troggle-unchained/media/CodeMirror-0.62/manual.html
2009-06-28 21:22:16 +01:00

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<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>CodeMirror user manual</title>
<link rel="stylesheet" type="text/css" href="css/docs.css"/>
</head>
<body>
<h1 class="underline">CodeMirror user manual</h1>
<h2>Contents</h2>
<ul>
<li><a href="#useage">Basic Useage</a></li>
<li><a href="#configuration">Configuration</a></li>
<li><a href="#parsers">Parsers</a></li>
<li><a href="#programming">Programming Interface</a></li>
<li><a href="#writeparser">Writing a Parser</a></li>
</ul>
<h2 id="useage">Basic Usage</h2>
<p>Inside the editor, the tab key is used to re-indent the current
selection (or the current line when nothing is selected), and
pressing enter will, apart from inserting a line break,
automatically indent the new line. Pressing control-enter will
cause the whole buffer to be re-coloured, which can be helpful
when some colouring has become out-of-date without the editor
noticing it.</p>
<p>The editor sports an undo/redo system, accessible with
control-z (undo) and control-y (redo). Safari will not allow
client scripts to capture control-z presses, but you can use
control-backspace instead on that browser.</p>
<p>The key-combination control-[ triggers a paren-blink: If the
cursor is directly after a '(', ')', '[', ']', '{', or '}', the
editor looks for the matching character, and highlights these
characters for a moment. There is an option to enable this to
happen any time the user types something or moves the cursor.</p>
<p>To use CodeMirror in a document, you should add a script tag to
load <a href="js/codemirror.js"><code>codemirror.js</code></a>. This
adds two objects to your environment, <code>CodeMirror</code> and
<code>CodeMirrorConfig</code>. The first is the interface to the
editor, the second can be used to configure it. (Note that this is
the only name-space pollution you can expect from CodeMirror --
all other cruft is kept inside the IFRAMEs that it creates when
you open an editor.)</p>
<p>To add an editor to a document, you must choose a place, a
parser, and a style-sheet for it. For example, to append an
XML editor to the body of the document, you do:</p>
<pre class="code">var editor = new CodeMirror(document.body, {
parserfile: "parsexml.js",
stylesheet: "xmlcolors.css"
});</pre>
<p>The first argument to the <code>CodeMirror</code> constructor
can be a DOM node, in which case the editor gets appended to that
node, or a function, which will be called with the IFRAME node as
argument, and which is expected to place that node somewhere in
the document.</p>
<p>The second (optional) argument is an object that specifies
options. A set of default options (see below) is present in the
<code>CodeMirrorConfig</code> object, but each instance of the
editor can be given a set of specific options to override these
defaults. In this case, we specified that the parser should be
loaded from the <a
href="js/parsexml.js"><code>"parsexml.js"</code></a> file, and
that <a href="css/xmlcolors.css"><code>"xmlcolors.css"</code></a>
should be used to specify the colours of the code.</p>
<p>Another example:</p>
<pre class="code">var editor = new CodeMirror(CodeMirror.replace("inputfield"), {
parserfile: ["tokenizejavascript.js", "parsejavascript.js"],
path: "lib/codemirror/js/",
stylesheet: "lib/codemirror/css/jscolors.css",
content: document.getElementById("inputfield").value
});</pre>
<p>Here we use the utility function
<code>CodeMirror.replace</code> to create a function that will
replace a node in the current document (given either directly or
by ID) with the editor. We also select the JavaScript parser this
time, and give a <code>path</code> option to tell the editor that
its files are not located in the same directory as the current
HTML page, but in <code>"lib/codemirror/"</code>.</p>
<p>There is a function
<code>CodeMirror.isProbablySupported()</code> that causes some
1998-style browser detection to happen, returning
<code>false</code> if CodeMirror is probably not supported on the
browser, <code>true</code> if it probably is, and
<code>null</code> if it has no idea. As the name suggests, this is
not something you can rely on, but it's usually better than
nothing.</p>
<p>Another utility function, <code>CodeMirror.fromTextArea</code>,
will, given a textarea node or the id of such a node, hide the
textarea and replace it with a CodeMirror frame. If the textarea
was part of a form, an <code>onsubmit</code> handler will be
registered with this form, which will load the content of the
editor into the textarea, so that it can be submitted as normal.
