incorrectly, refer to @ref{Undisplayable Characters}, which describes
possible problems and explains how to solve them.
+@item
+Characters from scripts whose natural ordering of text is from right
+to left are reordered for display (@pxref{Bidirectional Editing}).
+These scripts include Arabic, Hebrew, Syriac, Thaana, and a few
+others.
+
@item
You can insert non-@acronym{ASCII} characters or search for them. To do that,
you can specify an input method (@pxref{Select Input Method}) suitable
* Unibyte Mode:: You can pick one European character set
to use without multibyte characters.
* Charsets:: How Emacs groups its internal character codes.
+* Bidirectional Editing:: Support for right-to-left scripts.
@end menu
@node International Chars
point before it and type @kbd{C-u C-x =} (@pxref{International
Chars}).
+@node Bidirectional Editing
+@section Bidirectional Editing
+@cindex bidirectional editing
+@cindex right-to-left text
+
+ Emacs supports editing text written in scripts, such as Arabic and
+Hebrew, whose natural ordering of horizontal text for display is from
+right to left. However, digits and Latin text embedded in these
+scripts are still displayed left to right. It is also not uncommon to
+have small portions of text in Arabic or Hebrew embedded in otherwise
+Latin document, e.g., as comments and strings in a program source
+file. For these reasons, text that uses these scripts is actually
+@dfn{bidirectional}: a mixture of runs of left-to-right and
+right-to-left characters.
+
+ This section describes the facilities and options provided by Emacs
+for editing bidirectional text.
+
+@cindex logical order
+@cindex visual order
+ Emacs stores right-to-left and bidirectional text in the so-called
+@dfn{logical} (or @dfn{reading}) order: the buffer or string position
+of the first character you read precedes that of the next character.
+Reordering of bidirectional text into the @dfn{visual} order happens
+at display time. As result, character positions no longer increase
+monotonically with their positions on display. Emacs implements the
+Unicode Bidirectional Algorithm described in the Unicode Standard
+Annex #9, for reordering of bidirectional text for display.
+
+@vindex bidi-display-reordering
+ The buffer-local variable @code{bidi-display-reordering} controls
+whether text in the buffer is reordered for display. If its value is
+non-@code{nil}, Emacs reorders characters that have right-to-left
+directionality when they are displayed. The default value is
+@code{nil}.
+
+ Each paragraph of bidirectional text can have its own @dfn{base
+direction}, either right-to-left or left-to-right. (Paragraph
+boundaries are defined by the regular expressions
+@code{paragraph-start} and @code{paragraph-separate}, see
+@ref{Paragraphs}.) Text in left-to-right paragraphs begins at the
+left margin of the window and is truncated or continued when it
+reaches the right margin. By contrast, text in right-to-left
+paragraphs begins at the right margin and is continued or truncated at
+the left margin.
+
+@vindex bidi-paragraph-direction
+ Emacs determines the base direction of each paragraph dynamically,
+based on the text at the beginning of the paragraph. However,
+sometimes a buffer may need to force a certain base direction for its
+paragraphs. The variable @code{bidi-paragraph-direction}, if
+non-@code{nil}, disables the dynamic determination of the base
+direction, and instead forces all paragraphs in the buffer to have the
+direction specified by its buffer-local value. The value can be either
+@code{right-to-left} or @code{left-to-right}. Any other value is
+interpreted as @code{nil}.
+
+@cindex LRM
+@cindex RLM
+ Alternatively, you can control the base direction of a paragraph by
+inserting special formatting characters in front of the paragraph.
+The special character @code{RIGHT-TO-LEFT MARK}, or @sc{rlm}, forces
+the right-to-left direction on the following paragraph, while
+@code{LEFT-TO-RIGHT MARK}, or @sc{lrm} forces the left-to-right
+direction. (You can use @kbd{C-x 8 RET} to insert these characters.)
