The Tor Browser: layout/doc/obsolete/nav4-html.html@97036ab72558 (annotated)

layout/doc/obsolete/nav4-html.html@97036ab72558 (annotated)

layout/doc/obsolete/nav4-html.html

Tue, 06 Jan 2015 21:39:09 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Tue, 06 Jan 2015 21:39:09 +0100
branch: TOR_BUG_9701
changeset 8: 97036ab72558
permissions: -rw-r--r--

Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

 <!-- This Source Code Form is subject to the terms of the Mozilla Public
    - License, v. 2.0. If a copy of the MPL was not distributed with this
    - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
 <HTML>
 <HEAD>
    <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
    <META NAME="Author" CONTENT="Kipp E.B. HIckman">
    <META NAME="GENERATOR" CONTENT="Mozilla/4.03 [en] (WinNT; I) [Netscape]">
    <TITLE>HTML</TITLE>
    <BASE HREF="file:///s|/ns/xena/htmlpars/testhtml/">
 </HEAD>
 <BODY TEXT="#000000" BGCOLOR="#FFFFFF" LINK="#FF0000" VLINK="#800080" ALINK="#0000FF">
 <H2>
 HTML</H2>
 This documents describes the complete handling of HTML in magellan. The
 document covers the parsing process - how HTML is lexically analysized
 and then interprted. After the parsing process is discussed we give a detailed
 analysis of each HTML tag and the attributes that are supported, the values
 for the attributes and how the tag is treated by magellan.
 <H2>
 Parsing</H2>
 HTML is tokenized by an HTML scanner. The scanner is fed unicode data to
 parse. Stream converters are used to translate from various encodings to
 unicode. The scanner separates the input stream into tokens which consist
 of:
 <UL>
 <LI>
 text</LI>
 <LI>
 tags</LI>
 <LI>
 entities</LI>
 <LI>
 script-entities</LI>
 <LI>
 comments</LI>
 <LI>
 conditional comments</LI>
 </UL>
 The HTML parsing engine uses the HTML scanner for lexical anlaysis. The
 parsing engine operates by attacking the input stream in a set of well
 defined steps:
 <UL>
 <LI>
 The parser processes the head portion of the document first, without emitting
 any output. This is done to discover a few special features of html:</LI>
 <UL>
 <LI>
 The parser processes META tags looking for META TARGET</LI>
 <LI>
 The parser processes META tags looking for META tags which affect the character
 set. Nav4 handles the very first character set defining meta tag (all others
 are ignored) by reloading the document with the proper character conversion
 module inserted into the stream pipeline.</LI>
 </UL>
 <LI>
 After the head portion is processed the parser then proceeds to process
 the body of the document</LI>
 </UL>
 <H3>
 Tag Processing</H3>
 Tags are processed by the parser by locating a <B>"tag handler"</B> for
 the tag. The HTML parser serves as the tag handler for all of the builtin
 tags documented below. Tag attribute handling is done during translation
 of tags into content. This mapping translates the tag attributes into content
 data and into style data. The translation to style data is documented below
 by indicating the mapping from tag attributes to their CSS1 (plus extensions)
 equivalents.
 <H3>
 Special Hacks</H3>
 The following list describes hacks added to the magellan parsing engine
 to deal with navigator compatibility. These are just the parser hacks,
 not the layout or presentation hacks. Most hacks are intriduced for HTML
 syntax error recovering. HTML doesn't specify much how to handle those
 error conditions. Netscape has made big effort to render pages with non-prefect
 HTML. For many reasons, new browsers need to keep compatible in thsi area.
 <UL>
 <LI>
 Entities can be used as escape in quoted string. For value string in name-value
 pair,&nbsp; see <A HREF="../testhtml/quote001.html">compatibility test
 quote001.html</A>. Test line 70 shows that an entity quote at the begining
 means the value is NOT quoted. Test line 90 shows that if the value is
 started with a quote, then an entity quote does NOT terminate the value
 string.</LI>
 <LI>
 Wrapping tags are special tags such as title, textarea, server, script,
 style, and etc.. The comment in ns\lib\libparse\pa_parse.c says:</LI>
 <BR>&nbsp; /*
 <BR>&nbsp;&nbsp; * These tags are special in that, after opening one of
 them, all other tags are ignored until the matching
 <BR>&nbsp;&nbsp; * closing tag.
 <BR>&nbsp;&nbsp; */
 <BR>During the searching of an end tag, comments and quoted strings are
 observed. see <A HREF="../testhtml/title01.html">compatibility test title01.html</A>.
 .0 handles comments now, need to add quoted string.
 <LI>
 If a &lt;tr> or &lt;td> tag is seen outside any &lt;table> scope, it is
 ignored. see <A HREF="../testhtml/table110.htm">compatibility test table110.htm</A>.</LI>
 <LI>
 <FONT COLOR="#000000">In case of table in table but not in cell, table
 tags before the last table tag are ignored. We found this problem in some
 Netscape public pages, see bug #85118. For example, &lt;table> &lt;table
 border> .....,or &lt;table> &lt;tr> &lt;table border>...,&nbsp; the table
 will be displayed with border.&nbsp;</FONT> <A HREF="../testhtml/table201.html">compatibility
 test table201.html</A>. There table and tr tags are buffered for this recovery.
 When a TD or CAPTION tag is open, the buffer is flushed out, because we
 cannot buffer contents of TD or CAPTION for performance and memory constrains.
 They are subdoc's and can be very big. If we see a &lt;table> outside cell
 after previous table is flushed out, the new &lt;table> tag is ignored.
