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editing.html
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editing.html
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<!DOCTYPE html><meta charset=utf-8>
<title>HTML Editing APIs</title>
<link href=http://www.whatwg.org/style/specification rel=stylesheet>
<style>
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</style>
<body class=draft>
<div class=head id=head>
<h1>HTML Editing APIs</h1>
<h2 class="no-num no-toc" id=work-in-progress-—-last-update-19-august-2011>Work in Progress — Last Update 19 August 2011</h2>
<dl>
<dt>Editor
<dd>Aryeh Gregor <<a href=mailto:ayg@aryeh.name>ayg@aryeh.name</a>>
<dt>Latest version
<dd><a href=http://aryeh.name/spec/editing/editing.html>http://aryeh.name/spec/editing/editing.html</a>
<dt>Version history
<dd><a href="http://aryeh.name/gitweb.cgi?p=editing">Primary copy</a>
<dd><a href=https://github.com/ayg/editing>github mirror</a>
<dt>Issue tracker
<dd><a href="http://www.w3.org/Bugs/Public/buglist.cgi?component=HTML+Editing+APIs&bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED">All open issues</a>
<dd><a href="http://www.w3.org/Bugs/Public/enter_bug.cgi?product=WebAppsWG&component=HTML+Editing+APIs">File an issue</a>
</dl>
</div>
<h2 class=no-num id=status-of-this-document>Status of this Document</h2>
<p>This document is a preliminary draft of a specification for HTML editing
APIs, mainly defining <code><a href=#execcommand()>execCommand()</a></code> and related functions. It
largely replaces the <a href=http://www.whatwg.org/specs/web-apps/current-work/multipage/dnd.html#editing-apis>Editing
APIs</a> section of the <a href=http://www.whatwg.org/html>HTML</a>
specification. Issues that don't necessarily need discussion should preferably be
<a href="http://www.w3.org/Bugs/Public/enter_bug.cgi?product=WebAppsWG&component=HTML+Editing+APIs">filed in the issue tracker</a>,
which is generously provided by the W3C. Feedback that needs discussion should
preferably be sent to <a href=http://lists.whatwg.org/listinfo.cgi/whatwg-whatwg.org>the WHATWG list</a>,
with the string "[editing]" somewhere in the subject, CC'd to <a href=mailto:ayg@aryeh.name>ayg@aryeh.name</a> to make sure I see it. I will
handle all feedback I'm aware of, either addressing it immediately or filing a
bug if it needs longer-term consideration and is not already filed.
<p>This specification, along with the accompanying JavaScript implementation
and tests, may be used under the terms of the
<a href=http://creativecommons.org/publicdomain/zero/1.0/>CC0 1.0 Universal
License</a>. Thus anyone may reuse, modify, and redistribute them without
restriction.
<h2 class=no-num id=table-of-contents>Table of contents</h2>
<!--begin-toc-->
<ol class=toc>
<li><a class=no-num href=#status-of-this-document>Status of this Document</a></li>
<li><a class=no-num href=#table-of-contents>Table of contents</a></li>
<li><a href=#introduction>Introduction</a></li>
<li><a href=#tests>Tests</a></li>
<li><a href=#issues>Issues</a></li>
<li><a href=#commands>Commands</a>
<ol>
<li><a href=#properties-of-commands>Properties of commands</a></li>
<li><a href=#supported-commands>Supported commands</a></li>
<li><a href=#enabled-commands>Enabled commands</a></ol></li>
<li><a href=#methods-of-the-htmldocument-interface>Methods of the <code class=external data-anolis-spec=html>HTMLDocument</code> interface</a></li>
<li><a href=#common-definitions>Common definitions</a></li>
<li><a href=#common-algorithms>Common algorithms</a>
<ol>
<li><a href=#assorted-common-algorithms>Assorted common algorithms</a></li>
<li><a href=#wrapping-a-list-of-nodes>Wrapping a list of nodes</a></li>
<li><a href=#allowed-children>Allowed children</a></ol></li>
<li><a href=#inline-formatting-commands>Inline formatting commands</a>
<ol>
<li><a href=#inline-formatting-command-definitions>Inline formatting command definitions</a></li>
<li><a href=#assorted-inline-formatting-command-algorithms>Assorted inline formatting command algorithms</a></li>
<li><a href="#clearing-an-element's-value">Clearing an element's value</a></li>
<li><a href=#pushing-down-values>Pushing down values</a></li>
<li><a href=#forcing-the-value-of-a-node>Forcing the value of a node</a></li>
<li><a href="#setting-the-selection's-value">Setting the selection's value</a></li>
<li><a href=#the-backcolor-command>The <code title="">backColor</code> command</a></li>
<li><a href=#the-bold-command>The <code title="">bold</code> command</a></li>
<li><a href=#the-createlink-command>The <code title="">createLink</code> command</a></li>
<li><a href=#the-fontname-command>The <code title="">fontName</code> command</a></li>
<li><a href=#the-fontsize-command>The <code title="">fontSize</code> command</a></li>
<li><a href=#the-forecolor-command>The <code title="">foreColor</code> command</a></li>
