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(libhtmllib.tex): Revised documentation for HTML support.

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@ -5,19 +5,23 @@
\renewcommand{\indexsubitem}{(in module htmllib)}
This module defines a number of classes which can serve as a basis for
parsing text files formatted in HTML (HyperText Mark-up Language).
The classes are not directly concerned with I/O --- the have to be fed
their input in string form, and will make calls to methods of a
``formatter'' object in order to produce output. The classes are
designed to be used as base classes for other classes in order to add
functionality, and allow most of their methods to be extended or
overridden. In turn, the classes are derived from and extend the
class \code{SGMLParser} defined in module \code{sgmllib}.
This module defines a class which can serve as a base for parsing text
files formatted in the HyperText Mark-up Language (HTML). The class
is not directly concerned with I/O --- it must be provided with input
in string form via a method, and makes calls to methods of a
``formatter'' object in order to produce output. The
\code{HTMLParser} class is designed to be used as a base class for
other classes in order to add functionality, and allows most of its
methods to be extended or overridden. In turn, this class is derived
from and extends the \code{SGMLParser} class defined in module
\code{sgmllib}. Two implementations of formatter objects are
provided in the \code{formatter} module; refer to the documentation
for that module for information on the formatter interface.
\index{SGML}
\stmodindex{sgmllib}
\ttindex{SGMLParser}
\index{formatter}
\stmodindex{formatter}
The following is a summary of the interface defined by
\code{sgmllib.SGMLParser}:
@ -27,15 +31,17 @@ The following is a summary of the interface defined by
\item
The interface to feed data to an instance is through the \code{feed()}
method, which takes a string argument. This can be called with as
little or as much text at a time as desired;
\code{p.feed(a); p.feed(b)} has the same effect as \code{p.feed(a+b)}.
When the data contains complete
HTML elements, these are processed immediately; incomplete elements
are saved in a buffer. To force processing of all unprocessed data,
call the \code{close()} method.
little or as much text at a time as desired; \code{p.feed(a);
p.feed(b)} has the same effect as \code{p.feed(a+b)}. When the data
contains complete HTML tags, these are processed immediately;
incomplete elements are saved in a buffer. To force processing of all
unprocessed data, call the \code{close()} method.
Example: to parse the entire contents of a file, do\\
\code{parser.feed(open(file).read()); parser.close()}.
For example, to parse the entire contents of a file, use:
\begin{verbatim}
parser.feed(open('myfile.html').read())
parser.close()
\end{verbatim}
\item
The interface to define semantics for HTML tags is very simple: derive
@ -52,223 +58,60 @@ should define the \code{do_\var{tag}} method.
\end{itemize}
The module defines the following classes:
The module defines a single class:
\begin{funcdesc}{HTMLParser}{}
This is the most basic HTML parser class. It defines one additional
entity name over the names defined by the \code{SGMLParser} base
class, \code{\•}. It also defines handlers for the following
tags: \code{<LISTING>...</LISTING>}, \code{<XMP>...</XMP>}, and
\code{<PLAINTEXT>} (the latter is terminated only by end of file).
\begin{funcdesc}{HTMLParser}{formatter}
This is the basic HTML parser class. It supports all entity names
required by the HTML 2.0 specification (RFC 1866). It also defines
handlers for all HTML 2.0 and many HTML 3.0 and 3.2 elements.
\end{funcdesc}
\begin{funcdesc}{CollectingParser}{}
This class, derived from \code{HTMLParser}, collects various useful
bits of information from the HTML text. To this end it defines
additional handlers for the following tags: \code{<A>...</A>},
\code{<HEAD>...</HEAD>}, \code{<BODY>...</BODY>},
\code{<TITLE>...</TITLE>}, \code{<NEXTID>}, and \code{<ISINDEX>}.
In addition to tag methods, the \code{HTMLParser} class provides some
additional methods and instance variables for use within tag methods.
\begin{datadesc}{formatter}
This is the formatter instance associated with the parser.
\end{datadesc}
\begin{datadesc}{nofill}
Boolean flag which should be true when whitespace should not be
collapsed, or false when it should be. In general, this should only
be true when character data is to be treated as ``preformatted'' text,
as within a \code{<PRE>} element. The default value is false. This
affects the operation of \code{handle_data()} and \code{save_end()}.