 Nav4.0 can discard previous table in such case. <A HREF="../testhtml/tableall.html">tableall.html
 </A>is the index for table test cases.</LI>
 <LI>
 Caption is not a commonly used feature. In Nav4.0, captions can be anywhere.
 For Captions outside cells, the first one takes effect. For captions inside
 cells, the last one takes effect, and they also close TD and TR. In 6.0,
 caption is limited to the standard position: after &lt;table>. Captions
 in other places are ignored, their contents are treated as text. See test
 case table05a.html to table05o.html.</LI>
 <LI>
 <FONT COLOR="#000000">For &lt;table> &lt;tr> &lt;tr>, the first &lt;tr>
 takes effect.</FONT></LI>
 <LI>
 The nav4 parser notices when it hits EOF and it's in the middle of scanning
 in a comment. When this happens, the parser goes back and looks for an
 improperly closed comment (e.g. a simple > instead of a -->). If it finds
 one, it reparses the input after closing out the comment.</LI>
 <LI>
 <FONT COLOR="#FF0000">XXX Brendan also pointed out that there is something
 similar done for tags, but I don't recall what it is right now.</FONT></LI>
 <LI>
 <FONT COLOR="#000000">When Nav4.0 sees the '&lt;' sign, it searchs for
 '>', observing quoted values. If it cannot find one till EOF, the '&lt;'
 sign is treated as text. In Xena 6.0, a limit is set for how far the '>'
 is searched. the default limit is 4096 char, and there is a API HTMLScanner.setMaxTagLength()
 to changed it. setting -1 means no limit, which is same as Nav4.0.</FONT></LI>
 </UL>
 <FONT COLOR="#FF0000">TODO:</FONT>
 <UL><FONT COLOR="#FF0000">Document the mapping of tag attributes into CSS1
 style, including any new "css1" attributes</FONT>
 <BR>&nbsp;</UL>
 <B>List of 6.0 features incompatible with 4.0</B>
 <UL>
 <LI>
 Navigator 4.0 value string is truncated at 82 characters. XENA60 limit
 is MAX_STRING_LENGTH = 2000.</LI>
 <BR>&nbsp;</UL>
 <HR WIDTH="100%">
 <H2>
 Tags (Categorically sorted)</H2>
 All line breaks are conditional. If the x coordinate is at the current
 left margin then a soft line break does nothing. Hard line breaks are ignored
 if the last tag did a hard line break.
 <P><B>divalign</B> = left | right | center | justify
 <BR><B>alignparam</B> = abscenter | left | right | texttop | absbottom
 | baseline | center | bottom | top | middle | absmiddle
 <BR><B>colorspec</B> = named-color | #xyz | #xxyyzz | #xxxyyyzzz | #xxxxyyyyzzzz
 <BR><B>clip</B> = [auto | value-or-pct-xy](1..4) (pct of width for even
 coordinates; pct of height for odd coordinates)
 <BR><B>value-or-pct = </B>an integer with an optional %; ifthe percent
 is present any following characters are ignored!
 <BR><B>coord-list</B> = <FONT COLOR="#DD0000">XXX</FONT>
 <BR><FONT COLOR="#000000"><B>whitespace-strip</B> = remove leading and
 trailing and any embedded whitespace that is not an actual space (e.g.
 newlines)</FONT>
 <H1>
 Head objects:</H1>
 <B>TITLE</B>
 <UL>The TITLE tag is a container tag whose contents are not HTML. The contents
 are pure text and are processed by the parser until the closing tag is
 found. There are no attributes on the tag and any whitespace present in
 the tag is compressed down with leading and trailing whitespace eliminated.
 The first TITLE tag found by the parser is used as the document's title
 (subsequent tags are ignored).</UL>
 <B>BASE</B>
 <UL>Sets the base element in the head portion of the document. Defines
 the base URL for <FONT COLOR="#DD0000">all</FONT>? links in the document.
 <BR>Attributes:
 <UL><B>HREF</B>=url [This is an absolute URL]
 <BR><B>TARGET</B>=string [must start with XP_ALPHA|XP_DIGIT|underscore
 otherwise nav4 ignores it]</UL>
 </UL>
 <B>META</B>
 <UL>Can define several header fields (content-encoding, author, etc.)
 <BR>Attributes:
 <UL><B>REL</B>=SMALL_BOOKMARK_ICON|LARGE_BOOKMARK_ICON
 <UL><B>SRC</B>=string</UL>
 <B>HTTP-EQUIV</B>="header: value"
 <UL><B>CONTENT</B>=string</UL>
 </UL>
 HTTP-EQUIV values (from libnet/mkutils.c NET_ParseMimeHeader):
 <UL>ACCEPT-RANGES
 <BR>CONTENT-DISPOSITION
 <BR>CONTENT-ENCODING
 <BR>CONTENT-RANGE
 <BR>CONTENT-TYPE [ defines character set only ]
 <BR>CONNECTION
 <BR>DATE
 <BR>EXPIRES
 <BR>EXT-CACHE
 <BR>LOCATION
 <BR>LAST-MODIFIED
 <BR>LINK
 <BR>PROXY-AUTHENTICATE
 <BR>PROXY-CONNECTION
 <BR>PRAGMA
 <BR>RANGE
 <BR>REFRESH
 <BR>SET-COOKIE
 <BR>SERVER
 <BR>WWW-AUTHENTICATE
 <BR>WWW-PROTECTION-TEMPLATE
 <BR>WINDOW-TARGET</UL>
 Style sheets and HTML w3c spec adds this:
 <UL>CONTENT-STYLE-TYPE [ last one wins; overrides header from server if
 any ]</UL>
 </UL>
 <B>LINK</B>
 <UL>List related resources. Used by extensions mechanism to find tag handlers.
