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1 *rileft.txt* For Vim version 7.0aa. Last change: 2005 Apr 04
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4 VIM REFERENCE MANUAL by Avner Lottem
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5 updated by Nadim Shaikli
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6
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7
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8 Right to Left display mode for Vim *rileft*
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9
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10
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11 These functions were originally created by Avner Lottem:
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12 E-mail: alottem@iil.intel.com
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13 Phone: +972-4-8307322
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14
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15 {Vi does not have any of these commands}
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16
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17 *E26*
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18 This feature is only available when the |+rightleft| feature was enabled
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19 at compile time.
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20
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21
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22 Introduction
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23 ------------
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24 Some languages such as Arabic, Farsi, Hebrew (among others) require the
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25 ability to display their text from right-to-left. Files in those languages
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26 are stored conventionally and the right-to-left requirement is only a
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27 function of the display engine (per the Unicode specification). In
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28 right-to-left oriented files the characters appear on the screen from
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29 right to left.
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30
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31 Bidirectionality (or bidi for short) is what Unicode offers as a full
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32 solution to these languages. Bidi offers the user the ability to view
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33 both right-to-left as well as left-to-right text properly at the same time
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34 within the same window. Vim currently, due to simplicity, does not offer
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35 bidi and is merely opting to present a functional means to display/enter/use
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36 right-to-left languages. An older hybrid solution in which direction is
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37 encoded for every character (or group of characters) are not supported either
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38 as this kind of support is out of the scope of a simple addition to an
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39 existing editor (and it's not sanctioned by Unicode either).
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40
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41
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42 Highlights
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43 ----------
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44 o Editing left-to-right files as in the original Vim, no change.
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45
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46 o Viewing and editing files in right-to-left windows. File orientation
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47 is per window, so it is possible to view the same file in right-to-left
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48 and left-to-right modes, simultaneously. (Useful for editing mixed files
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49 in which both right-to-left and left-to-right text exist).
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50
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51 o Compatibility to the original Vim. Almost all features work in
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52 right-to-left mode (see Bugs below).
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53
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54 o Backing from reverse insert mode to the correct place in the file
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55 (if possible).
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56
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57 o No special terminal with right-to-left capabilities is required. The
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58 right-to-left changes are completely hardware independent.
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59
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60 o Many languages use and require right-to-left support. These languages
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61 can quite easily be supported given the inclusion of their required
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62 keyboard mappings and some possible minor code change. Some of the
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63 current supported languages include - |arabic.txt|, |farsi.txt| and
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64 |hebrew.txt|.
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65
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66
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67 Of Interest...
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68 --------------
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69
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70 o Invocations
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71 -----------
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72 + 'rightleft' ('rl') sets window orientation to right-to-left.
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73 + 'delcombine' ('deco'), boolean, if editing UTF-8 encoded languages,
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74 allows one to remove a composing character which gets superimposed
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75 on those that proceeded them (some languages require this).
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76 + 'rightleftcmd' ('rlc') sets the command-line within certain modes
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77 (such as search) to be utilized in right-to-left orientation as well.
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78
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79 o Typing backwards *ins-reverse*
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80 ----------------
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81 In lieu of using full-fledged the 'rightleft' option, one can opt for
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82 reverse insertion. When the 'revins' (reverse insert) option is set,
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83 inserting happens backwards. This can be used to type right-to-left
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84 text. When inserting characters the cursor is not moved and the text
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85 moves rightwards. A <BS> deletes the character under the cursor.
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86 CTRL-W and CTRL-U also work in the opposite direction. <BS>, CTRL-W
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87 and CTRL-U do not stop at the start of insert or end of line, no matter
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88 how the 'backspace' option is set.
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89
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90 There is no reverse replace mode (yet).
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91
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92 If the 'showmode' option is set, "-- REVERSE INSERT --" will be shown
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93 in the status line when reverse Insert mode is active.
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94
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95 o Pasting when in a rightleft window
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96 ----------------------------------
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97 When cutting text with the mouse and pasting it in a rightleft window
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98 the text will be reversed, because the characters come from the cut buffer
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99 from the left to the right, while inserted in the file from the right to
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100 the left. In order to avoid it, toggle 'revins' before pasting.
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101
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102
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103 Bugs
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104 ----
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105 o Does not handle CTRL-A and CTRL-X commands (add and subtract) correctly
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106 when in rightleft window.
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107
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108 o Does not support reverse insert and rightleft modes on the command-line.
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109 However, functionality of the editor is not reduced, because it is
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110 possible to enter mappings, abbreviations and searches typed from the
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111 left to the right on the command-line.
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112
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113 o Somewhat slower in right-to-left mode, because right-to-left motion is
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114 emulated inside Vim, not by the controlling terminal.
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115
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116 o When the Athena GUI is used, the bottom scrollbar works in the wrong
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117 direction. This is difficult to fix.
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118
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119 o When both 'rightleft' and 'revins' are on: 'textwidth' does not work.
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120 Lines do not wrap at all; you just get a single, long line.
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121
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122 o There is no full bidirectionality (bidi) support.
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123
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124
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125 vim:tw=78:ts=8:ft=help:norl:
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