This function optionally takes a configuration object as second
argument.</p>
<pre class="code">var editor = CodeMirror.fromTextArea("inputfield", {
parserfile: ["tokenizejavascript.js", "parsejavascript.js"],
path: "lib/codemirror/js/",
stylesheet: "lib/codemirror/css/jscolors.css"
});</pre>
<p>The reason that the script path has to be configured is that
CodeMirror will load in a bunch of extra files when an editor is
created (the parser script, among others). To be able to do this,
it has to know where to find them. These are all the JavaScript
files that are part of CodeMirror itself:</p>
<dl>
<dt><a href="js/codemirror.js"><code>codemirror.js</code></a></dt>
<dd>Main interface, takes care of default configuration and the
definition of editor frames. Include this in your HTML
document.</dd>
<dt><a href="js/editor.js"><code>editor.js</code></a></dt> <dd>The
code that takes care of reacting to user input, colouring text,
and indenting lines.</dd>
<dt><a href="js/util.js"><code>util.js</code></a></dt> <dd>A few
generic utility functions.</dd>
<dt><a
href="js/undo.js"><code>undo.js</code></a></dt>
<dd>Implements the undo history for the editor.</dd>
<dt><a
href="js/stringstream.js"><code>stringstream.js</code></a></dt>
<dd>Objects for wrapping the textual input to the parser.</dd>
<dt><a href="js/select.js"><code>select.js</code></a></dt> <dd>Some
helper utilities for working with selected text and cursor
positions.</dd>
<dt><a href="js/tokenize.js"><code>tokenize.js</code></a></dt>
<dd>Helper framework for writing tokenisers.</dd>
</dl>
<p>Most of these are rather full of comments, which can be useful
when you are trying to figure out how they work, but wastes a lot
of bandwidth in a production system. Take a look at the
description of the <code>basefiles</code> option below if you want
to concatenate and minimise the library.</p>
<p>Apart from these, there are files that implement the various
parsers. These all start with either <code>parse</code> or
<code>tokenize</code>.</p>
<h2 id="configuration">Configuration</h2>
<p>There are three ways to configure CodeMirror:</p>
<ul>
<li>If you define a global <code>CodeMirrorConfig</code> object
before loading <a
href="js/codemirror.js"><code>codemirror.js</code></a>, the
configuration options in that object will override the
defaults.</li>
<li>By assigning to the properties of the
<code>CodeMirrorConfig</code> object, configuration defaults can
be overridden after loading <a
href="js/codemirror.js"><code>codemirror.js</code></a>.</li>
<li>The <code>CodeMirror</code> constructor can be given a second
argument, an object, which will override some options for just
that editor. Options not mentioned in this object will default to
the values in the <code>CodeMirrorConfig</code> object.</li>
</ul>
<p>The options that can be specified are these (most have sensible
defaults specified in <a
href="js/codemirror.js"><code>codemirror.js</code></a>):</p>
<dl>
<dt><code>stylesheet</code></dt><dd>The file name of the style-sheet
that should be used to colour the code in the editor frame. See <a
href="css/jscolors.css"><code>jscolors.css</code></a> for an
example.</dd>
<dt><code>path</code></dt><dd>The path that is prefixed to
script file names when they are loaded into an IFRAME. (Note that
this is not applied to the style-sheet file name.)</dd>
<dt><code>parserfile</code></dt><dd>A file name string, or an
array of strings that name the files containing the parser. See
below for the interface that such a parser should
implement.</dd>
<dt><code>basefiles</code></dt><dd>An array of strings naming
the files containing the base CodeMirror functionality. Defaults
to <code>["util.js", "stringstream.js", "select.js", "undo.js",
"editor.js", "tokenize.js"]</code>, but if you put them all into
a single file to reduce latency, or add some functionality, you
might have to adjust that.</dd>
<dt><code>iframeClass</code></dt><dd>Set this to a string to
give the IFRAME node created for the editor a custom CSS class.