+In a GUI session, the @sc{lrm} and @sc{rlm} characters display as
+blanks.
+
+ Because characters are reordered for display, Emacs commands that
+operate in the logical order or on stretches of buffer positions may
+produce unusual effects. For example, @kbd{C-f} and @kbd{C-b}
+commands move point in the logical order, so the cursor will sometimes
+jump when point traverses reordered bidirectional text. Similarly, a
+highlighted region covering a contiguous range of character positions
+may look discontinuous if the region spans reordered text. This is
+normal and similar to behavior of other programs that support
+bidirectional text.
+
@ignore
arch-tag: 310ba60d-31ef-4ce7-91f1-f282dd57b6b3
@end ignore
LANGUAGE (NATIVE NAME) HELLO
---------------------- -----
Amharic (\e$,1O M[MmN{\e(B) \e$,1M`MKM]\e(B
-Arabic (\e,GIqjHQYdG\e(B) \e,GecjdY\e(B \e,GeGdqSdG\e(B
+Arabic \e$,1ro\e(B(\e,GGdYQHjqI\e(B) \e,GecjdY\e(B \e,GeGdqSdG\e(B
Bengali (\e$,17,7>6b727>\e(B) \e$,17(7.787M6u7>70\e(B
Braille \e$,2(3(1('('(5\e(B
Burmese (\e$,1H9HYH;H4HYrlH9HL\e(B) \e$,1H9H$HYrmH"H<HLH5HL\e(B
German (Deutsch) Guten Tag / Gr\e,A|_\e(B Gott
Greek (\e,Fekkgmij\\e(B) \e,FCei\\e(B \e,Fsar\e(B
Gujarati (\e$,19W:!9\9p9~9d: \e(B) \e$,19h9n9x:-9d:'\e(B
-Hebrew (\e,Hzixar\e(B) \e,Hylem\e(B
+Hebrew \e$,1ro\e(B(\e$,1-",q-(,y-*\e(B) \e,Hylem\e(B
Hungarian (magyar) Sz\e,Bi\e(Bp j\e,Bs\e(B napot!
Hindi (\e$,15y5\7f5B5f6 \e(B) \e$,15h5n5x6-5d6'\e(B / \e$,15h5n5x6-5U5~5p\e(B \e$,16D\e(B
Italian (italiano) Ciao / Buon giorno
;;; Local Variables:
;;; tab-width: 32
+;;; bidi-display-reordering: t
;;; End:
\f
* Changes in Emacs 24.1
++++
+** Emacs now supports display and editing of bidirectional text.
+Warning: This is still very much experimental! The existing support
+is minimal, and when it's turned on (see below), many features are
+likely to give unexpected results, or break, or even crash! Use at
+your own risk!
+
+See the node "Bidirectional Editing" in the Emacs Manual for some
+initial documentation.
+
+To turn this on in any given buffer, set the buffer-local variable
+`bidi-display-reordering' to a non-nil value. The default is nil.
+
+The buffer-local variable `bidi-paragraph-direction', if non-nil,
+forces each paragraph in the buffer to have its base direction
+according to the value of this variable. Possible values are
+`right-to-left' and `left-to-right'. If the value is nil (the
+default), Emacs determines the base direction of each paragraph from
+its text, as specified by the Unicode Bidirectional Algorithm.
+
+Reordering of bidirectional text for display in Emacs is a "Full
+bidirectionality" class implementation of the Unicode Bidirectional
+Algorithm.
+
** GTK scroll-bars are now placed on the right by default.
Use `set-scroll-bar-mode' to change this.
