Commit 483ab230 authored by Chong Yidong's avatar Chong Yidong
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More updates to Text chapter of Lisp manual.

* doc/lispref/text.texi (Mode-Specific Indent): Document new behavior of
indent-for-tab-command.  Document tab-always-indent.
(Special Properties): Copyedits.
(Checksum/Hash): Improve secure-hash doc.  Do not recommend MD5.
(Parsing HTML/XML): Rename from Parsing HTML.  Update doc of
libxml-parse-html-region.
parent d9507ec5
2012-03-08 Chong Yidong <cyd@gnu.org>
* text.texi (Mode-Specific Indent): Document new behavior of
indent-for-tab-command. Document tab-always-indent.
(Special Properties): Copyedits.
(Checksum/Hash): Improve secure-hash doc. Do not recommend MD5.
(Parsing HTML/XML): Rename from Parsing HTML. Update doc of
libxml-parse-html-region.
2012-03-07 Glenn Morris <rgm@gnu.org>
* markers.texi (The Region): Briefly mention use-empty-active-region
......
......@@ -1054,7 +1054,8 @@ Text
* Registers:: How registers are implemented. Accessing
the text or position stored in a register.
* Base 64:: Conversion to or from base 64 encoding.
* Checksum/Hash:: Computing "message digests"/"checksums"/"hashes".
* Checksum/Hash:: Computing cryptographic hashes.
* Parsing HTML/XML:: Parsing HTML and XML.
* Atomic Changes:: Installing several buffer changes "atomically".
* Change Hooks:: Supplying functions to be run when text is changed.
......
......@@ -56,8 +56,8 @@ the character after point.
* Registers:: How registers are implemented. Accessing the text or
position stored in a register.
* Base 64:: Conversion to or from base 64 encoding.
* Checksum/Hash:: Computing "message digests"/"checksums"/"hashes".
* Parsing HTML:: Parsing HTML and XML.
* Checksum/Hash:: Computing cryptographic hashes.
* Parsing HTML/XML:: Parsing HTML and XML.
* Atomic Changes:: Installing several buffer changes "atomically".
* Change Hooks:: Supplying functions to be run when text is changed.
@end menu
......@@ -2203,14 +2203,48 @@ key to indent properly for the language being edited. This section
describes the mechanism of the @key{TAB} key and how to control it.
The functions in this section return unpredictable values.
@defvar indent-line-function
This variable's value is the function to be used by @key{TAB} (and
various commands) to indent the current line. The command
@code{indent-according-to-mode} does little more than call this function.
@deffn Command indent-for-tab-command &optional rigid
This is the command bound to @key{TAB} in most editing modes. Its
usual action is to indent the current line, but it can alternatively
insert a tab character or indent a region.
Here is what it does:
In Lisp mode, the value is the symbol @code{lisp-indent-line}; in C
mode, @code{c-indent-line}; in Fortran mode, @code{fortran-indent-line}.
The default value is @code{indent-relative}. @xref{Auto-Indentation}.
@itemize
@item
First, it checks whether Transient Mark mode is enabled and the region
is active. If so, it called @code{indent-region} to indent all the
text in the region (@pxref{Region Indent}).
@item
Otherwise, if the indentation function in @code{indent-line-function}
is @code{indent-to-left-margin} (a trivial command that inserts a tab
character), or if the variable @code{tab-always-indent} specifies that
a tab character ought to be inserted (see below), then it inserts a
tab character.
@item
Otherwise, it indents the current line; this is done by calling the
function in @code{indent-line-function}. If the line is already
indented, and the value of @code{tab-always-indent} is @code{complete}
(see below), it tries completing the text at point.
@end itemize
If @var{rigid} is non-@code{nil} (interactively, with a prefix
argument), then after this command indents a line or inserts a tab, it
also rigidly indents the entire balanced expression which starts at
the beginning of the current line, in order to reflect the new
indentation. This argument is ignored if the command indents the
region.
@end deffn
@defvar indent-line-function
This variable's value is the function to be used by
@code{indent-for-tab-command}, and various other indentation commands,
to indent the current line. It is usually assigned by the major mode;
for instance, Lisp mode sets it to @code{lisp-indent-line}, C mode
sets it to @code{c-indent-line}, and so on. The default value is
@code{indent-relative}. @xref{Auto-Indentation}.
@end defvar
@deffn Command indent-according-to-mode
......@@ -2218,41 +2252,31 @@ This command calls the function in @code{indent-line-function} to
indent the current line in a way appropriate for the current major mode.
@end deffn
@deffn Command indent-for-tab-command &optional rigid
This command calls the function in @code{indent-line-function} to
indent the current line; however, if that function is
@code{indent-to-left-margin}, @code{insert-tab} is called instead.