Defaults to <code>null</code>.</dd>
<dt><code>passDelay</code></dt><dd>Gives the amount of
milliseconds between colouring passes. Defaults to 200.</dd>
<dt><code>passTime</code></dt><dd>Specifies the maximum amount
of time that the highlighter will spend in one shot. Setting
this too high will cause the editor to 'freeze' the browser for
noticeable intervals. Defaults to 50.</dd>
<dt><code>continuousScanning</code></dt><dd>Configure continuous
scanning of the document. When <code>false</code>, scanning is
disabled. When set to a number, say <code>N</code>, a
'background' process will scan the document for
<code>passTime</code> (see above) milliseconds every
<code>N</code> milliseconds, regardless of whether anything
changed. This makes sure non-local changes propagate through the
document, and will help keep everything consistent. It does add
extra processing cost, even for an idle editor. Default value is
<code>false</code>.</dd>
<dt><code>autoMatchParens</code></dt><dd>When <code>true</code>,
will cause parens to be matched every time a key is pressed or
the user clicks on the document. Defaults to <code>false</code>.
Might be expensive for big documents.</dd>
<dt><code>saveFunction</code></dt><dd>If given a function
value, that function will be invoked when the user presses
control-s. You should advise your Opera users to use
control-shift-s instead, since plain control-s will bring up the
'save page' dialog. Defaults to <code>null</code>.</dd>
<dt><code>undoDepth</code></dt><dd>Maximum length of the undo
history. Default is 50.</dd>
<dt><code>onChange</code></dt><dd>An optional function of zero
arguments that gets called whenever the document is changed.
Happens at undo-commit time, not instantaniously.</dd>
<dt><code>undoDelay</code></dt><dd>When nothing is done in the
editor for this amount of milliseconds, pending changes get
added to the undo history. Setting this lower will give the undo
functionality a finer granularity. Defaults to 800.</dd>
<dt><code>width</code>, <code>height</code></dt><dd>The size of
the editor frame, given as a style-sheet quantities (for example
<code>"600px"</code> or <code>"100%"</code>).</dd>
<dt><code>disableSpellcheck</code></dt><dd>Should the editor
disable spell-checking on browsers that support it (Firefox 2+).
Default is <code>true</code>, since for most code spell-checking
is useless.</dd>
<dt><code>textWrapping</code></dt><dd>Can be used to disable or
enable text-wrapping in the editor frame. Default is
<code>true</code>.</dd>
<dt><code>lineNumbers</code></dt><dd>Show line numbers to the
left of the editor. This requires you to specify a style for the
<code>CodeMirror-line-numbers</code> CSS class (in the outer
document) to configure the width, font, colors, etcetera for the
line-number DIV. You have to make sure that lines in the
numbering element have the same height as lines in the editor.
This is most easily done by giving them both the same font and
an absolute ('pt' or 'px') font size. This option defaults to
<code>false</code>. When enabling this, you have to disable
<code>textWrapping</code>, since the line numbers don't take
wrapped lines into account.</dd>
<dt><code>indentUnit</code></dt><dd>An integer that specifies
the amount of spaces one 'level' of indentation should add.
Default is <code>2</code>.</dd>
<dt><code>tabMode</code></dt><dd>Determines what the effect of
pressing tab is. Possibilities are:
<dl>
<dt><code>"indent"</code></dt><dd>The default. Causes tab to
adjust the indentation of the selection or current line using
the parser's rules.</dd>
<dt><code>"spaces"</code></dt><dd>Pressing tab simply inserts
four spaces.</dd>
<dt><code>"default"</code></dt><dd>CodeMirror does not
interfere with the tab key, but leaves it to the browser to
handle it. Binds shift-space to regular indentation
behaviour.</dd>
<dt><code>"shift"</code></dt><dd>Pressing tab indents the
current line (or selection) one <code>indentUnit</code>
deeper, pressing shift-tab or ctrl-tab (whichever your browser
does not interfere with), un-indents it.</dd>
</dl></dd>
<dt><code>reindentOnLoad</code></dt><dd>When <code>true</code>,
this causes the content of the editor to be reindented
immediately when the editor loads. Defaults to
<code>false</code>.</dd>
<dt><code>readOnly</code></dt><dd>When set to <code>true</code>,
the document is not editable.</dd>
<dt><code>initCallback</code></dt><dd>If set to a function, this
will be called (with the editor object as its argument) after
the editor has finished initialising.</dd>
<dt><code>cursorActivity</code></dt><dd>A function that is
called every time the cursor moves, with the top-level node that
the cursor is inside or next to as an argument. Can be used to
have some controls react to the context of the cursor.</dd>
<dt><code>activeTokens</code></dt><dd>Can be set to a function
that will be called with <code>(spanNode, tokenObject,
editor)</code> arguments whenever a new token node is being
added to the document. Can be used to do things like add event
handlers to nodes. Should <em>not</em> change the DOM structure
of the node (so no turning the span into a link), since this
will greatly confuse the editor.</dd>
<dt id="parserConfig"><code>parserConfig</code></dt><dd>An
object value that is passed along to the parser to configure it.