 <FONT COLOR="#0000FF">/LINK == LINK!</FONT>
 <BR>Attributes:
 <UL><B>REL</B>=FONTDEF
 <UL><B>SRC</B>=url</UL>
 <B>REL</B>=STYLESHEET [ If MEDIA param is defined it must ==nc screen ]
 <UL><B>LANGUAGE</B>=LiveScript|Mocha|JavaScript1.1|JavaScript1.2
 <BR><B>TYPE</B>="text/javascript" | "text/css"
 <BR><B>HREF</B>=url
 <BR><B>ARCHIVE</B>=url
 <BR><B>CODEBASE</B>=url
 <BR><B>ID</B>=string
 <BR><B>SRC</B>=url</UL>
 </UL>
 Note: HREF takes precedence over SRC in nav4.</UL>
 <B>HEAD</B>
 <UL>/HEAD clears the "in_head" flag (but leaves the "in_body" flag alone.
 <BR>Text in head clears in_head, and set in_body true, just as if the author
 forgot the /HEAD tag.
 <BR>Attributes: none</UL>
 <B>HTML</B>
 <UL>Ignored.
 <BR>Attributes: none</UL>
 <B>STYLE</B>
 <UL>Allowed anywhere in the document. Note that entities are not parsed
 in the style tag's content.
 <BR>Attributes:
 <UL><B>LANGUAGE</B>=LiveScript|Mocha|JavaScript1.1|JavaScript1.2
 <BR><B>TYPE</B>="text/javascript" | "text/css"
 <BR><B>HREF</B>=url
 <BR><B>ARCHIVE</B>=url
 <BR><B>CODEBASE</B>=url
 <BR><B>ID</B>=string
 <BR><B>SRC</B>=url</UL>
 </UL>
 <B>FRAMESET</B>
 <UL>Frameset with rows=1 and cols=1 is ignored.
 <BR>Attributes:
 <UL><B>FRAMEBORDER</B>= no | 0 (zero) [default is no_edges=false]
 <BR><B>BORDER</B>= int [clamped: >= 0 &amp;&amp; &lt;= 100]
 <BR><B>BORDERCOLOR</B>= color
 <BR><B>ROWS</B>= pct-list
 <BR><B>COLS</B>= pct-list</UL>
 </UL>
 <B>FRAME</B>
 <UL>Border width of zero disables edges.
 <BR>Attributes:
 <UL><B>FRAMEBORDER</B>= no | 0 (zero) [default is framesets value]
 <BR><B>BORDER</B>= int [clamped; >= 0 &amp;&amp; &lt;= 100]
 <BR><B>BORDERCOLOR</B>= color
 <BR><B>NORESIZE</B>= true [default is false]
 <BR><B>SCROLLING</B>= yes | scroll | on | no | noscroll | off
 <BR><B>SRC</B>= url [clamped: prevent recursion by eliminating any anscestor
 references]
 <BR><B>NAME</B>= string
 <BR><B>MARGINWIDTH</B>= int (clamped: >= 1)
 <BR><B>MARGINHEIGHT</B>= int (clamped: >= 1)</UL>
 </UL>
 <B>NOFRAMES</B>
 <UL>Used when frames are disabled or for backrev browsers. Has no stylistic
 consequences.</UL>
 <H1>
 <HR WIDTH="100%">Body objects:</H1>
 &nbsp;<B>BODY</B>
 <UL>The tag is only processed on open tags and it is always processed.
 See ns\lib\layout\laytags.c, searching for "case P_BODY". During tag processing
 the in_head flag is set to false and the in_body flag is set to true. An
 attribute is ignored if the document already has that attribute set. Attributes
 can be set by style sheets, or by previous BODY tags. see <A HREF="../testhtml/head02.html">test
 head02.html</A>.
 <BR>Attributes:
 <UL><B>MARGINWIDTH</B>=int [clamped: >= 0 &amp;&amp; &lt; (windowWidth/2
 - 1)]
 <BR><B>MARGINHEIGHT</B>=int [clamped: >= 0 &amp;&amp; &lt; (windowHeight/2
 - 1)]
 <BR><B>BACKGROUND</B>=url
 <BR><B>BGCOLOR</B>=colorspec
 <BR><B>TEXT</B>=colorspec
 <BR><B>LINK</B>=colorspec
 <BR><B>VLINK</B>=colorspec
 <BR><B>ALINK</B>=colorspec
 <BR><B>ONLOAD, ONUNLOAD, UNFOCUS, ONBLUR, ONHELP</B>=script
 <BR><B>ID</B>=string</UL>
 </UL>
 <B>LAYER, ILAYER</B>
 <UL>Open layer/ilayer tag automaticly close out an open form if one is
 open. It does something to the soft linebreak state too.
 <BR>Attributes:
 <UL><B>LEFT</B>=value-or-pct (pct of <TT>right-left</TT> margin)
 <BR><B>PAGEX</B>=x (if no LEFT)
 <BR><B>TOP</B>=value-or-pct
 <BR><B>PAGEY</B>=y (if no TOP)
 <BR><B>CLIP</B>=clip
 <BR><B>WIDTH</B>=value-or-pct (pct of <TT>right-left</TT> margin)
 <BR><B>HEIGHT</B>=value-or-pct
 <BR><B>OVERFLOW</B>=string
 <BR><B>NAME</B>=string
 <BR><B>ID</B>=string
 <BR><B>ABOVE</B>=string
 <BR><B>BELOW</B>=string
 <BR><B>ZINDEX</B>=int [any value]
 <BR><B>VISIBILITY</B>=string
 <BR><B>BGCOLOR</B>=colorspec
 <BR><B>BACKGROUND</B>=url</UL>
 </UL>
 <B>NOLAYER</B>
 <UL>Container for content which is used when layers are disabled or unsupported.