<li><a href=#the-hilitecolor-command>The <code title="">hiliteColor</code> command</a></li>
<li><a href=#the-italic-command>The <code title="">italic</code> command</a></li>
<li><a href=#the-removeformat-command>The <code title="">removeFormat</code> command</a></li>
<li><a href=#the-strikethrough-command>The <code title="">strikethrough</code> command</a></li>
<li><a href=#the-subscript-command>The <code title="">subscript</code> command</a></li>
<li><a href=#the-superscript-command>The <code title="">superscript</code> command</a></li>
<li><a href=#the-underline-command>The <code title="">underline</code> command</a></li>
<li><a href=#the-unlink-command>The <code title="">unlink</code> command</a></ol></li>
<li><a href=#block-formatting-commands>Block formatting commands</a>
<ol>
<li><a href=#block-formatting-command-definitions>Block formatting command definitions</a></li>
<li><a href=#assorted-block-formatting-command-algorithms>Assorted block formatting command algorithms</a></li>
<li><a href=#block-extending-a-range>Block-extending a range</a></li>
<li><a href=#recording-and-restoring-overrides>Recording and restoring overrides</a></li>
<li><a href=#deleting-the-contents-of-a-range>Deleting the contents of a range</a></li>
<li><a href="#splitting-a-node-list's-parent">Splitting a node list's parent</a></li>
<li><a href=#canonical-space-sequences>Canonical space sequences</a></li>
<li><a href=#indenting-and-outdenting>Indenting and outdenting</a></li>
<li><a href=#toggling-lists>Toggling lists</a></li>
<li><a href=#justifying-the-selection>Justifying the selection</a></li>
<li><a href=#the-delete-command>The <code title="">delete</code> command</a></li>
<li><a href=#the-formatblock-command>The <code title="">formatBlock</code> command</a></li>
<li><a href=#the-forwarddelete-command>The <code title="">forwardDelete</code> command</a></li>
<li><a href=#the-indent-command>The <code title="">indent</code> command</a></li>
<li><a href=#the-inserthorizontalrule-command>The <code title="">insertHorizontalRule</code> command</a></li>
<li><a href=#the-inserthtml-command>The <code title="">insertHTML</code> command</a></li>
<li><a href=#the-insertimage-command>The <code title="">insertImage</code> command</a></li>
<li><a href=#the-insertlinebreak-command>The <code title="">insertLineBreak</code> command</a></li>
<li><a href=#the-insertorderedlist-command>The <code title="">insertOrderedList</code> command</a></li>
<li><a href=#the-insertparagraph-command>The <code title="">insertParagraph</code> command</a></li>
<li><a href=#the-inserttext-command>The <code title="">insertText</code> command</a></li>
<li><a href=#the-insertunorderedlist-command>The <code title="">insertUnorderedList</code> command</a></li>
<li><a href=#the-justifycenter-command>The <code title="">justifyCenter</code> command</a></li>
<li><a href=#the-justifyfull-command>The <code title="">justifyFull</code> command</a></li>
<li><a href=#the-justifyleft-command>The <code title="">justifyLeft</code> command</a></li>
<li><a href=#the-justifyright-command>The <code title="">justifyRight</code> command</a></li>
<li><a href=#the-outdent-command>The <code title="">outdent</code> command</a></ol></li>
<li><a href=#miscellaneous-commands>Miscellaneous commands</a>
<ol>
<li><a href=#the-copy-command>The <code title="">copy</code> command</a></li>
<li><a href=#the-cut-command>The <code title="">cut</code> command</a></li>
<li><a href=#the-paste-command>The <code title="">paste</code> command</a></li>
<li><a href=#the-selectall-command>The <code title="">selectAll</code> command</a></li>
<li><a href=#the-stylewithcss-command>The <code title="">styleWithCSS</code> command</a></li>
<li><a href=#the-usecss-command>The <code title="">useCSS</code> command</a></ol></li>
<li><a href=#additional-requirements>Additional requirements</a></li>
<li><a class=no-num href=#acknowledgements>Acknowledgements</a></ol>
<!--end-toc-->
<h2 id=introduction>Introduction</h2>
<p>This specification defines commands to edit HTML documents programmatically.
The APIs specified here were originally introduced in Microsoft's Internet
Explorer, but have subsequently been copied by other browsers in a haphazard
and imprecise fashion. Although the behavior specified here does not exactly
match any browser at the time of writing, it can serve as a target to converge
to in the future.
<p>Where the reasoning behind the specification is of interest, such as when
major preexisting rendering engines are known not to match it, the reasoning is
available by clicking the "comments" button on the right (requires JavaScript).
If you have questions about why the specification says something, check the
comments first. They're sometimes longer than the specification text itself,
and commonly record what the major browsers do and other essential information.