What this object should look like depends on the parser
used.</dd>
<dt><code>content</code></dt><dd>The starting content of the
editor. You'll probably not want to provide a global default for
this, but add it to the <code>options</code> object passed to
individual editors as they are created.</dd>
</dl>
<h2 id="parsers">Parsers</h2>
<p>(If you want to use a CodeMirror parser to highlight a piece of
text, without creating an editor, see <a
href="highlight.html">this example</a>, and the <code><a
href="js/highlight.js">highlight.js</a></code> script.)</p>
<p>The following parsers come with the distribution of CodeMirror:</p>
<dl>
<dt><code><a href="js/parsexml.js">parsexml.js</a></code> (<a
href="htmltest.html">demo</a>)</dt><dd>A HTML/XML parser. Takes
a <code>useHTMLKludges</code> configuration option (see the
<code><a href="#parserConfig">parserConfig</a></code> option
above), which specifies whether the content of the editor is
HTML or XML, and things like self-closing tags (<code>br</code>,
<code>img</code>) exist. This defaults to <code>true</code>.
Example colours for the styles that this parser uses are defined
in <code><a
href="css/xmlcolors.css">css/xmlcolors.css</a></code>.</dd>
<dt><code><a
href="js/tokenizejavascript.js">tokenizejavascript.js</a></code>,
<code><a
href="js/parsejavascript.js">parseejavascript.js</a></code> (<a
href="jstest.html">demo</a>)</dt><dd>The JavaScript parser.
Example colours in <code><a
href="css/jscolors.css">css/jscolors.css</a></code></dd>
<dt><code><a href="js/parsecss.js">parsecss.js</a></code> (<a
href="csstest.html">demo</a>)</dt><dd>A CSS parser. Styles in
<code><a
href="css/csscolors.css">css/csscolors.css</a></code></dd>
<dt><code><a
href="js/parsehtmlmixed.js">parsehtmlmixed.js</a></code> (<a
href="mixedtest.html">demo</a>)</dt><dd>A mixed-mode HTML
parser. Requires the XML, JavaScript, and CSS parsers to also be
loaded, so your <code>parserfile</code> option looks something
like <code>["parsexml.js", "parsecss.js",
"tokenizejavascript.js", "parsejavascript.js",
"parsehtmlmixed.js"]</code>.</dd>
<dt><code><a href="js/parsesparql.js">parsesparql.js</a></code>
(<a href="sparqltest.html">demo</a>)</dt><dd>Parses the <a
href="http://en.wikipedia.org/wiki/SPARQL">SPARQL</a> query
language. Example styles in <code><a
href="css/sparqlcolors.css">css/sparqlcolors.css</a></code></dd>
<dt><code><a
href="js/parsedummy.js">parsedummy.js</a></code></dt><dd>A
'dummy' parser to make it possible to edit plain text, or
documents for which no suitable parser exists.</dd>
<dt><code><a
href="contrib/php/js/parsephp.js">contrib/php/js/parsephp.js</a></code>
(<a href="contrib/php/index.html">demo</a>)</dt><dd>PHP
parser.</dd>
<dt><code><a
href="contrib/python/js/parsepython.js">contrib/python/js/parsepython.js</a></code>
(<a href="contrib/python/index.html">demo</a>)</dt><dd>Python
parser.</dd>
<dt><code><a href="contrib/lua/js/parselua.js">contrib/lua/js/parselua.js</a></code>
(<a href="contrib/lua/index.html">demo</a>)</dt><dd>Lua
parser.</dd>
</dl>
<h2 id="programming">Programming Interface</h2>
<p>To be as flexible as possible, CodeMirror implements a very
plain editable field, without any accompanying buttons, bells, and
whistles. <code>CodeMirror</code> objects do, however, provide a
number of methods that make it possible to add extra functionality
around the editor. <a
href="js/mirrorframe.js"><code>mirrorframe.js</code></a> provides a
basic example of their usage.</p>
<dl>
<dt><code>getCode()</code> &#8594;
<code>string</code></dt><dd>Returns the current content of the
editor, as a string.</dd>
<dt><code>setCode(string)</code></dt><dd>Replaces the current
content of the editor with the given value.</dd>
<dt><code>focus()</code></dt><dd>Gives focus to the editor
frame.</dd>
<dt><code>currentLine()</code> &#8594;
<code>number</code></dt><dd>Returns the line on which the cursor
is currently sitting. <span class="warn">(Deprecated, see the
line-based interface below)</span></dd>
<dt><code>jumpToLine(number)</code></dt><dd>Moves the cursor to
the start of the given line. <span
class="warn">(Deprecated)</span></dd>
<dt><code>selection()</code> &#8594;
<code>string</code></dt><dd>Returns the text that is currently
selected in the editor.</dd>