 The content has no style consequences (though it could if somebody stuck
 in some CSS1 style rules for it).</UL>
 <B>P</B>
 <UL>Closes the paragraph. If the attribute is present then an alignment
 gets pushed on the alignment stack. All values are supported by nav4.
 <BR>Attributes:
 <UL><B>ALIGN</B>=divalign</UL>
 </UL>
 <B>ADDRESS</B>
 <UL>There are no attributes. ADDRESS closes out the open paragraph. The
 open tag does a conditional soft line break and then pushes a merge of
 the current style with italics enabled onto the style stack. The close
 always pop the style stack and also does a conditional soft line break.</UL>
 <B>PLAINTEXT, XMP</B>
 <UL>PLAINTEXT causes the remaining content to no longer be parsed. XMP
 causes the content to not parse entities or other tags. The XMP can be
 closed by it's own tag (on any boundary); PLAINTEXT is not closed (html3.2
 allows it to be closed). Both tags change the style to a fixed font of
 a</UL>
 <B>LISTING</B>
 <UL>Closes the paragraph. Does a hard line break on open and close. Open
 pushes a fixed width font style of a particular font size on the style
 stack. The close tag pops the top of the style stack.
 <BR>Attributes: none</UL>
 <B>PRE</B>
 <UL>Closes the paragraph. The open tag does a hard line break. A fixed
 font style (unless VARIABLE is present) is pushed on the style stack. The
 close tag pops the top of the style stack. It also does a hard line break.
 <BR>Attributes:
 <UL><B>WRAP</B>
 <BR><B>COLS</B>=int [clamped: >= 0]
 <BR><B>TABSTOP</B>=int [clamped: >= 0; clamped value is replaced with default
 value]
 <BR><B>VARIABLE</B></UL>
 </UL>
 <B>NOBR</B>
 <UL>This tag doesn't nest. Instead it just sets or clears a flag in the
 state machine. It has no effect on any other state.</UL>
 <B>CENTER</B>
 <UL>Closes the paragraph. Always does a conditional soft line break. The
 open tag pushes an alignment on the aligment stack. The close tag pops
 the top alignment off.
 <BR>Attributes: none</UL>
 <B>DIV</B>
 <UL>Closes the paragraph. Always does a conditional soft line break. COLS
 defines the number of columns to layout in (like MULTICOL). The open tag
 pushes an alignment on the alignment stack (if COLS > 1 then it pretends
 to be a MULTICOL tag). The close tag pops an aligment from the alignment
 stack.
 <BR>Attributes:
 <UL><B>ALIGN</B>=divalign
 <BR><B>COLS</B>=int [if cols > 1 then DIV acts like a MULTICOL tag else
 DIV is just a container]
 <UL><B>GUTTER</B>= int (clamped: >= 1)
 <BR><B>WIDTH</B>= value-or-pct [pct of right-left margin; clamped >= 1/0
 (strange code)]</UL>
 </UL>
 </UL>
 <B>H1-H6</B>
 <UL>Closes the paragraph. The open tag does a hard line break and pushes
 a style item which enables bold and disables fixed and italic. The close
 tag always pops the top item from the style stack. It also does a hard
 line break. If the <B>ALIGN</B> attribute is present then the open tag
 pushes an alignment on the alignment stack. The close tag will look at
 the top of the alignment stack and if its a header of any kind (H1 through
 H6) then the alignment is popped. In either case the close tag also does
 a conditional soft line break (this happens before the hard line break).
 <BR>Attributes:
 <UL><B>ALIGN</B>=divalign</UL>
 </UL>
 A note regarding closing paragraphs: Any time a close paragraph is done
 (for any tag) if the top of the alignment stack has a tag named "P" then
 a conditional soft line break is done and the alignment is popped.
 <H3>
 <HR ALIGN=LEFT WIDTH="50%"></H3>
 <B>TABLE</B>
 <UL>Close the paragraph.
 <BR>Attributes:
 <UL><B>ALIGN=</B>left|right|center|abscenter
 <BR><B>BORDER</B>=int [clamped: if null then -1, if &lt; 1 then 1 ]
 <BR><B>BORDERCOLOR</B>=string [if not supplied then set to the text color
 ]
 <BR><B>VSPACE</B>=int [ clamped: >= 0 ]
 <BR><B>HSPACE</B>=int [ clamped: >= 0 ]
 <BR><B>BGCOLOR</B>=color
 <BR><B>BACKGROUND</B>=url
 <BR><B>WIDTH</B>=value-or-pct [ % of win.width minus margins; clamped:
 >= 0 ]
 <BR><B>HEIGHT</B>=value-or-pct [ % of win.height minus margins; clamped:
 >= 0 ]
 <BR><B>CELLPADDING</B>=int [clamped: >= 0; separate pads take precedence
 ]
 <BR><B>TOPPADDING</B>= int [clamped: >= 0 ]
 <BR><B>BOTTOMPADDING</B>= int [clamped: >= 0 ]
 <BR><B>LEFTPADDING</B>= int [clamped: >= 0 ]
 <BR><B>RIGHTPADDING</B>= int [clamped: >= 0 ]
 <BR><B>CELLSPACING</B>= int [clamped: >= 0 ]
 <BR><B>COLS</B>=int [clamped: >= 0]</UL>
 The code supports more attributes in the Table attribute handler than it
 does in the code that gets the attributes from the tag! They are border_top,
 border_left, border_right, border_bottom, border_style (defaults to outset;
 allows for outset/dotted/none/dashed/solid/double/groove/ridge/inset).</UL>
 <B>TR</B>
 <UL>Open TR automatically closes an open table row (and an open table cell
 if one is open). It also automatically closes a CAPTION tag.