<p>The principles I've used for writing this specification so far are:
<ul>
<li>If all browsers that implement a particular feature agree on some detail
of how it works, match them unless there's very good reason not to. When
it's not clear what behavior is best, try to follow the implementations with
the most market share. But if one browser's behavior is clearly better than
the others', go with the better behavior.
<li>If a command is issued to format some text in a particular way, we will
format the text that way no matter what. If the user clicks the "bold"
button, they don't care that the text didn't become bold because of an
external CSS rule or for any other reason, they only care that it didn't
work. The only exception (beyond where it's simply impossible, like
propagated text-decorations we can't remove) is that we don't try to override
!important rules from external stylesheets, although we also don't go out of
our way to respect them.
<li>When we're given a presentational command like "bold", don't modify
anything other than presentational markup related to that command. If an
element has non-presentational attributes like id or class, don't split it up
or remove it or anything. At most convert it to a span, if it's some type of
presentational element. ("Presentational" here really means "browsers
produce it in response to execCommand() so we need to treat it as
presentational", so it includes things like <code class=external data-anolis-spec=html title="the strong element"><a href=http://www.whatwg.org/html/#the-strong-element>strong</a></code> and <code class=external data-anolis-spec=html title="the em element"><a href=http://www.whatwg.org/html/#the-em-element>em</a></code>.) Of
course, in some cases we have to remove elements, like when merging two
blocks.
<li>Don't interfere with more markup than necessary. If the user modifies
only a small run of text, don't go around simplifying ancestors or siblings
or whatever unless it's necessary to produce simpler markup in the place that
was actually modified.
<li>But if we are already changing around something's style, convert existing
styles to the preferred format. For instance, we use <code title=""><b></code> for bold
(if the CSS styling flag is false), and convert <code title=""><strong></code> and
<code title=""><span style="font-weight: bold"></code> if we happen to be modifying
that node anyway.
<li>Try not to make the document less conforming than it originally was. If
we happen to make it more conforming, good, although we don't have to go out
of our way to do that. In some cases we do make the document less
conforming, generally because there's some clear use-case that requires it or
because it matches existing browsers behavior. (For instance, see the
styleWithCSS = false mode, and the fact that insertImage doesn't add an
alt attribute, etc.)
<li>Keep the markup as concise as possible. (I've received feedback that
this is very important to authors.) Ideally, the markup should look as
simple and neat as what a human would have produced by hand-editing. We do
complicated manipulation to pull styles down from ancestors rather than
having to use inline CSS, and make sure to tidy up any styles on elements
that we happen to be modifying anyway. Previous principles take precedence
over this one, however.
</ul>
<h2 id=tests>Tests</h2>
<p>This specification is developed in tandem with a more or less complete <a href=implementation.js>JavaScript implementation</a>, which is used for a suite
of fully automated tests plus a few separate suites of manual tests. The tests
are:
<ul>
<li><a href=autoimplementation.html>autoimplementation.html</a>: Fully
automated tests for pretty much all commands.
<li><a href=deletetest.html>deletetest.html</a>: Manual tests for <a href=#the-delete-command>the
<code title="">delete</code> command</a>.
<li><a href=forwarddeletetest.html>forwarddeletetest.html</a>: Manual tests
for <a href=#the-forwarddelete-command>the <code title="">forwardDelete</code> command</a>.
<li><a href=insertlinebreaktest.html>insertlinebreaktest.html</a>: Manual
tests for <a href=#the-insertlinebreak-command>the <code title="">insertLineBreak</code> command</a>.
<li><a href=insertparagraphtest.html>insertparagraphtest.html</a>: Manual
tests for <a href=#the-insertparagraph-command>the <code title="">insertParagraph</code> command</a>.
<li><a href=inserttexttest.html>inserttexttest.html</a>: Manual tests for
<a href=#the-inserttext-command>the <code title="">insertText</code> command</a>, with <var title="">value</var>
"a".
<li><a href=inserttext2test.html>inserttext2test.html</a>: Manual tests for
<a href=#the-inserttext-command>the <code title="">insertText</code> command</a>, with <var title="">value</var>
" ".
</ul>
<p>The automated tests run the JavaScript implementation of the specification
on a particular input, then run the browser's implementation on the same input
for comparison. The results of running automated tests are placed in a table,
with rows marked as passing or failing based on whether the browser output is
"close enough" to the spec output. Since the tests are designed for debugging
the spec rather than actually testing conformance, minor variations are allowed
to avoid having browsers fail many tests for uninteresting reasons. Passes and
fails are based only on <code><a href=#execcommand()>execCommand()</a></code> output, not <code title="">queryCommand*()</code>: the latter is sanity-checked, and colored green
or red if it's known to be right or wrong on general principle, but spec and
browser output are not compared.