<dt><code>replaceSelection(string)</code></dt><dd>Replaces the
currently selected text with the given string. Will also cause
the editor frame to gain focus.</dd>
<dt><code>reindent()</code></dt><dd>Automatically re-indent the
whole document.</dd>
<dt><code>reindentSelection()</code></dt><dd>Automatically
re-indent the selected lines.</dd>
<dt><code>getSearchCursor(string, atCursor)</code> &#8594;
<code>cursor</code></dt><dd>The first argument indicates the
string that should be searched for, and the second indicates
whether searching should start at the cursor (<code>true</code>)
or at the start of the document (<code>false</code>). Returns an
object that provides an interface for searching. Call its
<code>findNext()</code> method to search for an occurrence of
the given string. This returns <code>true</code> if something is
found, or <code>false</code> if the end of document is reached.
When an occurrence has been found, you can call
<code>select()</code> to select it, or
<code>replace(string)</code> to replace it with a given string.
Note that letting the user change the document, or
programmatically changing it in any way except for calling
<code>replace</code> on the cursor itself, might cause a cursor
object to skip back to the beginning of the document.</dd>
<dt><code>undo()</code></dt><dd>Undo one changeset, if available.</dd>
<dt><code>redo()</code></dt><dd>Redo one changeset, if available.</dd>
<dt><code>historySize() &#8594; object</code></dt><dd>Get a
<code>{undo, redo}</code> object holding the sizes of the undo
and redo histories.</dd>
<dt><code>clearHistory()</code></dt><dd>Drop all history
information.</dd>
<dt><code>grabKeys(callback, filter)</code></dt><dd>Route
keyboard input in the editor to a callback function. This
function is given a slightly normalised (see
<code>normalizeEvent</code> in <a
href="js/util.js"><code>util.js</code></a>) <code>keydown</code>
event object. If a second argument is given, this will be used
to determine which events to apply the callback to. It should
take a key code (as in <code>event.keyCode</code>), and return a
boolean, where <code>true</code> means the event should be
routed to the callback, and <code>false</code> leaves the key to
perform its normal behaviour.</dd>
<dt><code>ungrabKeys()</code></dt><dd>Revert the effect of
<code>grabKeys</code>.</dd>
<dt><code>setParser(name)</code></dt><dd>Change the active
parser. To use this you'll have to load more than one parser
(put the one you want to use as default at the end of the list).
Then call this function with a string containing the name of the
parser you want to switch to (see the parser script file to find
the name, it'll be something like <code>CSSParser</code>).</dd>
</dl>
<p>For detailed interaction with the content of the editor,
CodeMirror exposes a line-oriented interface, which allows you to
inspect and manipulate the document line by line. Line handles
should be considered opaque (they are in fact the <code>BR</code>
nodes at the start of the line), except that the value
<code>false</code> (but <em>not</em> <code>null</code>) always
denotes an invalid value. Since changing the document might cause
some line handles to become invalid, every function that takes
them as argument can throw
<code>CodeMirror.InvalidLineHandle</code>. These are the relevant
methods:</p>
<dl>
<dt><code>cursorPosition(start)</code> &#8594;
<code>object</code></dt><dd>Retrieve a <code>{line,
character}</code> object representing the cursor position.
<code>start</code> defaults to <code>true</code> and determines
if the startpoint or the endpoint of the selection is used.</dd>
<dt><code>firstLine()</code> &#8594;
<code>handle</code></dt><dd>Get the first line of the
document.</dd>
<dt><code>lastLine()</code> &#8594;
<code>handle</code></dt><dd>The last line.</dd>
<dt><code>nextLine(handle)</code> &#8594;
<code>handle</code></dt><dd>Get the line after the given one, or
<code>false</code> if that was the last line.</dd>
<dt><code>prevLine(handle)</code> &#8594;
<code>handle</code></dt><dd>Find the line before the given one,
return <code>false</code> if that was the first line.</dd>
<dt><code>nthLine(number)</code> &#8594;
<code>handle</code></dt><dd>Find the Nth line of the document.