\end{datadesc}
\begin{funcdesc}{anchor_bgn}{href\, name\, type}
This method is called at the start of an anchor region. The arguments
correspond to the attributes of the \code{<A>} tag with the same
names. The default implementation maintains a list of hyperlinks
(defined by the \code{href} argument) within the document. The list
of hyperlinks is available as the data attribute \code{anchorlist}.
\end{funcdesc}
\begin{funcdesc}{FormattingParser}{formatter\, stylesheet}
This class, derived from \code{CollectingParser}, interprets a wide
selection of HTML tags so it can produce formatted output from the
parsed data. It is initialized with two objects, a \var{formatter}
which should define a number of methods to format text into
paragraphs, and a \var{stylesheet} which defines a number of static
parameters for the formatting process. Formatters and style sheets
are documented later in this section.
\index{formatter}
\index{style sheet}
\begin{funcdesc}{anchor_end}{}
This method is called at the end of an anchor region. The default
implementation adds a textual footnote marker using an index into the
list of hyperlinks created by \code{anchor_bgn()}.
\end{funcdesc}
\begin{funcdesc}{AnchoringParser}{formatter\, stylesheet}
This class, derived from \code{FormattingParser}, extends the handling
of the \code{<A>...</A>} tag pair to call the formatter's
\code{bgn_anchor()} and \code{end_anchor()} methods. This allows the
formatter to display the anchor in a different font or color, etc.
\begin{funcdesc}{handle_image}{source\, alt\optional{\, ismap\optional{\, align\optional{\, width\optional{\, height}}}}}
This method is called to handle images. The default implementation
simply passes the \code{alt} value to the \code{handle_data()}
method.
\end{funcdesc}
Instances of \code{CollectingParser} (and thus also instances of
\code{FormattingParser} and \code{AnchoringParser}) have the following
instance variables:
\begin{datadesc}{anchornames}
A list of the values of the \code{NAME} attributes of the \code{<A>}
tags encountered.
\end{datadesc}
\begin{datadesc}{anchors}
A list of the values of \code{HREF} attributes of the \code{<A>} tags
encountered.
\end{datadesc}
\begin{datadesc}{anchortypes}
A list of the values of the \code{TYPE} attributes of the \code{<A>}
tags encountered.
\end{datadesc}
\begin{datadesc}{inanchor}
Outside an \code{<A>...</A>} tag pair, this is zero. Inside such a
pair, it is a unique integer, which is positive if the anchor has a
\code{HREF} attribute, negative if it hasn't. Its absolute value is
one more than the index of the anchor in the \code{anchors},
\code{anchornames} and \code{anchortypes} lists.
\end{datadesc}
\begin{datadesc}{isindex}
True if the \code{<ISINDEX>} tag has been encountered.
\end{datadesc}
\begin{datadesc}{nextid}
The attribute list of the last \code{<NEXTID>} tag encountered, or
an empty list if none.
\end{datadesc}
\begin{datadesc}{title}
The text inside the last \code{<TITLE>...</TITLE>} tag pair, or
\code{''} if no title has been encountered yet.
\end{datadesc}
The \code{anchors}, \code{anchornames} and \code{anchortypes} lists
are ``parallel arrays'': items in these lists with the same index
pertain to the same anchor. Missing attributes default to the empty
string. Anchors with neither a \code{HREF} nor a \code{NAME}
attribute are not entered in these lists at all.
The module also defines a number of style sheet classes. These should
never be instantiated --- their class variables are the only behavior
required. Note that style sheets are specifically designed for a
particular formatter implementation. The currently defined style
sheets are:
\index{style sheet}
\begin{datadesc}{NullStylesheet}
A style sheet for use on a dumb output device such as an \ASCII{}
terminal.
\end{datadesc}
\begin{datadesc}{X11Stylesheet}
A style sheet for use with an X11 server.
\end{datadesc}
\begin{datadesc}{MacStylesheet}
A style sheet for use on Apple Macintosh computers.
\end{datadesc}
\begin{datadesc}{StdwinStylesheet}
A style sheet for use with the \code{stdwin} module; it is an alias
for either \code{X11Stylesheet} or \code{MacStylesheet}.
