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October 2001, --Jcid
Last update: Dec 2004
---------------
THE HTML PARSER
---------------
Dillo's parser is more than just a HTML parser, it does XHTML
and plain text also. It has parsing 'modes' that define its
behaviour while working:
typedef enum {
DILLO_HTML_PARSE_MODE_INIT,
DILLO_HTML_PARSE_MODE_STASH,
DILLO_HTML_PARSE_MODE_STASH_AND_BODY,
DILLO_HTML_PARSE_MODE_BODY,
DILLO_HTML_PARSE_MODE_VERBATIM,
DILLO_HTML_PARSE_MODE_PRE
} DilloHtmlParseMode;
The parser works upon a token-grained basis, i.e., the data
stream is parsed into tokens and the parser is fed with them. The
process is simple: whenever the cache has new data, it gets
passed to Html_write, which groups data into tokens and calls the
appropriate functions for the token type (TAG, SPACE or WORD).
Note: when in DILLO_HTML_PARSE_MODE_VERBATIM, the parser
doesn't try to split the data stream into tokens anymore, it
simply collects until the closing tag.
------
TOKENS
------
* A chunk of WHITE SPACE --> Html_process_space
* TAG --> Html_process_tag
The tag-start is defined by two adjacent characters:
first : '<'
second: ALPHA | '/' | '!' | '?'
Note: comments are discarded ( <!-- ... --> )
The tag's end is not as easy to find, nor to deal with!:
1) The HTML 4.01 sec. 3.2.2 states that "Attribute/value
pairs appear before the final '>' of an element's start tag",
but it doesn't define how to discriminate the "final" '>'.
2) '<' and '>' should be escaped as '<' and '>' inside
attribute values.
3) The XML SPEC for XHTML states:
AttrValue ::== '"' ([^<&"] | Reference)* '"' |
"'" ([^<&'] | Reference)* "'"
Current parser honors the XML SPEC.
As it's a common mistake for human authors to mistype or
forget one of the quote marks of an attribute value; the
parser solves the problem with a look-ahead technique
(otherwise the parser could skip significative amounts of
well written HTML).
* WORD --> Html_process_word
A word is anything that doesn't start with SPACE, and that's
outside of a tag, up to the first SPACE or tag start.
SPACE = ' ' | \n | \r | \t | \f | \v
-----------------
THE PARSING STACK
-----------------
The parsing state of the document is kept in a stack:
struct _DilloHtml {
[...]
DilloHtmlState *stack;
gint stack_top; /* Index to the top of the stack [0 based] */
gint stack_max;
[...]
};
struct _DilloHtmlState {
char *tag;
DwStyle *style, *table_cell_style;
DilloHtmlParseMode parse_mode;
DilloHtmlTableMode table_mode;
gint list_level;
gint list_number;
DwWidget *page, *table;
gint32 current_bg_color;
};
Basically, when a TAG is processed, a new state is pushed into
the 'stack' and its 'style' is set to reflect the desired
appearance (details in DwStyle.txt).
That way, when a word is processed later (added to the Dw), all
the information is within the top state.
Closing TAGs just pop the stack.
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