(That is a trivial command that inserts a tab character.) If
@var{rigid} is non-@code{nil}, this function also rigidly indents the
entire balanced expression that starts at the beginning of the current
line, to reflect change in indentation of the current line.
@end deffn
@deffn Command newline-and-indent
This function inserts a newline, then indents the new line (the one
following the newline just inserted) according to the major mode.
It does indentation by calling the current @code{indent-line-function}.
In programming language modes, this is the same thing @key{TAB} does,
but in some text modes, where @key{TAB} inserts a tab,
@code{newline-and-indent} indents to the column specified by
@code{left-margin}.
following the newline just inserted) according to the major mode. It
does indentation by calling @code{indent-according-to-mode}.
@end deffn
@deffn Command reindent-then-newline-and-indent
@comment !!SourceFile simple.el
This command reindents the current line, inserts a newline at point,
and then indents the new line (the one following the newline just
inserted).
This command does indentation on both lines according to the current
major mode, by calling the current value of @code{indent-line-function}.
In programming language modes, this is the same thing @key{TAB} does,
but in some text modes, where @key{TAB} inserts a tab,
@code{reindent-then-newline-and-indent} indents to the column specified
by @code{left-margin}.
inserted). It does indentation on both lines by calling
@code{indent-according-to-mode}.
@end deffn
@defopt tab-always-indent
This variable can be used to customize the behavior of the @key{TAB}
(@code{indent-for-tab-command}) command. If the value is @code{t}
(the default), the command normally just indents the current line. If
the value is @code{nil}, the command indents the current line only if
point is at the left margin or in the line's indentation; otherwise,
it inserts a tab character. If the value is @code{complete}, the
command first tries to indent the current line, and if the line was
already indented, it calls @code{completion-at-point} to complete the
text at point (@pxref{Completion in Buffers}).
@end defopt
@node Region Indent
@subsection Indenting an Entire Region
......@@ -2827,7 +2851,7 @@ faster to process chunks of text that have the same property value.
comparing property values. In all cases, @var{object} defaults to the
current buffer.
For high performance, it's very important to use the @var{limit}
For good performance, it's very important to use the @var{limit}
argument to these functions, especially the ones that search for a
single property---otherwise, they may spend a long time scanning to the
end of the buffer, if the property you are interested in does not change.
......@@ -2839,15 +2863,15 @@ different properties.
@defun next-property-change pos &optional object limit
The function scans the text forward from position @var{pos} in the
string or buffer @var{object} till it finds a change in some text
string or buffer @var{object} until it finds a change in some text
property, then returns the position of the change. In other words, it
returns the position of the first character beyond @var{pos} whose
properties are not identical to those of the character just after
@var{pos}.
If @var{limit} is non-@code{nil}, then the scan ends at position
@var{limit}. If there is no property change before that point,
@code{next-property-change} returns @var{limit}.
@var{limit}. If there is no property change before that point, this
function returns @var{limit}.
The value is @code{nil} if the properties remain unchanged all the way
to the end of @var{object} and @var{limit} is @code{nil}. If the value
......@@ -2980,10 +3004,9 @@ character.
@item face
@cindex face codes of text
@kindex face @r{(text property)}
You can use the property @code{face} to control the font and color of
text. @xref{Faces}, for more information.
@code{face} can be the following:
The @code{face} property controls the appearance of the character,
such as its font and color. @xref{Faces}. The value of the property
can be the following:
@itemize @bullet
@item
......@@ -2996,10 +3019,10 @@ face attribute name and @var{value} is a meaningful value for that
attribute. With this feature, you do not need to create a face each
time you want to specify a particular attribute for certain text.
@xref{Face Attributes}.
@end itemize
@code{face} can also be a list, where each element uses one of the
forms listed above.
@item
A list, where each element uses one of the two forms listed above.
@end itemize
Font Lock mode (@pxref{Font Lock Mode}) works in most buffers by
dynamically updating the @code{face} property of characters based on
......@@ -3354,15 +3377,15 @@ of the text.
Self-inserting characters normally take on the same properties as the
preceding character. This is called @dfn{inheritance} of properties.
In a Lisp program, you can do insertion with inheritance or without,
depending on your choice of insertion primitive. The ordinary text
insertion functions such as @code{insert} do not inherit any properties.
They insert text with precisely the properties of the string being
inserted, and no others. This is correct for programs that copy text
from one context to another---for example, into or out of the kill ring.
To insert with inheritance, use the special primitives described in this
section. Self-inserting characters inherit properties because they work
using these primitives.
A Lisp program can do insertion with inheritance or without,
depending on the choice of insertion primitive. The ordinary text
insertion functions, such as @code{insert}, do not inherit any
properties. They insert text with precisely the properties of the
string being inserted, and no others. This is correct for programs
that copy text from one context to another---for example, into or out
of the kill ring. To insert with inheritance, use the special
primitives described in this section. Self-inserting characters
inherit properties because they work using these primitives.