\bimodindex{stdwin}
\end{datadesc}
\begin{datadesc}{GLStylesheet}
A style sheet for use with the SGI Graphics Library and its font
manager (the SGI-specific built-in modules \code{gl} and \code{fm}).
\bimodindex{gl}
\bimodindex{fm}
\end{datadesc}
Style sheets have the following class variables:
\begin{datadesc}{stdfontset}
A list of up to four font definititions, respectively for the roman,
italic, bold and constant-width variant of a font for normal text. If
the list contains less than four font definitions, the last item is
used as the default for missing items. The type of a font definition
depends on the formatter in use; its only use is as a parameter to the
formatter's \code{setfont()} method.
\end{datadesc}
\begin{datadesc}{h1fontset}
\dataline{h2fontset}
\dataline{h3fontset}
The font set used for various headers (text inside \code{<H1>...</H1>}
tag pairs etc.).
\end{datadesc}
\begin{datadesc}{stdindent}
The indentation of normal text. This is measured in the ``native''
units of the formatter in use; for some formatters these are
characters, for others (especially those that actually support
variable-spacing fonts) in pixels or printer points.
\end{datadesc}
\begin{datadesc}{ddindent}
The indentation used for the first level of \code{<DD>} tags.
\end{datadesc}
\begin{datadesc}{ulindent}
The indentation used for the first level of \code{<UL>} tags.
\end{datadesc}
\begin{datadesc}{h1indent}
The indentation used for level 1 headers.
\end{datadesc}
\begin{datadesc}{h2indent}
The indentation used for level 2 headers.
\end{datadesc}
\begin{datadesc}{literalindent}
The indentation used for literal text (text inside
\code{<PRE>...</PRE>} and similar tag pairs).
\end{datadesc}
Although no documented implementation of a formatter exists, the
\code{FormattingParser} class assumes that formatters have a
certain interface. This interface requires the following methods:
\index{formatter}
\begin{funcdesc}{setfont}{fontspec}
Set the font to be used subsequently. The \var{fontspec} argument is
an item in a style sheet's font set.
\begin{funcdesc}{save_bgn}{}
Begins saving character data in a buffer instead of sending it to the
formatter object. Retrieve the stored data via \code{save_end()}
Use of the \code{save_bgn()} / \code{save_end()} pair may not be
nested.
\end{funcdesc}
\begin{funcdesc}{flush}{}
Finish the current line, if not empty, and begin a new one.
\begin{funcdesc}{save_end}{}
Ends buffering character data and returns all data saved since the
preceeding call to \code{save_bgn()}. If \code{nofill} flag is false,
whitespace is collapsed to single spaces. A call to this method
without a preceeding call to \code{save_bgn()} will raise a
\code{TypeError} exception.
\end{funcdesc}
\begin{funcdesc}{setleftindent}{n}
Set the left indentation of the following lines to \var{n} units.
\end{funcdesc}
\begin{funcdesc}{needvspace}{n}
Require at least \var{n} blank lines before the next line. Implies
\code{flush()}.
\end{funcdesc}
\begin{funcdesc}{addword}{word\, space}
Add a \var{word} to the current paragraph, followed by \var{space}
spaces.
\end{funcdesc}
\begin{datadesc}{nospace}
If this instance variable is true, empty words should be ignored by
\code{addword}. It should be set to false after a non-empty word has
been added.
\end{datadesc}
\begin{funcdesc}{setjust}{justification}
Set the justification of the current paragraph. The
\var{justification} can be \code{'c'} (center), \code{'l'} (left
justified), \code{'r'} (right justified) or \code{'lr'} (left and
right justified).
\end{funcdesc}
\begin{funcdesc}{bgn_anchor}{id}
Begin an anchor. The \var{id} parameter is the value of the parser's
\code{inanchor} attribute.
\end{funcdesc}
\begin{funcdesc}{end_anchor}{id}
End an anchor. The \var{id} parameter is the value of the parser's
\code{inanchor} attribute.
\end{funcdesc}
A sample formatter implementation can be found in the module
\code{fmt}, which in turn uses the module \code{Para}. These modules are
not intended as standard library modules; they are available as an
example of how to write a formatter.