<p>The tests will optionally store the specification's result for each test in
<code title="">localStorage</code>, and will raise an alert for any new test (no
stored output), any test whose spec output is different from the last run, and
any test whose spec output is otherwise clearly bad (e.g., producing a
non-serializable DOM). This is mostly useful for debugging and
regression-testing the spec itself, and is probably not interesting to anyone
other than me.
<p>There's a suite of tests for each command (~30–300 at the time of this
writing) that can be run by clicking the "Run tests" button. This can take a
while for some commands. You can also enter your own tests manually in the box
provided. The test input is a snippet of HTML, which must have a selection
marked in it. There are three ways to mark a selection's start or end:
<ol>
<li>Square brackets mark a selection inside a text node, like <code title=""><b>foo[bar]baz</b></code> for a selection whose start and end
nodes are in the text node <code title="">foobarbaz</code>, with start offset 3
and end offset 6. Do not use square brackets where there's no text node:
<code title=""><b>[]</b></code> is bad, <code title=""><b>{}</b></code>
is correct.
<li>Curly braces mark a selection inside an element, like <code title=""><b>{foobarbaz</b>}</code> for a selection whose start node is the
element <code title=""><b></code>, whose start offset is 0, whose end node is
the root of the editable region, and whose end offset is 1. Do not use curly
braces in the middle of a text node: <code title="">foo{bar}baz</code> is bad,
<code title="">foo[bar]baz</code> is correct.
<li>The <code title="">data-start</code> and <code title="">data-end</code>
attributes mark a selection inside an element if a curly brace can't be put
there in text/html. For instance, <code title=""><table><tr>{<td>foo</td>}</tr></table></code> doesn't
work because when the fragment is parsed, the curly braces end up outside the
table. Instead, you have to do <code title=""><table><tr data-start=0
data-end=1><td>foo</table></code>.
</ol>
<p>Every input must have exactly one start marker and one end marker, which
will be removed from the DOM before the test is run. You can mix and match
marker types, e.g., <code title="">[foo}</code>.
<p>When a test runs, first the code sets up a contenteditable div with the
given contents and sets the selection as requested. Then it runs
<code><a href=#querycommandindeterm()>queryCommandIndeterm()</a></code>, <code><a href=#querycommandstate()>queryCommandState()</a></code>, and
<code><a href=#querycommandvalue()>queryCommandValue()</a></code>, and their values are noted. Then it runs
<code><a href=#execcommand()>execCommand()</a></code>. Finally, it runs
<code><a href=#querycommandindeterm()>queryCommandIndeterm()</a></code>, <code><a href=#querycommandstate()>queryCommandState()</a></code>, and
<code><a href=#querycommandvalue()>queryCommandValue()</a></code> again. Then it adds the output to the table.
<p>There is one special test type that behaves differently, "multitest". This
allows running several tests in succession, which is needed at least for
testing the effect of commands' <a href=#state-override>state override</a> or <a href=#value-override>value
override</a>. The syntax is JSON, and looks like
<pre>[<var title="">HTML input</var>,
[<var title="">command name 1</var>, <var title="">command value 1</var>],
[<var title="">command name 2</var>, <var title="">command value 2</var>],
. . .]</pre>
<p>where all the variables are properly-quoted JSON strings. <code title="">queryCommand*()</code> are not run for multitests.
<p>Commands that are expected to vary significantly based on the value of the
<a href=#css-styling-flag>CSS styling flag</a> have two tables of results. The first table runs
<code title="">execCommand("styleWithCSS", false, "false")</code> before every
command, and the second runs <code title="">execCommand("styleWithCSS", false,
"true")</code> before every command. All other commands other than multitests
run <code title="">execCommand("styleWithCSS", false, "false")</code> before every
command. The extra tests are not run in IE or Opera, because they don't
implement <a href=#the-stylewithcss-command>the <code title="">styleWithCSS</code> command</a>.
<p>The manual tests are much like the automated tests, with some key
differences. They only test one command each, with one input value (if
applicable). When a test is run, everything proceeds as in the automated case,
but instead of running <code><a href=#execcommand()>execCommand()</a></code> for the browser tests, the
user is asked to hit the appropriate key (backspace, delete, enter, etc.).
Thus when running the tests for the first time, the user has to hit a key
repeatedly, perhaps a few hundred times. The browser's result is then cached
in <code title="">localStorage</code> so no manual intervention is required on
subsequent runs except for newly-added tests, but the cached entries can be
cleared if necessary.
<p>The tests have been tested and largely work in the latest versions (at the
time of this writing) of IE, Firefox, Chrome, and Opera. Since the
implementation of the spec is in JavaScript, it's vulnerable to bugs in
browsers' JavaScript implementations. I work around or warn about some of
these, but not all. The most correct results will probably be in Firefox or
Chrome: both IE and Opera have serious known bugs that corrupt spec output for
many tests. The tests are still useful for reviewing the browser output, but
spec output in those browsers should be sanity-checked and compared against
another browser's spec output in case of doubt.