When you do insertion with inheritance, @emph{which} properties are
inherited, and from where, depends on which properties are @dfn{sticky}.
......@@ -4063,46 +4086,64 @@ The decoding functions ignore newline characters in the encoded text.
@node Checksum/Hash
@section Checksum/Hash
@cindex MD5 checksum
@cindex hashing, secure
@cindex SHA-1
@cindex message digest computation
MD5 cryptographic checksums, or @dfn{message digests}, are 128-bit
``fingerprints'' of a document or program. They are used to verify
that you have an exact and unaltered copy of the data. The algorithm
to calculate the MD5 message digest is defined in Internet
RFC@footnote{
For an explanation of what is an RFC, see the footnote in @ref{Base
64}.
}1321. This section describes the Emacs facilities for computing
message digests and other forms of ``secure hash''.
@cindex SHA hash
@cindex hash, cryptographic
@cindex cryptographic hash
Emacs has built-in support for computing @dfn{cryptographic hashes}.
A cryptographic hash, or @dfn{checksum}, is a digital ``fingerprint''
of a piece of data (e.g.@: a block of text) which can be used to check
that you have an unaltered copy of that data.
@cindex message digest
Emacs supports several common cryptographic hash algorithms: MD5,
SHA-1, SHA-2, SHA-224, SHA-256, SHA-384 and SHA-512. MD5 is the
oldest of these algorithms, and is commonly used in @dfn{message
digests} to check the integrity of messages transmitted over a
network. MD5 is not ``collision resistant'' (i.e.@: it is possible to
deliberately design different pieces of data which have the same MD5
hash), so you should not used it for anything security-related. A
similar theoretical weakness also exists in SHA-1. Therefore, for
security-related applications you should use the other hash types,
such as SHA-2.
@defun md5 object &optional start end coding-system noerror
This function returns the MD5 message digest of @var{object}, which
should be a buffer or a string.
@defun secure-hash algorithm object &optional start end binary
This function returns a hash for @var{object}. The argument
@var{algorithm} is a symbol stating which hash to compute: one of
@code{md5}, @code{sha1}, @code{sha224}, @code{sha256}, @code{sha384}
or @code{sha512}. The argument @var{object} should be a buffer or a
string.
The two optional arguments @var{start} and @var{end} are character
The optional arguments @var{start} and @var{end} are character
positions specifying the portion of @var{object} to compute the
message digest for. If they are @code{nil} or omitted, the digest is
message digest for. If they are @code{nil} or omitted, the hash is
computed for the whole of @var{object}.
The function @code{md5} does not compute the message digest directly
from the internal Emacs representation of the text (@pxref{Text
Representations}). Instead, it encodes the text using a coding
system, and computes the message digest from the encoded text. The
optional fourth argument @var{coding-system} specifies which coding
system to use for encoding the text. It should be the same coding
system that you used to read the text, or that you used or will use
when saving or sending the text. @xref{Coding Systems}, for more
information about coding systems.
If @var{coding-system} is @code{nil} or omitted, the default depends
on @var{object}. If @var{object} is a buffer, the default for
@var{coding-system} is whatever coding system would be chosen by
default for writing this text into a file. If @var{object} is a
string, the user's most preferred coding system (@pxref{Recognize
Coding, prefer-coding-system, the description of
@code{prefer-coding-system}, emacs, GNU Emacs Manual}) is used.
If the argument @var{binary} is omitted or @code{nil}, the function
returns the @dfn{text form} of the hash, as an ordinary Lisp string.
If @var{binary} is non-@code{nil}, it returns the hash in @dfn{binary
form}, as a sequence of bytes stored in a unibyte string.
This function does not compute the hash directly from the internal
representation of @var{object}'s text (@pxref{Text Representations}).
Instead, it encodes the text using a coding system (@pxref{Coding
Systems}), and computes the hash from that encoded text. If
@var{object} is a buffer, the coding system used is the one which
would be chosen by default for writing the text into a file. If
@var{object} is a string, the user's preferred coding system is used
(@pxref{Recognize Coding,,, emacs, GNU Emacs Manual}).
@end defun
@defun md5 object &optional start end coding-system noerror
This function returns an MD5 hash. It is semi-obsolete, since for
most purposes it is equivalent to calling @code{secure-hash} with
@code{md5} as the @var{algorithm} argument. The @var{object},
@var{start} and @var{end} arguments have the same meanings as in
@code{secure-hash}.
If @var{coding-system} is non-@code{nil}, it specifies a coding system
to use to encode the text; if omitted or @code{nil}, the default
coding system is used, like in @code{secure-hash}.
Normally, @code{md5} signals an error if the text can't be encoded
using the specified or chosen coding system. However, if
......@@ -4110,65 +4151,53 @@ using the specified or chosen coding system. However, if
coding instead.