Note that the first line counts as one, not zero. Returns
<code>false</code> if there is no such line.</dd>
<dt><code>lineContent(handle)</code> &#8594;
<code>string</code></dt><dd>Retrieve the content of the
line.</dd>
<dt><code>setLineContent(handle, string)</code></dt><dd>Replace
the content of the line with the given string.</dd>
<dt><code>lineNumber(handle)</code> &#8594;
<code>number</code></dt><dd>Ask which line of the document
(1-based) the given line is.</dd>
<dt><code>selectLines(startHandle, startOffset,
endHandle, endOffset)</code></dt><dd>Move the selection to a
specific point. <code>endHandle</code> and
<code>endOffset</code> can be omitted to just place the cursor
somewhere without selecting any text.</dd>
<dt><code>insertIntoLine(handle, position,
text)</code></dt><dd>Insert a piece of text into a line.
<code>position</code> can be an integer, specifying the position
in the line where the text should be inserted, or the string
<code>"end"</code>, for the end of the line.</dd>
</dl>
<h2 id="writeparser">Writing a Parser</h2>
<p>A parser is implemented by one or more files (see
<code>parserfile</code> above) which, when loaded, add a
<code>Parser</code> object to the <code>Editor</code> object
defined by <a href="js/editor.js"><code>editor.js</code></a>. This
object must support the following interface:</p>
<dl>
<dt><code>make(stream)</code></dt><dd>A function that, given a
string stream (see <a
href="js/stringstream.js"><code>stringstream.js</code></a>),
creates a parser. The behaviour of this parser is described
below.</dd>
<dt><code>electricChars</code></dt><dd>An optional string
containing the characters that, when typed, should cause the
indentation of the current line to be recomputed (for example
<code>"{}"</code> for c-like languages).</dd>
<dt><code>configure(object)</code></dt><dd>An optional function
that can be used to configure the parser. If it exists, and an
editor is given a <code>parserConfig</code> option, it will be
called with the value of that option.</dd>
<dt><code>firstIndentation(chars, current,
direction)</code></dt><dd>An optional function that is used to
determine the proper indentation of the first line of a
document. When not provided, <code>0</code> is used.</dd>
</dl>
<p>When the <code>make</code> method is called with a string
stream, it should return a MochiKit-style iterator: an object with
a <code>next</code> method, which will raise
<code>StopIteration</code> when it is at its end (see <a
href="http://bob.pythonmac.org/archives/2005/07/06/iteration-in-javascript/">this</a>
for details). This iterator, when called, will consume input from
the string stream, and produce a token object.</p>
<p>Token objects represent a single significant piece of the text
that is being edited. A token object must have a
<code>value</code> property holding the text it stands for, and a
<code>style</code> property with the CSS class that should be used
to colour this element. This can be anything, except that any
whitespace at the start of a line should <em>always</em> have
class <code>"whitespace"</code>: The editor must be able to
recognize these when it indents lines. Furthermore, each newline
character <em>must</em> have its own separate token, which has an
<code>indentation</code> property holding a function that can be
used to determine the proper indentation level for the next line.
This function optionally takes the text in the first token of the
next line, the current indentation of the line, and the
'direction' of the indentation as arguments, which it can use to
adjust the indentation level. The direction argument is only
useful for modes in which lines do not have a fixed indentation,
and can be modified by multiple tab presses. It is
<code>null</code> for 'default' indentations (like what happens
when the user presses enter), <code>true</code> for regular tab
presses, and <code>false</code> for control-tab or shift-tab.</p>
<p>So far this should be pretty easy. The hard part is that this
iterator must also have a <code>copy</code> method. This method,
called without arguments, returns a function representing the
current state of the parser. When this state function is later
called with a string stream as its argument, it returns a parser
object that resumes parsing using the old state and the new input
stream. It may assume that only one parser is active at a time,
and can clobber the state of the old parser if it wants.</p>
<p>For examples, see <a
href="js/parsejavascript.js"><code>parsejavascript.js</code></a>,
<a href="js/parsexml.js"><code>parsexml.js</code></a>, and <a
href="js/parsecss.js"><code>parsecss.js</code></a>.</p>
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