<p>These tests are really meant to aid spec development by seeing how browsers
behave, not to aid browser development by seeing where the browser doesn't
match the spec. Proper conformance tests would a) record all expected results
statically to avoid browser JS bugs, and b) compare expected and actual results
much more strictly. They would also test a <em>lot</em> more corner cases,
like nested <code title="">contenteditable=false</code> regions. It should be
relatively easy to transform the existing tests into proper conformance tests,
but there's not much point until the spec is more stable.
<p>The implementation is also used for an actual <a href=editor.html>rich-text
editor</a>, but it's currently more of a toy than anything. Significant
functionality is probably broken, especially outside of Gecko/WebKit. I might
spend some more time getting it to work right, but it's certainly not going to
be very useful on real-world sites, since there's no way any of this stuff will
work in IE8.
<h2 id=issues>Issues</h2>
<p>This specification is mostly feature-complete. It's more or less fully
implemented in JavaScript, and has been tested on a fairly significant amount
of artificial input. It has not been tested on real-world sites that use
execCommand(), and has not been thoroughly reviewed by anyone other than me.
It should be considered mostly stable and awaiting implementater review and
feedback.
<p>Significant known issues that I need feedback on, or otherwise am not
planning to fix just yet:
<ul>
<li>Need to make CSS terminology more precise, about setting/unsetting CSS
properties. The intent is to modify the style attribute, CSSOM-style.
Suggestions appreciated on how I should spec this.
<li>I use <a href=http://dev.w3.org/csswg/cssom/#resolved-value>resolved value</a> instead of computed or used or anything like that, just
because that's what my test implementation uses (via getComputedStyle). This
is not necessarily the best actual choice: if it should be something else,
please tell me.
<li><p>I haven't paid much attention to performance. The algorithms here
aren't performance-critical in most cases, but I might have accidentally
included some algorithms that are too slow anyway on large pages. Generally
I haven't worried about throwing nodes away and recreating them multiple
times or things like that, as long as it produces the correct result.
<p>If it would be useful to implementers for me to spend time and spec
complexity on avoiding some of the masses of useless operations that are
currently required, please say so. All intermediate DOM states are
black-box detectable via mutation events or whatever their replacement will
be, so implementers theoretically can't optimize most of this stuff too much
themselves, but in practice I doubt anyone will rely on the intermediate DOM
states much.
<li><code class=external data-anolis-spec=html title="the br element"><a href=http://www.whatwg.org/html/#the-br-element>br</a></code>s are a nightmare. I have tons of hacks all over the place which
are totally wrong, mostly to account for the fact that sometimes <code class=external data-anolis-spec=html title="the br element"><a href=http://www.whatwg.org/html/#the-br-element>br</a></code>s do
nothing and we need to treat that case magically. I don't know what a good
way is to fix this. At this point I've mostly gotten the evil concentrated
in the definitions "collapsed line break", "extraneous line break", and
"collapsed block prop", but there's lots of other special-case handling
scattered about. Feedback appreciated. How do browsers handle this?
<li>The CSS styling flag is an issue. Currently authors are forced to turn
it entirely on or entirely off. If it's on, it produces stuff like <code title=""><span style=font-weight:bold></code> instead of <code title=""><b></code>, while if it's off, it produces stuff like <code title=""><font color=red></code> instead of <code title=""><span
style=color:red></code>. The issue is that authors might want a mix, like
making the markup as concise as possible while still conforming, and they
can't do that. Changing the flag on a per-command basis doesn't help because
of things like the "restore the values" algorithm, which might create several
different types of style at once and has to use the same styling flag for all
of them. This was discussed back in March in <a href=http://lists.whatwg.org/htdig.cgi/whatwg-whatwg.org/2011-March/030714.html>this
thread</a>, along with a number of other things, but at that time I hadn't
written commands that change multiple styles at once, so it seemed feasible
to ask authors to switch styleWithCSS on or off on a per-command basis.
<li>I haven't defined the "undo" or "redo" commands yet. They look very
complicated to define precisely, and other people are working on them right
now.
</ul>
<p class=XXX>A variety of other issues are also noted in the text, formatted
like this. Feedback would be appreciated on all of them.
<div class=comments>
<p>TODO:
<ul>
<li>Scour browser bug trackers to try spotting issues I haven't thought of.
<li>The wording I use for DOM stuff is not maximally precise. Really I want
DOM Core to define nice concepts that I can xref, like "insert a node". I
don't want to have to explicitly refer to DOM methods like insertBefore()
every time I want to move things.
<li>JavaScript can modify the DOM synchronously in some cases, such as DOM
mutation events and onunload when moving around iframes and objects. This
has to be dealt with somehow. (Pointed out by Ryosuke Niwa of WebKit:
<a href=http://lists.whatwg.org/pipermail/whatwg-whatwg.org/2011-March/030730.html>1</a>
<a href=http://lists.whatwg.org/pipermail/whatwg-whatwg.org/2011-March/030751.html>2</a>)
<li>What happens if you do something like delete a selection or insert text or
whatnot in the middle of a surrogate pair? This could make the content not
serialize through a character encoding change.