@end defun
@defun secure-hash algorithm object &optional start end binary
This function provides a general interface to a variety of secure
hashing algorithms. As well as the MD5 algorithm, it supports SHA-1,
SHA-2, SHA-224, SHA-256, SHA-384 and SHA-512. The argument
@var{algorithm} is a symbol stating which hash to compute. The
arguments @var{object}, @var{start}, and @var{end} are as for the
@code{md5} function. If the optional argument @var{binary} is
non-@code{nil}, returns a string in binary form.
@end defun
@node Parsing HTML
@section Parsing HTML
@node Parsing HTML/XML
@section Parsing HTML and XML
@cindex parsing html
When Emacs is compiled with libxml2 support, the following functions
are available to parse HTML or XML text into Lisp object trees.
@defun libxml-parse-html-region start end &optional base-url
This function provides HTML parsing via the @code{libxml2} library.
It parses ``real world'' HTML and tries to return a sensible parse tree
regardless.
This function parses the text between @var{start} and @var{end} as
HTML, and returns a list representing the HTML @dfn{parse tree}. It
attempts to handle ``real world'' HTML by robustly coping with syntax
mistakes.
In addition to @var{start} and @var{end} (specifying the start and end
of the region to act on), it takes an optional parameter,
@var{base-url}, which is used to expand relative URLs in the document,
if any.
The optional argument @var{base-url}, if non-@code{nil}, should be a
string specifying the base URL for relative URLs occurring in links.
Here's an example demonstrating the structure of the parsed data you
get out. Given this HTML document:
In the parse tree, each HTML node is represented by a list in which
the first element is a symbol representing the node name, the second
element is an alist of node attributes, and the remaining elements are
the subnodes.
The following example demonstrates this. Given this (malformed) HTML
document:
@example
<html><hEad></head><body width=101><div class=thing>Foo<div>Yes
<html><head></head><body width=101><div class=thing>Foo<div>Yes
@end example
You get this parse tree:
@noindent
A call to @code{libxml-parse-html-region} returns this:
@example
(html
(head)
(body
(:width . "101")
(div
(:class . "thing")
(text . "Foo")
(div
(text . "Yes\n")))))
(html ()
(head ())
(body ((width . "101"))
(div ((class . "thing"))
"Foo"
(div ()
"Yes"))))
@end example
It's a simple tree structure, where the @code{car} for each node is
the name of the node, and the @code{cdr} is the value, or the list of
values.
Attributes are coded the same way as child nodes, but with @samp{:} as
the first character.
@end defun
@cindex parsing xml
@defun libxml-parse-xml-region start end &optional base-url
This is much the same as @code{libxml-parse-html-region} above, but
operates on XML instead of HTML, and is correspondingly stricter about
syntax.
This function is the same as @code{libxml-parse-html-region}, except
that it parses the text as XML rather than HTML (so it is stricter
about syntax).
@end defun
@node Atomic Changes
......
......@@ -1076,7 +1076,8 @@ Text
* Registers:: How registers are implemented. Accessing
the text or position stored in a register.
* Base 64:: Conversion to or from base 64 encoding.
* Checksum/Hash:: Computing "message digests"/"checksums"/"hashes".
* Checksum/Hash:: Computing cryptographic hashes.
* Parsing HTML/XML:: Parsing HTML and XML.
* Atomic Changes:: Installing several buffer changes "atomically".
* Change Hooks:: Supplying functions to be run when text is changed.
......
......@@ -1075,7 +1075,8 @@ Text
* Registers:: How registers are implemented. Accessing
the text or position stored in a register.
* Base 64:: Conversion to or from base 64 encoding.
* Checksum/Hash:: Computing "message digests"/"checksums"/"hashes".
* Checksum/Hash:: Computing cryptographic hashes.
* Parsing HTML/XML:: Parsing HTML and XML.
* Atomic Changes:: Installing several buffer changes "atomically".
* Change Hooks:: Supplying functions to be run when text is changed.
......
......@@ -1482,13 +1482,12 @@ These require Emacs to be built with ImageMagick support.
image-transform-fit-to-height, image-transform-fit-to-width,
image-transform-set-rotation, image-transform-set-scale.
+++
** XML and HTML parsing
If Emacs is compiled with libxml2 support, there are two new functions:
`libxml-parse-html-region' (which parses "real world" HTML) and
`libxml-parse-xml-region' (which parses XML). Both return an Emacs
Lisp parse tree.
FIXME: These should be front-ended by xml.el.
If Emacs is compiled with libxml2 support, there are two new
functions: `libxml-parse-html-region' (which parses "real world" HTML)
and `libxml-parse-xml-region' (which parses XML). Both return an
Emacs Lisp parse tree.
** GnuTLS
......
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