 <BR>Attributes:
 <UL><B>BGCOLOR</B>=color
 <BR><B>BACKGROUND</B>=url
 <BR><B>VALIGN</B>=top|bottom|middle|center(==middle)|baseline; default
 is top
 <BR><B>ALIGN</B>=left|right|middle|center(==middle); default is left</UL>
 </UL>
 <B>TH, TD</B>
 <UL>If no table then the tag is ignored (open or close). If no row is currently
 opened or the current row is current done (because of a &lt;/TR> tag) then
 a new row is begun. Oddly enough the tag parameters for the row come from
 the TH/TD tag in this case. An open of either of these tags will automatically
 close the previous cell.
 <BR>Attributes:
 <UL><B>COLSPAN</B>=int [clamped: >= 1 &amp;&amp; &lt;= 1000 ]
 <BR><B>ROWSPAN</B>=int [clamped: >= 1 &amp;&amp; &lt;= 10000 ]
 <BR><B>NOWRAP</B> [boolean: disables wrapping ]
 <BR><B>BGCOLOR</B>=color [default: inherit from the row; if not row then
 table; if not table then inherit from an outer table cell; this works because
 the style is flattened so the outer table cell will have a color]
 <BR><B>BACKGROUND</B>=url [same rules as bgcolor for inheritance; tile
 mode is inherited too and not settable by TH/TD attributes (have to use
 style sheets for that)]
 <BR><B>VALIGN</B>=top|bottom|middle|center(==middle)|baseline; default
 is top
 <BR><B>ALIGN</B>=left|right|middle|center(==middle); default is left
 <BR><B>WIDTH</B>=value-or-pct [ clamped: >= 0 ]
 <BR><B>HEIGHT</B>=value-or-pct [ clamped: >= 0 ]</UL>
 </UL>
 <B>CAPTION</B>
 <UL>An open caption tag will automatically close an open table row (and
 an open cell).
 <BR>Attributes:
 <UL><B>ALIGN</B>=bottom</UL>
 The code sets the vertical alignment to top w/o providing a mechanism for
 the user to set it (there is no VALIGN attribute).</UL>
 <B>MULTICOL</B>
 <UL>The open tag does a hard line break. The close tag checks to see if
 the state machine has an open multicol and if it does then it does a conditional
 soft line break and then continues to break until both margins are cleared
 of floating elements. It recomputes the margins based on the list indenting
 level (?). After the synthetic table is output the close tag does a hard
 line break.
 <P>This tag will treat the input as source for a table with one row and
 COLS columns. The data is laid out using the width divided by the number
 of columns. After the total height is known, the content is partitioned
 as evenly as possible between the columns in the table.
 <BR>Attributes:
 <UL><B>COLS</B>=int [clamped: values less than 2 cause the tag to be ignored]
 <BR><B>GUTTER</B>=int [clamped: >= 1]
 <BR><B>WIDTH</B>=value-or-pct [pct of right-left margin; clamped: >= 1/0
 (strange code)]</UL>
 </UL>
 <H3>
 <HR ALIGN=LEFT WIDTH="50%"></H3>
 <B>BLOCKQUOTE</B>
 <UL>Closes the paragraph. The open tag does a hard line break. A list with
 the empty-bullet style is pushed on the list stack (unless TYPE=cite/jwz
 then a styled list is pushed). The close tag pops any list and does a hard
 line break.
 <BR>Attributes:
 <UL><B>TYPE</B>=cite | jwz</UL>
 </UL>
 <B>UL, OL, MENU, DIR</B>
 <UL>For top-level lists (lists not in lists) a hard break is done on the
 open tag, otherwise a conditional-soft-break is done. Tag always does a
 close paragrah. The close tag does a conditional soft line break when nested;
 when not nested the close tag does a hard line break (even if no list is
 open). The open tag pushes the list on the list stack. The close tag pops
 any list off the list stack.
 <BR>Attributes:
 <UL><B>TYPE</B>= none | disc | circle | round | square | decimal | lower-roman
 | upper-roman | lower-alpha | upper-alpha | A | a | I | i [clamped: if
 none of the above is picked and OL then the bullet type is "number" otherwise
 the bullet type is "basic"]
 <BR><B>START</B>=int [clamped: >= 1]
 <BR><B>COMPACT</B></UL>
 </UL>
 <B>DL</B>
 <UL>Closes the paragraph. For the open tag, if the list is nested then
 a conditional soft line break is done otherwise a hard line break is done.
 The open tag pushes a list on the list stack. The close tag pops any list
 from the list stack. Closing the list acts like other lists closes.
 <BR>Attributes:
 <UL><B>COMPACT</B></UL>
 </UL>
 <B>LI</B>
 <UL>Closes the paragraph. The open tag does a conditional soft line break.
 Close tags are ignored (except for closing the paragraph).
 <BR>Attributes:
 <UL><B>TYPE</B>= A | a | I | i (if the containing list is an <B>OL</B>)
 <BR><B>TYPE</B>= round | circle | square (if the containing list is not
 <B>OL</B> and not <B>DL</B>)
 <BR><B>VALUE</B>=int [clamped: >= 1]</UL>
 The magellan html parser allows the full set of list item styles from the
 OL/DL tag instead of just the limited set that nav4 allows.</UL>
 <B>DD</B>
 <UL>Closes the paragraph. Close tags are ignored (except for closing the
 paragraph). DD outside a DL just advances the X coordinate of layout by
 a small constant. DD inside a DL does a conditional soft line break and
 other margin crud.
 <BR>Attributes: none.</UL>
 <B>DT</B>
 <UL>Closes the paragraph (open or close). Close tags are otherwise ignored.