\ttindex{fmt}
\ttindex{Para}

293
Doc/libhtmllib.tex
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@ -5,19 +5,23 @@
\renewcommand{\indexsubitem}{(in module htmllib)}
This module defines a number of classes which can serve as a basis for
parsing text files formatted in HTML (HyperText Mark-up Language).
The classes are not directly concerned with I/O --- the have to be fed
their input in string form, and will make calls to methods of a
``formatter'' object in order to produce output. The classes are
designed to be used as base classes for other classes in order to add
functionality, and allow most of their methods to be extended or
overridden. In turn, the classes are derived from and extend the
class \code{SGMLParser} defined in module \code{sgmllib}.
This module defines a class which can serve as a base for parsing text
files formatted in the HyperText Mark-up Language (HTML). The class
is not directly concerned with I/O --- it must be provided with input
in string form via a method, and makes calls to methods of a
``formatter'' object in order to produce output. The
\code{HTMLParser} class is designed to be used as a base class for
other classes in order to add functionality, and allows most of its
methods to be extended or overridden. In turn, this class is derived
from and extends the \code{SGMLParser} class defined in module
\code{sgmllib}. Two implementations of formatter objects are
provided in the \code{formatter} module; refer to the documentation
for that module for information on the formatter interface.
\index{SGML}
\stmodindex{sgmllib}
\ttindex{SGMLParser}
\index{formatter}
\stmodindex{formatter}
The following is a summary of the interface defined by
\code{sgmllib.SGMLParser}:
@ -27,15 +31,17 @@ The following is a summary of the interface defined by
\item
The interface to feed data to an instance is through the \code{feed()}
method, which takes a string argument. This can be called with as
little or as much text at a time as desired;
\code{p.feed(a); p.feed(b)} has the same effect as \code{p.feed(a+b)}.
When the data contains complete
HTML elements, these are processed immediately; incomplete elements
are saved in a buffer. To force processing of all unprocessed data,
call the \code{close()} method.
little or as much text at a time as desired; \code{p.feed(a);
p.feed(b)} has the same effect as \code{p.feed(a+b)}. When the data
contains complete HTML tags, these are processed immediately;
incomplete elements are saved in a buffer. To force processing of all
unprocessed data, call the \code{close()} method.
Example: to parse the entire contents of a file, do\\
\code{parser.feed(open(file).read()); parser.close()}.
For example, to parse the entire contents of a file, use:
\begin{verbatim}
parser.feed(open('myfile.html').read())
parser.close()
\end{verbatim}
\item
The interface to define semantics for HTML tags is very simple: derive
@ -52,223 +58,60 @@ should define the \code{do_\var{tag}} method.
\end{itemize}
The module defines the following classes:
The module defines a single class:
\begin{funcdesc}{HTMLParser}{}
This is the most basic HTML parser class. It defines one additional
entity name over the names defined by the \code{SGMLParser} base
class, \code{\&bullet;}. It also defines handlers for the following
tags: \code{<LISTING>...</LISTING>}, \code{<XMP>...</XMP>}, and
\code{<PLAINTEXT>} (the latter is terminated only by end of file).
\begin{funcdesc}{HTMLParser}{formatter}
This is the basic HTML parser class. It supports all entity names
required by the HTML 2.0 specification (RFC 1866). It also defines
handlers for all HTML 2.0 and many HTML 3.0 and 3.2 elements.
\end{funcdesc}
\begin{funcdesc}{CollectingParser}{}
This class, derived from \code{HTMLParser}, collects various useful
bits of information from the HTML text. To this end it defines
additional handlers for the following tags: \code{<A>...</A>},
\code{<HEAD>...</HEAD>}, \code{<BODY>...</BODY>},
\code{<TITLE>...</TITLE>}, \code{<NEXTID>}, and \code{<ISINDEX>}.
In addition to tag methods, the \code{HTMLParser} class provides some
additional methods and instance variables for use within tag methods.
\begin{datadesc}{formatter}
This is the formatter instance associated with the parser.
\end{datadesc}
\begin{datadesc}{nofill}
Boolean flag which should be true when whitespace should not be
collapsed, or false when it should be. In general, this should only
be true when character data is to be treated as ``preformatted'' text,
as within a \code{<PRE>} element. The default value is false. This
affects the operation of \code{handle_data()} and \code{save_end()}.