<li>Probably need to record and restore overrides in some more places.
<li>Some more thought needs to go into what happens to the selection when you
mutate the DOM. In some cases the results are pretty arbitrary. It might
make sense to do some kind of normalization.
<li>I'm sloppy about handling things like nodes that don't descend from a
Document, comments that are children of a Document, that sort of thing. Not
essential for prototyping, but needs to be cleaned up eventually. Mostly we
should be able to avoid the problems by requiring that everything be
editable, since that immediately means it has to descend from an element or
Document (and cannot be parentless itself).
<li>I need to pay more attention to invisible nodes. These will have no visual
effect, but they'll make many algorithms behave differently: decomposing a
range, block-extending, etc. Also, need to improve the definition to include
things like whitespace-only nodes.
<li>Have to make sure that in all the places where we set a selection, it's
valid.
<li>Redefine things in terms of ranges, not selections.
<li>Allow some type of switch to affect non-editable regions too, perhaps on a
per-command basis.
<li>Things like delete, forwardDelete, insertText need to handle non-BMP
characters.
</ul>
<p>Also TODO: Things that are only implemented by a couple of browsers and may
or may not be useful to spec:
<ul>
<li>decreaseFontSize, increaseFontSize: Only implemented in Gecko and Opera.
<li>contentReadOnly, enableInlineTableEditing, enableObjectResizing, heading,
insertBrOnReturn: MDC docs say not implemented in IE (didn't test).
<li>readOnly: MDC docs say it's a deprecated equivalent of contentReadOnly,
so presumably like useCSS but less popular.
<li>2D-Position, absolutePosition, clearAuthenticationCache, createBookmark,
insertButton, insertFieldset, insertIframe, insertInput*, insertMarquee,
insertSelectDropdown, insertSelectListbox, insertTextarea, liveResize,
multipleSelection, overwrite, print, refresh, saveAs, unbookmark: Mentioned
in MSDN docs but not MDC, so presumably IE-only. Some of these seem
inappropriate or useless, others will bear investigation.
<li>findString, fontSizeDelta, insertNewlineInQuotedContent, justifyNone,
print, transpose: There's code for these in WebKit,
Source/WebCore/editing/EditorCommand.cpp, but I didn't see them mentioned
elsewhere. Some might be worth adding.
<li>unselect: Seems to not be implemented by Gecko or Opera, and IE behaves
oddly: it seems to collapse the selection instead of removing it. Will only
implement if there seems to be demand; it's redundant to
Selection.removeAllRanges() anyway.
</ul>
<p>Things I haven't looked at that multiple browsers implement:
<ul>
<li>redo, undo: Needs review of the Google work on this; will probably be
quite complicated.
</ul>
<p>Also need to look at contenteditable=plaintext-only.
</div>
<p>Things that would be useful to address for the future but aren't important
to fix right now are in comments prefixed with "TODO".
<h2 id=commands>Commands</h2>
<h3 id=properties-of-commands>Properties of commands</h3>
<p>This specification defines a number of <dfn id=command title=command>commands</dfn>,
identified by <a class=external data-anolis-spec=domcore href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#ascii-case-insensitive>ASCII case-insensitive</a>
strings. Each <a href=#command>command</a> can have several pieces of data associated
with it:
<ul>
<li><dfn id=action>Action</dfn>: What the <a href=#command>command</a> does when executed via
<code><a href=#execcommand()>execCommand()</a></code>. Every <a href=#command>command</a> defined in this
specification has an <a href=#action>action</a> defined for it in the relevant
section. For example, <a href=#the-bold-command>the <code title="">bold</code> command</a>'s
<a href=#action>action</a> generally makes the current selection bold, or removes
bold if the selection is already bold. An editing toolbar might provide
buttons that execute the <a href=#action>action</a> for a <a href=#command>command</a> if
clicked, or a script might run an <a href=#action>action</a> without user
interaction to achieve some particular effect.
<li><dfn id=indeterminate>Indeterminate</dfn>: A boolean value returned by
<code><a href=#querycommandindeterm()>queryCommandIndeterm()</a></code>, depending on the current state of the
document. Generally, a <a href=#command>command</a> that has a <a href=#state>state</a>
defined will be <a href=#indeterminate>indeterminate</a> if the <a href=#state>state</a> is true
for part but not all of the current selection, and a <a href=#command>command</a>
that has a <a href=#value>value</a> defined will be <a href=#indeterminate>indeterminate</a> if
different parts of the selection have different <a href=#value title=value>values</a>. An editing toolbar might display a button or
control in a special way if the <a href=#command>command</a> is
<a href=#indeterminate>indeterminate</a>, like showing a "bold" button as partially
depressed, or leaving a font size selector blank instead of showing the font
size of the current selection. As a rule, a <a href=#command>command</a> can only be
<a href=#indeterminate>indeterminate</a> if its <a href=#state>state</a> is false, supposing it
has a <a href=#state>state</a>.