 Does a conditional soft line break. Moves the X layout coordinate to the
 left margin.
 <BR>Attributes: none</UL>
 <H3>
 <HR ALIGN=LEFT WIDTH="50%"></H3>
 <B>A</B>
 <UL>Open anchors push a style on the style stack if the anchor has an <B>HREF</B>.
 Close anchors pop as many styles off the top of the style stack that are
 anchor tags (anchor tags don't nest in other words). In addition, any styles
 on the stack that have the ANCHOR bit set have it cleared and fiddle with
 the foreground and background colors.
 <BR>Attributes:
 <UL><B>NAME</B>=string
 <BR><B>HREF</B>=url
 <UL><B>TARGET</B>=target
 <BR><B>SUPPRESS</B>=true</UL>
 </UL>
 </UL>
 <B>STRIKE, S, TT, CODE, SAMPLE, KBD, B, STRONG, I, EM, VAR, CITE, BLINK,
 BIG, SMALL, U, INLINEINPUT, SPELL</B>
 <UL>The open tag pushes onto the style stack. The close tag always pops
 the top item from the style stack.
 <BR>Attributes: none</UL>
 <B>SUP, SUB</B>
 <UL>The open tag pushes a font size descrease on the style stack. The close
 tag always pops the top of the style stack. The open and close tag impacts
 the baselineThe only difference between SUP and SUB is how they impact
 the baseline. Note that the baseline information is forgotten after a line
 break; therefore a close SUP/SUB on the next line will do strange things.
 <BR>Attributes: none</UL>
 <B>SPAN</B>
 <UL>Ignored by the navigator.
 <BR>Attributes: none</UL>
 <B>FONT</B>
 <UL>The open font tag with no attributes resets the font size to the base
 font size. The open tag always pushes a style stack entry. The close tag
 always pops the top item off the style stack.
 <BR>Attributes:
 <UL><B>SIZE</B>=[+ int | - int | int ]&nbsp; [clamped: >=1 &amp;&amp; &lt;=
 ]
 <BR><B>POINT-SIZE=</B>[+ int | - int | int ] [clamped: >= 1 &amp;&amp;
 &lt;= 1600]
 <BR><B>FONT-WEIGHT</B>=[+ int | - int | int ] [clamped: >= 100 &amp;&amp;
 &lt;= 900]
 <BR><B>COLOR</B>=colorspec
 <BR><B>FACE</B>=string</UL>
 </UL>
 A note regarding the style stack: The pop of the stack checks to see if
 the top of the stack is an ANCHOR tag. If it is not an anchor then the
 top item is unconditionally popped. If the top of the style stack is an
 anchor tag then the code searches for either the bottom of the stack or
 the first style stack entry not created by an anchor tag. If the entry
 is followed by another entry then the entry is removed from the stack (an
 out-of-order pop in other words). In this case the anchor style stack entry
 is left untouched.
 <H3>
 <HR ALIGN=LEFT WIDTH="50%"></H3>
 <B>text, entities</B>
 <UL>These are basic content objects that get fed directly to the output.
 In navigator the text is processed by doing line-breaking (entities have
 been converted to text already by the parser). The line-breaking is controlled
 by the margin settings and the list depth, the floating elements, the style
 attributes (font size, etc.), the preformatted flag, the no-break flag
 and so on.</UL>
 <B>IMG, IMAGE</B>
 <UL>Close tag is ignored.
 <BR>Attributes:
 <UL><B>ISMAP</B>
 <BR><B>USEMAP</B>=url
 <BR><B>ALIGN</B>=alignparam
 <BR><B>SRC</B>=url [ whitespace is stripped ]
 <BR><B>LOWSRC</B>=url
 <BR><B>ALT</B>=string
 <BR><B>WIDTH</B>=value-or-pct (pct of <TT>right-left</TT> width)
 <BR><B>HEIGHT</B>=value-or-pct (pct of window height)
 <BR><B>BORDER</B>=int [clamped: >= 0]
 <BR><B>VSPACE</B>=int [clamped: >= 0]
 <BR><B>HSPACE</B>=int [clamped: >= 0]
 <BR><B>SUPPRESS</B>=true | false (only in blocked image layout???)</UL>
 </UL>
 <B>HR</B>
 <UL>Closes the paragraph. If an open tag then does a conditional soft line
 break. The rule inherits alignment from the parent container unless there
 is no container (then it's centered) or if the tag defines it's own alignment.
 After the object is inserted into the layout stream a soft line break is
 inserted as well.
 <BR>Attributes:
 <UL><B>ALIGN</B>=divalign (sort of; in laytags.c it's divalign; in layhrule.c
 it's left or right only)
 <BR><B>SIZE</B>=int (1 to 100 inclusive)
 <BR><B>WIDTH</B>=val-or-pct (pct of <TT>right-left</TT> width)
 <BR><B>NOSHADE</B></UL>
 </UL>
 <B>BR</B>
 <UL>Does an unconditional soft break. If clear is set then it will also
 soft break until either the left or right or both margins are clear of
 floating elements. Note that<FONT COLOR="#0000FF"> /BR == BR!</FONT>
 <BR>Attributes:
 <UL><B>CLEAR</B>=left | right | all | both</UL>
 </UL>
 <B>WBR</B>
 <UL>Soft word break.
 <BR>Attributes: none</UL>
 <B>EMBED</B>
 <UL>Close tag does nothing. Embed's operate inline just like images (they
 don't close the paragraph).