\end{datadesc}
\begin{funcdesc}{anchor_bgn}{href\, name\, type}
This method is called at the start of an anchor region. The arguments
correspond to the attributes of the \code{<A>} tag with the same
names. The default implementation maintains a list of hyperlinks
(defined by the \code{href} argument) within the document. The list
of hyperlinks is available as the data attribute \code{anchorlist}.
\end{funcdesc}
\begin{funcdesc}{FormattingParser}{formatter\, stylesheet}
This class, derived from \code{CollectingParser}, interprets a wide
selection of HTML tags so it can produce formatted output from the
parsed data. It is initialized with two objects, a \var{formatter}
which should define a number of methods to format text into
paragraphs, and a \var{stylesheet} which defines a number of static
parameters for the formatting process. Formatters and style sheets
are documented later in this section.
\index{formatter}
\index{style sheet}
\begin{funcdesc}{anchor_end}{}
This method is called at the end of an anchor region. The default
implementation adds a textual footnote marker using an index into the
list of hyperlinks created by \code{anchor_bgn()}.
\end{funcdesc}
\begin{funcdesc}{AnchoringParser}{formatter\, stylesheet}
This class, derived from \code{FormattingParser}, extends the handling
of the \code{<A>...</A>} tag pair to call the formatter's
\code{bgn_anchor()} and \code{end_anchor()} methods. This allows the
formatter to display the anchor in a different font or color, etc.
\begin{funcdesc}{handle_image}{source\, alt\optional{\, ismap\optional{\, align\optional{\, width\optional{\, height}}}}}
This method is called to handle images. The default implementation
simply passes the \code{alt} value to the \code{handle_data()}
method.
\end{funcdesc}
Instances of \code{CollectingParser} (and thus also instances of
\code{FormattingParser} and \code{AnchoringParser}) have the following
instance variables:
\begin{datadesc}{anchornames}
A list of the values of the \code{NAME} attributes of the \code{<A>}
tags encountered.
\end{datadesc}
\begin{datadesc}{anchors}
A list of the values of \code{HREF} attributes of the \code{<A>} tags
encountered.
\end{datadesc}
\begin{datadesc}{anchortypes}
A list of the values of the \code{TYPE} attributes of the \code{<A>}
tags encountered.
\end{datadesc}
\begin{datadesc}{inanchor}
Outside an \code{<A>...</A>} tag pair, this is zero. Inside such a
pair, it is a unique integer, which is positive if the anchor has a
\code{HREF} attribute, negative if it hasn't. Its absolute value is
one more than the index of the anchor in the \code{anchors},
\code{anchornames} and \code{anchortypes} lists.
\end{datadesc}
\begin{datadesc}{isindex}
True if the \code{<ISINDEX>} tag has been encountered.
\end{datadesc}
\begin{datadesc}{nextid}
The attribute list of the last \code{<NEXTID>} tag encountered, or
an empty list if none.
\end{datadesc}
\begin{datadesc}{title}
The text inside the last \code{<TITLE>...</TITLE>} tag pair, or
\code{''} if no title has been encountered yet.
\end{datadesc}
The \code{anchors}, \code{anchornames} and \code{anchortypes} lists
are ``parallel arrays'': items in these lists with the same index
pertain to the same anchor. Missing attributes default to the empty
string. Anchors with neither a \code{HREF} nor a \code{NAME}
attribute are not entered in these lists at all.
The module also defines a number of style sheet classes. These should
never be instantiated --- their class variables are the only behavior
required. Note that style sheets are specifically designed for a
particular formatter implementation. The currently defined style
sheets are:
\index{style sheet}
\begin{datadesc}{NullStylesheet}
A style sheet for use on a dumb output device such as an \ASCII{}
terminal.
\end{datadesc}
\begin{datadesc}{X11Stylesheet}
A style sheet for use with an X11 server.
\end{datadesc}
\begin{datadesc}{MacStylesheet}
A style sheet for use on Apple Macintosh computers.
\end{datadesc}
\begin{datadesc}{StdwinStylesheet}
A style sheet for use with the \code{stdwin} module; it is an alias
for either \code{X11Stylesheet} or \code{MacStylesheet}.
