characters, as well as many non-@acronym{ASCII} characters.
@vindex tab-width
-@cindex control character
+@cindex control characters on display
The @acronym{ASCII} character set contains non-printing @dfn{control
characters}. Two of these are displayed specially: the newline
character (Unicode code point @code{U+000A}) is displayed by starting
in the buffer is displayed has nothing to do with the definition of
@key{TAB} as a command.
- Other @acronym{ASCII} control characters are displayed as a caret
+ Other @acronym{ASCII} control characters, whose codes are below
+@code{U+0020} (octal 40, decimal 32), are displayed as a caret
(@samp{^}) followed by the non-control version of the character, with
the @code{escape-glyph} face. For instance, the @samp{control-A}
character, @code{U+0001}, is displayed as @samp{^A}.
+@cindex octal escapes
@vindex ctl-arrow
- The non-@acronym{ASCII}, non-printing characters @code{U+0080}
-(octal 200) through @code{U+009F} (octal 237) are displayed as octal
-escape sequences, with the @code{escape-glyph} face. For instance,
+ The raw bytes with codes @code{U+0080} (octal 200) through
+@code{U+009F} (octal 237) are displayed as @dfn{octal escape
+sequences}, with the @code{escape-glyph} face. For instance,
character code @code{U+0098} (octal 230) is displayed as @samp{\230}.
If you change the buffer-local variable @code{ctl-arrow} to
-@code{nil}, @acronym{ASCII} control characters are also displayed as
-octal escape sequences instead of caret escape sequences.
+@code{nil}, the @acronym{ASCII} control characters are also displayed
+as octal escape sequences instead of caret escape sequences.
@vindex nobreak-char-display
@cindex non-breaking space
On graphical displays, some characters may have no glyphs in any of
the fonts available to Emacs. These @dfn{glyphless characters} are
normally displayed as boxes containing the hexadecimal character code.
-You can control the display method by customizing the variable
-@code{glyphless-char-display-control}. @xref{Glyphless Chars,,
-Glyphless Character Display, elisp, The Emacs Lisp Reference Manual},
-for details.
+Similarly, on text terminals, characters that cannot be displayed
+using the terminal encoding (@pxref{Terminal Coding}) are normally
+displayed as question signs. You can control the display method by
+customizing the variable @code{glyphless-char-display-control}.
+@xref{Glyphless Chars,, Glyphless Character Display, elisp, The Emacs
+Lisp Reference Manual}, for details.
@node Cursor Display
@section Displaying the Cursor
@itemize @bullet
@item
Character codes 32 through 126 map to glyph codes 32 through 126.
-Normally this means they display as themselves.
+Normally this means they display as themselves, but a display table
+can change that.
@item
Character code 9 is a horizontal tab. It displays as whitespace
up to a position determined by @code{tab-width}.
@item
-Character code 10 is a newline.
+Character code 10 is a newline. It is normally invisible on display,
+and has the effect of ending the preceding line and starting a new
+line.
@item
-All other codes in the range 0 through 31, and code 127, display in one
-of two ways according to the value of @code{ctl-arrow}. If it is
-non-@code{nil}, these codes map to sequences of two glyphs, where the
-first glyph is the @acronym{ASCII} code for @samp{^}. (A display table can
-specify a glyph to use instead of @samp{^}.) Otherwise, these codes map
-just like the codes in the range 128 to 255.
-
-On MS-DOS terminals, Emacs arranges by default for the character code
-127 to be mapped to the glyph code 127, which normally displays as an
-empty polygon. This glyph is used to display non-@acronym{ASCII} characters
-that the MS-DOS terminal doesn't support. @xref{MS-DOS and MULE,,,
-emacs, The GNU Emacs Manual}.
-
+All other codes in the range 0 through 31 display in one of two ways
+according to the value of @code{ctl-arrow}. If it is non-@code{nil},
+these codes map to sequences of two glyphs, where the first glyph is
+the @acronym{ASCII} code for @samp{^}. (A display table can specify a
+glyph to use instead of @samp{^}.) Otherwise, these codes map just
+like the raw bytes in the range 128 to 255 (described below).
+
+@cindex octal escapes
@item
-Character codes 128 through 255 map to sequences of four glyphs, where
-the first glyph is the @acronym{ASCII} code for @samp{\}, and the others are
-digit characters representing the character code in octal. (A display
-table can specify a glyph to use instead of @samp{\}.)
+Raw bytes (@pxref{Text Representations}) with codes 128 through 255,
+and the @acronym{ASCII} control character with code 127, display as
+sequences of four glyphs, where the first glyph is the @acronym{ASCII}
+code for @samp{\}, and the others are digit characters representing
+the character code in octal. (A display table can specify a glyph to
+use instead of @samp{\}.) This is known as the @dfn{octal escape}
+display.
@item
-Multibyte character codes above 256 are displayed as themselves, or as
-a question mark or a hex code or an empty box if the terminal cannot
-display that character.
+Non-@acronym{ASCII} character codes above 127 are displayed as
+themselves, if the terminal and the available fonts support them.
+Characters that are not supported by the terminal, or (on window
+systems) have no fonts available for them, are displayed as a question
+mark or a hex code or an empty box. @xref{Glyphless Chars}, for how
+to control display of the characters not supported by the terminal or
+fonts. Display tables can change how a character is displayed, even
+if it is supported.
@end itemize
The usual display conventions apply even when there is a display
This buffer-local variable controls how control characters are
displayed. If it is non-@code{nil}, they are displayed as a caret
followed by the character: @samp{^A}. If it is @code{nil}, they are
-displayed as a backslash followed by three octal digits: @samp{\001}.
+displayed as octal escapes: a backslash followed by three octal
+digits, as in @samp{\001}.
@end defopt
@defopt tab-width
HCoop / bpt / emacs.git / commitdiff