 <BR>Attributes:
 <UL><B>HIDDEN</B>=no | false | off
 <BR><B>ALIGN</B>=alignparam
 <BR><B>SRC</B>=url
 <BR><B>WIDTH</B>=val-or-pct (pct of <TT>right-left</TT> width)
 <BR><B>HEIGHT</B>=val-of-pct; if val is &lt; 1 (sometimes) the element
 gets HIDDEN automatically
 <BR><B>BORDER</B>=int (unsupported by navigator)
 <BR><B>VSPACE</B>=int [clamped: >= 0]
 <BR><B>HSPACE</B>=int [clamped: >= 0]</UL>
 </UL>
 <B>NOEBMED</B>
 <UL>Used when EMBED's are disabled. It is a container for regular content
 that has no stylistic consequences (no line breaking, no style stack effect,
 etc.).</UL>
 <B>APPLET</B>
 <UL>Applet tags don't nest (there is a notion of current_applet). The open
 tag automatically closes an open applet tag.
 <BR>Attributes:
 <UL><B>ALIGN</B>=alignparam
 <BR><B>CODE</B>=string
 <BR><B>CODEBASE</B>=string
 <BR><B>ARCHIVE</B>=string
 <BR><B>MAYSCRIPT</B>
 <BR><B>NAME</B>=string [clamped: white space is stripped out]
 <BR><B>WIDTH</B>=value-or-pct [pct of right-left width; clamped: >= 1]
 <BR><B>HEIGHT</B>=value-or-pct [pct of window height; clamped >= 1]
 <BR><B>BORDER</B>=int [clamped: >= 0]
 <BR><B>HSPACE</B>=int [clamped: >= 0]
 <BR><B>VSPACE</B>=int [clamped: >= 0]</UL>
 If no width is provided:
 <UL>if a height was provided, use the height. Otherwise, use 90% of the
 window width if percentage widths are allowed, otherwise use a value of
 .
 <BR>&nbsp;</UL>
 If no height is provided:
 <UL>if a width was provided, use the width. Otherwise, use 50% of the window
 height if percentage widths are allowed, otherwise use a value of 400.</UL>
 If the applet is hidden, then the widht/height get forced to zero.</UL>
 <B>PARAM</B>
 <UL>The param tag is supported when contained by the APPLET tag or the
 OBJECT tag. It has no stylistic consequences. The attribute values from
 the tag are passed to the containing APPLET or OBJECT. Note that <FONT COLOR="#0000FF">/PARAM
 == PARAM</FONT>.
 <BR>Attributes:
 <UL><B>NAME</B>=string [clamped: white space is stripped out]
 <BR><B>VALUE</B>=string [clamped: white space is stripped out]</UL>
 White space being stripped is done as follows: leading and trailing whitespace
 is removed. Any embedded whitespace is left alone except if it's a non-space
 whitespace in which case it is removed.</UL>
 <B>OBJECT</B>
 <UL>The open tag pushes an object onto the object stack. The close tag
 pops from the object stack. I don't understand how the data stuff works.
 <BR>Attributes:
 <UL><B>CLASSID</B>=string (clsid:, java:, javaprogram:, javabean: are the
 supported prefixes; maybe it's a url if no prefix shown?)
 <BR><B>TYPE</B>=string (a mime type)
 <BR><B>DATA</B>=string (data: prefix mentions a url)</UL>
 There are more attributes that depend on the type of object being embedded
 in the page. If the object is a java bean (?) then the applet parameters
 are supported:
 <UL>CLASSID
 <BR>HIDDEN
 <BR>ALIGN
 <BR>CLASSID (instead of CODE)
 <BR>CODEBASE
 <BR>ARCHIVE
 <BR>MAYSCRIPT
 <BR>ID (applets use NAME)
 <BR>WIDTH
 <BR>HEIGHT
 <BR>BORDER
 <BR>HSPACE
 <BR>VSPACE</UL>
 </UL>
 <B>MAP</B>
 <UL>The open tag automatically closes an open map (maps don't nest). There
 is no stylistic consequence of the map nor does it provide any visible
 presentation in the normal layout case (an editor would do something different).
 The map can be declared anywhere in the document.
 <BR>Attributes:
 <UL><B>NAME</B>=string [clamped: white space is stripped out]</UL>
 </UL>
 <B>AREA</B>
 <UL>Does nothing if there is no current map or the tag is a close tag.
 <BR>Attributes:
 <UL><B>SHAPE</B>=default | rect | circle | poly | polygon
 <BR><B>ALT</B>=string [clamped: newlines are stripped]
 <BR><B>COORDS</B>=coord-list
 <BR><B>HREF=</B>url
 <UL><B>TARGET</B>=target (only if HREF is specified)</UL>
 <B>SUPPRESS</B></UL>
 </UL>
 <B>SERVER</B>
 <UL>A container for server-side javascript. Not evaluated by the client
 (parsed and ignored). Note: The navigator parser doesn't expand entities
 in a <B>SERVER </B>tag.</UL>
 <B>SPACER</B>
 <UL>Close tag is ignored. Open tag provides whitespace during layout: <B>TYPE</B>=line/vert/vertical
 causes a conditional soft line break and then adds <B>SIZE </B>to the Y
 layout coordinate. <B>TYPE</B>=word causes a conditional soft word break
 and then adds <B>SIZE </B>to the X layout coordinate. <B>TYPE</B>=block
 causes <FONT COLOR="#DD0000">blockish </FONT>layout stuff to happen.
 <BR>Attributes:
 <UL><B>TYPE</B>=line | vert | vertical | block (default: word)
 <UL><B>ALIGN</B>=alignparam (these 3 params are only for <B>TYPE</B>=block)
 <BR><B>WIDTH</B>=value-or-pct
 <BR><B>HEIGHT</B>=value-or-pct</UL>
 <B>SIZE</B>=int [clampled: >= 0]</UL>
 </UL>
 <H3>
 <HR ALIGN=LEFT WIDTH="50%"></H3>
 <B>SCRIPT</B>
 <UL>Note: The navigator parser doesn't expand entities in a SCRIPT tag.