\bimodindex{stdwin}
\end{datadesc}
\begin{datadesc}{GLStylesheet}
A style sheet for use with the SGI Graphics Library and its font
manager (the SGI-specific built-in modules \code{gl} and \code{fm}).
\bimodindex{gl}
\bimodindex{fm}
\end{datadesc}
Style sheets have the following class variables:
\begin{datadesc}{stdfontset}
A list of up to four font definititions, respectively for the roman,
italic, bold and constant-width variant of a font for normal text. If
the list contains less than four font definitions, the last item is
used as the default for missing items. The type of a font definition
depends on the formatter in use; its only use is as a parameter to the
formatter's \code{setfont()} method.
\end{datadesc}
\begin{datadesc}{h1fontset}
\dataline{h2fontset}
\dataline{h3fontset}
The font set used for various headers (text inside \code{<H1>...</H1>}
tag pairs etc.).
\end{datadesc}
\begin{datadesc}{stdindent}
The indentation of normal text. This is measured in the ``native''
units of the formatter in use; for some formatters these are
characters, for others (especially those that actually support
variable-spacing fonts) in pixels or printer points.
\end{datadesc}
\begin{datadesc}{ddindent}
The indentation used for the first level of \code{<DD>} tags.
\end{datadesc}
\begin{datadesc}{ulindent}
The indentation used for the first level of \code{<UL>} tags.
\end{datadesc}
\begin{datadesc}{h1indent}
The indentation used for level 1 headers.
\end{datadesc}
\begin{datadesc}{h2indent}
The indentation used for level 2 headers.
\end{datadesc}
\begin{datadesc}{literalindent}
The indentation used for literal text (text inside
\code{<PRE>...</PRE>} and similar tag pairs).
\end{datadesc}
Although no documented implementation of a formatter exists, the
\code{FormattingParser} class assumes that formatters have a
certain interface. This interface requires the following methods:
\index{formatter}
\begin{funcdesc}{setfont}{fontspec}
Set the font to be used subsequently. The \var{fontspec} argument is
an item in a style sheet's font set.
\begin{funcdesc}{save_bgn}{}
Begins saving character data in a buffer instead of sending it to the
formatter object. Retrieve the stored data via \code{save_end()}
Use of the \code{save_bgn()} / \code{save_end()} pair may not be
nested.
\end{funcdesc}
\begin{funcdesc}{flush}{}
Finish the current line, if not empty, and begin a new one.
\begin{funcdesc}{save_end}{}
Ends buffering character data and returns all data saved since the
preceeding call to \code{save_bgn()}. If \code{nofill} flag is false,
whitespace is collapsed to single spaces. A call to this method
without a preceeding call to \code{save_bgn()} will raise a
\code{TypeError} exception.
\end{funcdesc}
\begin{funcdesc}{setleftindent}{n}
Set the left indentation of the following lines to \var{n} units.
\end{funcdesc}
\begin{funcdesc}{needvspace}{n}
Require at least \var{n} blank lines before the next line. Implies
\code{flush()}.
\end{funcdesc}
\begin{funcdesc}{addword}{word\, space}
Add a \var{word} to the current paragraph, followed by \var{space}
spaces.
\end{funcdesc}
\begin{datadesc}{nospace}
If this instance variable is true, empty words should be ignored by
\code{addword}. It should be set to false after a non-empty word has
been added.
\end{datadesc}
\begin{funcdesc}{setjust}{justification}
Set the justification of the current paragraph. The
\var{justification} can be \code{'c'} (center), \code{'l'} (left
justified), \code{'r'} (right justified) or \code{'lr'} (left and
right justified).
\end{funcdesc}
\begin{funcdesc}{bgn_anchor}{id}
Begin an anchor. The \var{id} parameter is the value of the parser's
\code{inanchor} attribute.
\end{funcdesc}
\begin{funcdesc}{end_anchor}{id}
End an anchor. The \var{id} parameter is the value of the parser's
\code{inanchor} attribute.
\end{funcdesc}
A sample formatter implementation can be found in the module
\code{fmt}, which in turn uses the module \code{Para}. These modules are
not intended as standard library modules; they are available as an
example of how to write a formatter.
\ttindex{fmt}
\ttindex{Para}