rightleft.txt - html version

rightleft.txt - html version


*rightleft.txt* For Vim version 5.3.  Last modification: 1998 Aug 17


		  VIM REFERENCE MANUAL    by Avner Lottem




Right to Left and Hebrew Mapping for Vim		*hebrew*


These functions have been made by Avner Lottem
E-mail: <alottem@iil.intel.com>
Phone:  +972-4-8307322

{Vi does not have any of these commands}

All this is only available when the |+rightleft| feature was enabled at
compile time.


Introduction
In right-to-left oriented files the characters appear on the screen from right
to left.  This kind of file is most useful when writing Hebrew documents using
TeX--XeT, troffh, composing faxes or writing Hebrew memos.

Logical order files, where direction is encoded for every character (or group
of characters) are not supported as this kind of support is out of the scope
of a simple addition to an existing editor.  Also, no Hebrew commands, prompts
and help files were added, the standard Vi interface was maintained.  The
intension here was to incorporate Hebrew support to an existing modern and
live editor, hoping that the Hebrew support will continue to live in
subsequent versions.  Many other Hebrew supported packages were designed for a
particular version of the original (English) software and when it continued
developing, the Hebrew version stayed behind.  Therefore this particular
support to Vim tries to be as simple (and short) as possible, so that it could
be incorporated into the official source.


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.
   (This is sometimes useful when editing documents with TeX--XeT.)

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

o  Changing keyboard mapping and reverse insert modes using a single
   command.

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.  Only
   Hebrew font is necessary.

   The MIT X distribution includes at least two fonts: heb6x13 and heb8x13.
   Some fonts are on sunsite.unc.edu: /pub/Linux/X11/fonts/hebxfonts-0.2.tgz.
   More pointers are in the Hebrew HOWTO on sunsite: /pub/Linux/docs/HOWTO.
   To create a Hebrew font for a DOS box under MS-Windows, refer to a hack on
   ftp://tochna.technion.ac.il/pub/staff/lottem/doswin-0.1.tgz.

o  It should be quite easy to adjust this support to handle other right-to
   left languages, such as Arabic, by simply changing the keyboard mapping
   according to the character encoding.


Change details
+  Variables:
   +  rightleft (rl) sets window orientation to right-to-left.
   +  hkmap (hk) sets keyboard mapping to Hebrew, in insert/replace modes.
   +  aleph (al), numeric, holds the decimal code of Aleph, for keyboard
      mapping.

+  Encoding:
   +  Under Unix, ISO 8859-8 encoding (Hebrew letters codes: 224-250).
   +  Under MS DOS, PC encoding (Hebrew letters codes: 128-154).
   These are defaults, that can be overided using the aleph variable.

+  Vim arguments:
   +  'vim -H file' starts editing a Hebrew file, i.e. rightleft and hkmap
      are set.

+  Keyboard:
   +  The 'allowrevins' option enables the CTRL-_ command in Insert mode and
      in Command-line mode.

   +  CTRL-_ in insert/replace modes toggles revins and hkmap as follows:

      When in rightleft window, revins+nohkmap are toggled, since English
      will likely be inserted in this case.

      When in norightleft window, revins+hkmap are toggled, since Hebrew
      will likely be inserted in this case.

      CTRL-_ moves the cursor to the end of the typed text.

   +  CTRL-_ in command mode only toggles keyboard mapping (see Bugs below).
      This setting is independent of hkmap variable, which only applies to
      insert/replace mode.

      Note: On some keyboards, CTRL-_ is mapped to CTRL-?.

   +  Keyboard mapping while hkmap is set:

	q w e r t y u i o p		The characters in the mapping shown
	/ ''        		here are for ISO 8859-8.

	 a s d f g h j k l ; ''
	           ,

	  z x c v b n m , . /
	           .


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 with Hebrew text,
   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  Does not support 7 bit terminals.  Only a terminal with complete
   Hebrew English font (without need to send escape sequences to switch
   between Hebrew and English) is supported.

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.




Typing backwards					*ins-reverse*

If the 'revins' (reverse insert) option is set, inserting happens backwards.
This can be used to type Hebrew.  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.

When the 'allowrevins' option is set, reverse Insert mode can be also entered
via CTRL-_, which has some extra functionality: First, keyboard mapping is
changed according to the window orientation -- if in a left-to-right window,
revins is used to enter Hebrew text, so the keyboard changes to Hebrew (hkmap
is set); if in a right-to-left window, revins is used to enter English text,
so the keyboard changes to English (hkmap is reset).  Second, when exiting
revins via CTRL-_, the cursor moves to the end of the typed text (if
possible).


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 (by typing CTRL-? or CTRL-_)
before pasting.

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