user the ability to view
32both right-to-left as well as left-to-right text properly at the same time
33within the same window.  Vim currently, due to simplicity, does not offer
34bidi and is merely opting to present a functional means to display/enter/use
35right-to-left languages.  An older hybrid solution in which direction is
36encoded for every character (or group of characters) are not supported either
37as this kind of support is out of the scope of a simple addition to an
38existing editor (and it's not sanctioned by Unicode either).
39
40
41Highlights
42----------
43o  Editing left-to-right files as in the original Vim, no change.
44
45o  Viewing and editing files in right-to-left windows.  File orientation
46   is per window, so it is possible to view the same file in right-to-left
47   and left-to-right modes, simultaneously.  (Useful for editing mixed files
48   in which both right-to-left and left-to-right text exist).
49
50o  Compatibility to the original Vim.  Almost all features work in
51   right-to-left mode (see Bugs below).
52
53o  Backing from reverse insert mode to the correct place in the file
54   (if possible).
55
56o  No special terminal with right-to-left capabilities is required.  The
57   right-to-left changes are completely hardware independent.
58
59o  Many languages use and require right-to-left support.  These languages
60   can quite easily be supported given the inclusion of their required
61   keyboard mappings and some possible minor code change.  Some of the
62   current supported languages include - |arabic.txt|, |farsi.txt| and
63   |hebrew.txt|.
64
65
66Of Interest...
67--------------
68
69o  Invocations
70   -----------
71   + 'rightleft' ('rl') sets window orientation to right-to-left.
72   + 'delcombine' ('deco'), boolean, if editing UTF-8 encoded languages,
73     allows one to remove a composing character which gets superimposed
74     on those that proceeded them (some languages require this).
75   + 'rightleftcmd' ('rlc') sets the command-line within certain modes
76     (such as search) to be utilized in right-to-left orientation as well.
77
78o  Typing backwards					*ins-reverse*
79   ----------------
80   In lieu of using full-fledged the 'rightleft' option, one can opt for
81   reverse insertion.  When the 'revins' (reverse insert) option is set,
82   inserting happens backwards.  This can be used to type right-to-left
83   text.  When inserting characters the cursor is not moved and the text
84   moves rightwards.  A <BS> deletes the character under the cursor.
85   CTRL-W and CTRL-U also work in the opposite direction.  <BS>, CTRL-W
86   and CTRL-U do not stop at the start of insert or end of line, no matter
87   how the 'backspace' option is set.
88
89   There is no reverse replace mode (yet).
90
91   If the 'showmode' option is set, "-- REVERSE INSERT --" will be shown
92   in the status line when reverse Insert mode is active.
93
94o  Pasting when in a rightleft window
95   ----------------------------------
96   When cutting text with the mouse and pasting it in a rightleft window
97   the text will be reversed, because the characters come from the cut buffer
98   from the left to the right, while inserted in the file from the right to
99   the left.   In order to avoid it, toggle 'revins' before pasting.
100
101
102Bugs
103----
104o  Does not handle CTRL-A and CTRL-X commands (add and subtract) correctly
105   when in rightleft window.
106
107o  Does not support reverse insert and rightleft modes on the command-line.
108   However, functionality of the editor is not reduced, because it is
109   possible to enter mappings, abbreviations and searches typed from the
110   left to the right on the command-line.
111
112o  Somewhat slower in right-to-left mode, because right-to-left motion is
113   emulated inside Vim, not by the controlling terminal.
114
115o  When the Athena GUI is used, the bottom scrollbar works in the wrong
116   direction.  This is difficult to fix.
117
118o  When both 'rightleft' and 'revins' are on: 'textwidth' does not work.
119   Lines do not wrap at all; you just get a single, long line.
120
121o  There is no full bidirectionality (bidi) support.
122
123
124 vim:tw=78:ts=8:ft=help:norl:
125