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116 lines
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116 lines
4.6 KiB
Plaintext
*rileft.txt* For Vim version 7.4. Last change: 2006 Apr 24
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VIM REFERENCE MANUAL by Avner Lottem
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updated by Nadim Shaikli
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Right to Left display mode for Vim *rileft*
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These functions were originally created by Avner Lottem:
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E-mail: alottem@iil.intel.com
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Phone: +972-4-8307322
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Introduction
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------------
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Some languages such as Arabic, Farsi, Hebrew (among others) require the
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ability to display their text from right-to-left. Files in those languages
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are stored conventionally and the right-to-left requirement is only a
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function of the display engine (per the Unicode specification). In
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right-to-left oriented files the characters appear on the screen from
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right to left.
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Bidirectionality (or bidi for short) is what Unicode offers as a full
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solution to these languages. Bidi offers the user the ability to view
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both right-to-left as well as left-to-right text properly at the same time
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within the same window. Vim currently, due to simplicity, does not offer
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bidi and is merely opting to present a functional means to display/enter/use
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right-to-left languages. An older hybrid solution in which direction is
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encoded for every character (or group of characters) are not supported either
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as this kind of support is out of the scope of a simple addition to an
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existing editor (and it's not sanctioned by Unicode either).
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Highlights
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----------
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o Editing left-to-right files as in the original Vim, no change.
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o Viewing and editing files in right-to-left windows. File orientation
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is per window, so it is possible to view the same file in right-to-left
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and left-to-right modes, simultaneously. (Useful for editing mixed files
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in which both right-to-left and left-to-right text exist).
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o Compatibility to the original Vim. Almost all features work in
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right-to-left mode (see Bugs below).
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o Backing from reverse insert mode to the correct place in the file
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(if possible).
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o No special terminal with right-to-left capabilities is required. The
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right-to-left changes are completely hardware independent.
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o Many languages use and require right-to-left support. These languages
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can quite easily be supported given the inclusion of their required
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keyboard mappings and some possible minor code change. Some of the
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current supported languages include - |arabic.txt|, |farsi.txt| and
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|hebrew.txt|.
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Of Interest...
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--------------
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o Invocations
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-----------
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+ 'rightleft' ('rl') sets window orientation to right-to-left.
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+ 'delcombine' ('deco'), boolean, if editing UTF-8 encoded languages,
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allows one to remove a composing character which gets superimposed
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on those that proceeded them (some languages require this).
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+ 'rightleftcmd' ('rlc') sets the command-line within certain modes
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(such as search) to be utilized in right-to-left orientation as well.
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o Typing backwards *ins-reverse*
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----------------
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In lieu of using full-fledged the 'rightleft' option, one can opt for
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reverse insertion. When the 'revins' (reverse insert) option is set,
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inserting happens backwards. This can be used to type right-to-left
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text. When inserting characters the cursor is not moved and the text
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moves rightwards. A <BS> deletes the character under the cursor.
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CTRL-W and CTRL-U also work in the opposite direction. <BS>, CTRL-W
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and CTRL-U do not stop at the start of insert or end of line, no matter
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how the 'backspace' option is set.
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There is no reverse replace mode (yet).
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If the 'showmode' option is set, "-- REVERSE INSERT --" will be shown
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in the status line when reverse Insert mode is active.
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o Pasting when in a rightleft window
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----------------------------------
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When cutting text with the mouse and pasting it in a rightleft window
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the text will be reversed, because the characters come from the cut buffer
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from the left to the right, while inserted in the file from the right to
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the left. In order to avoid it, toggle 'revins' before pasting.
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Bugs
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----
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o Does not handle CTRL-A and CTRL-X commands (add and subtract) correctly
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when in rightleft window.
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o Does not support reverse insert and rightleft modes on the command-line.
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However, functionality of the editor is not reduced, because it is
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possible to enter mappings, abbreviations and searches typed from the
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left to the right on the command-line.
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o Somewhat slower in right-to-left mode, because right-to-left motion is
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emulated inside Vim, not by the controlling terminal.
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o When both 'rightleft' and 'revins' are on: 'textwidth' does not work.
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Lines do not wrap at all; you just get a single, long line.
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o There is no full bidirectionality (bidi) support.
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vim:tw=78:ts=8:ft=help:norl:
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