<li><dfn id=state>State</dfn>: A boolean value returned by
<code><a href=#querycommandstate()>queryCommandState()</a></code>, depending on the current state of the
document. The <a href=#state>state</a> of a <a href=#command>command</a> is true if it is
already in effect, in some sense specific to the <a href=#command>command</a>. Most
<a href=#command title=command>commands</a> that have a <a href=#state>state</a> defined
will take opposite <a href=#action title=action>actions</a> depending on whether the
<a href=#state>state</a> is true or false, such as making the selection bold if the
<a href=#state>state</a> is false and removing bold if the <a href=#state>state</a> is
true. Others will just have no effect if the <a href=#state>state</a> is true,
like <a href=#the-justifycenter-command>the <code title="">justifyCenter</code> command</a>. Still others
will have the same effect regardless, like <a href=#the-stylewithcss-command>the <code title="">styleWithCss</code> command</a>. An editing toolbar might display a
button or control differently depending on the <a href=#state>state</a> and <a href=#indeterminate title=indeterminate>indeterminacy</a> of the <a href=#command>command</a>.
<li><dfn id=value>Value</dfn>: A string returned by <code><a href=#querycommandvalue()>queryCommandValue()</a></code>,
depending on the current state of the document. A <a href=#command>command</a>
usually has a <a href=#value>value</a> instead of a <a href=#state>state</a> if the
property it modifies can take more than two different values, like <a href=#the-forecolor-command>the
<code title="">foreColor</code> command</a>. If the <a href=#command>command</a> is
<a href=#indeterminate>indeterminate</a>, its <a href=#value>value</a> is generally based on the
start of the selection. Otherwise, in most cases the <a href=#value>value</a>
holds true for the entire selection, but see <a href=#the-justifycenter-command>the <code title="">justifyCenter</code> command</a> and <a href=#the-justifyfull-command title="the justifyFull
command">its</a> <a href=#the-justifyleft-command title="the justifyLeft command">three</a> <a href=#the-justifyright-command title="the justifyRight command">companions</a> for an exception. An
editing toolbar might display the <a href=#value>value</a> of a
<a href=#command>command</a> as selected in a drop-down or filled in in a text box,
if the <a href=#command>command</a> isn't <a href=#indeterminate>indeterminate</a>.
<li><dfn id=relevant-css-property>Relevant CSS property</dfn>: This is defined for certain <a href=#inline-formatting-commands>inline formatting commands</a>, and is used
in algorithms specific to those commands. It is an implementation detail,
and is not exposed to authors. If a <a href=#command>command</a> does not have a
<a href=#relevant-css-property>relevant CSS property</a> specified, it defaults to null.
</ul>
<h3 id=supported-commands>Supported commands</h3>
<p class=comments>If you try doing anything with an unrecognized command, IE9
throws an "Invalid argument" exception, and Firefox 6.0a2 throws
NS_ERROR_NOT_IMPLEMENTED. Chrome 14 dev and Opera 11.11 both just return a
useless value. I go with IE/Gecko, although of course with a standard
exception type.
<p>Some <a href=#command title=command>commands</a> will be <dfn id=supported>supported</dfn> in a
given user agent, and some will not. All <a href=#command title=command>commands</a>
defined in this specification must be <a href=#supported>supported</a>, except optionally
<a href=#the-copy-command>the <code title="">copy</code> command</a>, <a href=#the-cut-command>the <code title="">cut</code> command</a>, and/or <a href=#the-paste-command>the <code title="">paste</code>
command</a>. Additional <a href=#command title=command>commands</a> can also be
<a href=#supported>supported</a>, but implementers should prefix any nonstandard
<a href=#command>command</a> names with a vendor-specific string (e.g., "ms", "moz",
"webkit", "opera").
<p class=comments>I.e., no trying to look good on lazy conformance tests by
just sticking in a stub implementation that does nothing.
<p>A <a href=#command>command</a> that does absolutely nothing in a particular user
agent, such that <code><a href=#execcommand()>execCommand()</a></code> never has any effect and
<code><a href=#querycommandenabled()>queryCommandEnabled()</a></code> and <code><a href=#querycommandindeterm()>queryCommandIndeterm()</a></code> and
<code><a href=#querycommandstate()>queryCommandState()</a></code> and <code><a href=#querycommandvalue()>queryCommandValue()</a></code> each
return the same value all the time, must not be <a href=#supported>supported</a>.
<p>In a particular user agent, every <a href=#command>command</a> must be consistently
either <a href=#supported>supported</a> or not. Specifically, a user agent must not
permit one page to see the same <a href=#command>command</a> sometimes
<a href=#supported>supported</a> and sometimes not over the course of the same browsing
session, unless the user agent has been upgraded or reconfigured in the middle
of a session. However, user agents may treat the same <a href=#command>command</a> as
<a href=#supported>supported</a> for some pages and not others, e.g., if the
<a href=#command>command</a> is only supported for certain origins for security
reasons.