 <BR>Attributes:
 <UL><B>LANGUAGE</B>=LiveScript | Mocha | JavaScript1.1 | JavaScript1.2
 <BR><B>TYPE</B>="text/javascript" | "text/css"
 <BR><B>HREF</B>=url
 <BR><B>ARCHIVE</B>=url
 <BR><B>CODEBASE</B>=url
 <BR><B>ID</B>=string
 <BR><B>SRC</B>=url</UL>
 </UL>
 <B>NOSCRIPT</B>
 <UL>Used when scripting is off or by backrev browsers. It is a container
 that has no stylistic consequences.</UL>
 <H3>
 <HR ALIGN=LEFT WIDTH="50%"></H3>
 <B>FORM&nbsp;</B>
 <UL>Attributes:
 <UL><B>ACTION</B>=href
 <BR><B>ENCODING</B>=string
 <BR><B>TARGET</B>=string
 <BR><B>METHOD</B>=get | post</UL>
 </UL>
 <B>ISINDEX&nbsp;</B>
 <UL>This tag is a shortcut for creating a form element with a submit button
 and a single text field. If the PROMPT attribute is not present in the
 tag then the value used is <B>"This is a searchable index. Enter search
 keywords:"</B>.
 <P>Attributes:
 <UL><B>PROMPT</B>=string
 <BR><B>ACTION</B>=href
 <BR><B>ENCODING</B>=string
 <BR><B>TARGET</B>=string
 <BR><B>METHOD</B>=get | post</UL>
 </UL>
 <B>INPUT&nbsp;</B>
 <UL>Attributes vary according to type:
 <UL><B>TYPE</B>= text | radio | checkbox | hidden | submit | reset | password
 | button | image | file | jot | readonly | object
 <BR><B>NAME</B>= string
 <BR>&nbsp;</UL>
 <B>TYPE</B>=image
 <UL>attributes are from the IMG tag (!)</UL>
 <B>TYPE</B>= text | password | file
 <UL>font style is forced to fixed
 <BR><B>VALUE</B>= string
 <BR><B>SIZE</B>= int (clamped; >= 1)
 <BR><B>MAXLENGTH</B>= int (not clamped!)</UL>
 <B>TYPE</B>= submit | reset | button | hidden | readonly
 <UL><B>VALUE</B>=string; default if no value to the attribute varies according
 to the type:
 <UL><B>submit</B> -> "Submit Query"
 <BR><B>reset</B> -> "Reset"
 <BR>others -> "&nbsp; " (2 spaces)
 <BR>Note also that the value has newlines stripped from it</UL>
 <B>WIDTH</B>=int (clamped >=0 &amp;&amp; &lt;= 1000) (only for submit,
 reset or button)
 <BR><B>HEIGHT</B>=int (clamped >=0 &amp;&amp; &lt;= 1000) (only for submit,
 reset or button)</UL>
 <B>TYPE</B>=radio | checkbox
 <UL><B>CHECKED</B> (flag - if present then set to true)
 <BR><B>VALUE</B>= string (the default value is "on")</UL>
 </UL>
 <B>SELECT&nbsp;</B>
 <UL>Attributes:
 <UL><B>MULTIPLE</B> (boolean)
 <BR><B>SIZE</B>= int (clamped >= 1)
 <BR><B>NAME=</B> string
 <BR><B>WIDTH</B>= int (clampled >= 0 &amp;&amp; &lt;= 1000)
 <BR><B>HEIGHT</B>= int (clamped >= 0 &amp;&amp; &lt;= 1000; only examined
 for single entry lists (!multiple || size==1))</UL>
 </UL>
 <B>OPTION&nbsp;</B>
 <UL>Lives inside the SELECT tag (ignored otherwise).
 <BR>Attributes:
 <UL><B>VALUE</B>=string
 <BR><B>SELECTED</B> boolean</UL>
 </UL>
 <B>TEXTAREA&nbsp;</B>
 <UL>Attributes:
 <UL><B>NAME</B>=string
 <BR><B>ROWS</B>=int (clamped; >= 1)
 <BR><B>COLS</B>=int (clamped; >= 1)
 <BR><B>WRAP</B>= off | hard | soft (default is off; any value which is
 not known turns into soft)</UL>
 </UL>
 <B>KEYGEN&nbsp;</B>
 <UL>Attributes:
 <UL><B>NAME</B>=string
 <BR><B>CHALLENGE</B>=string
 <BR><B>PQG</B>=string
 <BR><B>KEYTYPE</B>=string</UL>
 </UL>
 <H3>
 <HR ALIGN=LEFT WIDTH="50%"></H3>
 <B>BASEFONT&nbsp;</B>
 <UL>Sets the base font value which +/- size values in FONT tags are relative
 to.
 <BR>Attributes:
 <UL>SIZE=+ int | - int | int (just like FONT)</UL>
 </UL>
 <H2>
 <HR WIDTH="100%">Unsupported</H2>
 <B>NSCP_CLOSE, NSCP_OPEN, NSCP_REBLOCK, MQUOTE, CELL, SUBDOC, CERTIFICATE,
 INLINEINPUTTHICK, INLINEINPUTDOTTED, COLORMAP, HYPE, SPELL, NSDT</B>
 <UL>These tags are unsupported because they are used internally by netscape
 and are never seen in real content. If somebody does use them between 4.0
 and magellan, tough beans. We never documented them so they lose.</UL>
 </BODY>
 </HTML>

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