(mapc (lambda (pair)
(put (car pair) 'safe-local-variable (cdr pair)))
- '((buffer-read-only . booleanp) ;; C source code
- (default-directory . stringp) ;; C source code
- (fill-column . integerp) ;; C source code
- (indent-tabs-mode . booleanp) ;; C source code
- (left-margin . integerp) ;; C source code
- (no-update-autoloads . booleanp)
- (tab-width . integerp) ;; C source code
- (truncate-lines . booleanp))) ;; C source code
+ '((buffer-read-only . booleanp) ;; C source code
+ (default-directory . stringp) ;; C source code
+ (fill-column . integerp) ;; C source code
+ (indent-tabs-mode . booleanp) ;; C source code
+ (left-margin . integerp) ;; C source code
+ (no-update-autoloads . booleanp)
+ (tab-width . integerp) ;; C source code
+ (truncate-lines . booleanp) ;; C source code
+ (bidi-display-reordering . booleanp))) ;; C source code
(put 'c-set-style 'safe-local-eval-function t)
+2010-03-29 Eli Zaretskii <eliz@gnu.org>
+
+ * doc/emacs/mule.texi (International): Mention support of
+ bidirectional editing.
+ (Bidirectional Editing): New section.
+
2010-03-28 Eli Zaretskii <eliz@gnu.org>
+ * etc/HELLO: Reorder Arabic and Hebrew into logical order, and
+ insert RLM before the opening paren, to make the display more
+ reasonable. Add setting for bidi-display-reordering in the local
+ variables section.
+
+ * lisp/files.el: Make bidi-display-reordering safe variable for
+ boolean values.
+
+ * xdisp (append_glyph): If the glyph row is reversed, prepend the
+ glyph rather than appending it.
+
+ * makefile.w32-in (OBJ1): Add $(BLD)/bidi.$(O).
+ ($(BLD)/bidi.$(O)): New target.
+
* bidi.c (bidi_get_next_char_visually): Improve commentary.
* dispextern.h (PRODUCE_GLYPHS): Set the reversed_p flag in the
$(BLD)/vm-limit.$(O) \
$(BLD)/region-cache.$(O) \
$(BLD)/strftime.$(O) \
+ $(BLD)/bidi.$(O) \
$(BLD)/charset.$(O) \
$(BLD)/character.$(O) \
$(BLD)/chartab.$(O) \
$(SRC)/syssignal.h \
$(SRC)/systime.h
+$(BLD)/bidi.$(O) : \
+ $(SRC)/bidi.c \
+ $(CONFIG_H) \
+ $(SRC)/lisp.h \
+ $(SRC)/buffer.h \
+ $(SRC)/character.h \
+ $(SRC)/dispextern.h
+
$(BLD)/buffer.$(O) : \
$(SRC)/buffer.c \
$(CONFIG_H) \
++it->vpos;
++it->glyph_row;
/* The next row should use same value of the reversed_p flag as this
- one. set_iterator_to_next decides when it's a new paragraph and
- recomputes the value of the flag accordingly. */
+ one. set_iterator_to_next decides when it's a new paragraph, and
+ PRODUCE_GLYPHS recomputes the value of the flag accordingly. */
it->glyph_row->reversed_p = row->reversed_p;
it->start = row_end;
return row->displays_text_p;
glyph = it->glyph_row->glyphs[area] + it->glyph_row->used[area];
if (glyph < it->glyph_row->glyphs[area + 1])
{
+ /* If the glyph row is reversed, we need to prepend the glyph
+ rather than append it. */
+ if (it->glyph_row->reversed_p && area == TEXT_AREA)
+ {
+ struct glyph *g;
+
+ /* Make room for the additional glyph. */
+ for (g = glyph - 1; g >= it->glyph_row->glyphs[area]; g--)
+ g[1] = *g;
+ glyph = it->glyph_row->glyphs[area];
+ }
glyph->charpos = CHARPOS (it->position);
glyph->object = it->object;
if (it->pixel_width > 0)
abort ();
glyph->bidi_type = it->bidi_it.type;
}
+ else
+ {
+ glyph->resolved_level = 0;
+ glyph->bidi_type = UNKNOWN_BT;
+ }
++it->glyph_row->used[area];
}
else
projects / emacs.git / commitdiff