<p>Authors can tell whether a <a href=#command>command</a> is <a href=#supported>supported</a>
using <code><a href=#querycommandsupported()>queryCommandSupported()</a></code>.
<h3 id=enabled-commands>Enabled commands</h3>
<p>At any given time, a <a href=#supported>supported</a> command can be either
<dfn id=enabled>enabled</dfn> or not. Authors can tell whether a <a href=#command>command</a> is
currently <a href=#enabled>enabled</a> using <code><a href=#querycommandenabled()>queryCommandEnabled()</a></code>. <a href=#command title=command>Commands</a> that are not <a href=#enabled>enabled</a> do nothing, as
described in the definitions of the various methods that invoke <a href=#command title=command>commands</a>.
<div class=comments>
<p>Testing with bold:
<p>IE10PP2 seems to return true if the active range's start node is editable,
false otherwise.
<p>Firefox 6.0a2 seems to always return true if there's anything editable on the
page, and throw otherwise. (This is <a href="https://bugzilla.mozilla.org/show_bug.cgi?id=676401">bug 676401</a>.)
<p>Chrome 14 dev seems to behave the same as IE10PP2.
<p>Opera 11.11 seems to always return true if there's anything editable on the
page, and false otherwise.
<p>Firefox and Opera behave more or less uselessly. IE doesn't make much sense,
in that whether a command is enabled seems meaningless: it will execute it on
all nodes in the selection, editable or not. Chrome's definition makes sense
in that it will only run the command if it's enabled, but it doesn't make much
sense to only have the command run if the start is editable.
<p>It's not clear to me what the point of this method is. There's no way we're
going to always return true if the command will do something and false if it
won't. I just stuck with a really conservative definition that happens to be
convenient: if there's nothing selected, obviously nothing will work, and we
want to bail out early in that case anyway because all the algorithms will talk
about the active range. If there are use-cases for it to be more precise, I
could make it so.
</div>
<p>Among <a href=#command title=command>commands</a> defined in this specification,
those listed in <a href=#miscellaneous-commands>Miscellaneous commands</a> are
always <a href=#enabled>enabled</a>. The other <a href=#command title=command>commands</a>
defined here are <a href=#enabled>enabled</a> if the <a href=#active-range>active range</a> is not
null, and disabled otherwise.
<h2 id=methods-of-the-htmldocument-interface>Methods of the <code class=external data-anolis-spec=html><a href=http://www.whatwg.org/html/#htmldocument>HTMLDocument</a></code> interface</h2>
<p class=comments>TODO: Define behavior for <var title="">show UI</var>.
<p>When the <dfn id=execcommand() title=execCommand()><code>execCommand(<var title="">command</var>,
<var title="">show UI</var>, <var title="">value</var>)</code></dfn> method on the <code class=external data-anolis-spec=html><a href=http://www.whatwg.org/html/#htmldocument>HTMLDocument</a></code> interface is invoked, the user agent
must run the following steps:
<ol>
<li>If only one argument was provided, let <var title="">show UI</var> be false.
<li>If only one or two arguments were provided, let <var title="">value</var> be the
empty string.
<li>If <var title="">command</var> is not <a href=#supported>supported</a>, raise a
<code class=external data-anolis-spec=domcore title=dom-DOMException-NOT_SUPPORTED_ERR><a href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#dom-domexception-not_supported_err>NOT_SUPPORTED_ERR</a></code> exception.
<li>
<p class=comments>I'm just speccing INVALID_ACCESS_ERR for consistency. I
don't expect real-world commands are likely to not have an action defined,
but you never know.
<p>If <var title="">command</var> has no <a href=#action>action</a>, raise an
<code class=external data-anolis-spec=domcore title=dom-DOMException-INVALID_ACCESS_ERR><a href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#dom-domexception-invalid_access_err>INVALID_ACCESS_ERR</a></code> exception.
<p class=note>No such <a href=#command>command</a> is defined in this specification.
<li>
<p class=comments>I didn't research this closely, but at a first glance, this
is possibly how Chrome 14 dev and Opera 11.11 behave. Maybe also Firefox
6.0a2, except it throws if the command isn't enabled, I think. IE9 returns
true in at least some cases even if the command is disabled. TODO: Is this
right? Maybe we should be returning false in other cases too?
<p>If <var title="">command</var> is not <a href=#enabled>enabled</a>, return false.
<li>Take the <a href=#action>action</a> for <var title="">command</var>, passing
<var title="">value</var> to the instructions as an argument.
<li>Return true.
</ol>
<p>When the <dfn id=querycommandenabled() title=queryCommandEnabled()><code>queryCommandEnabled(<var title="">command</var>)</code></dfn>
method on the <code class=external data-anolis-spec=html><a href=http://www.whatwg.org/html/#htmldocument>HTMLDocument</a></code> interface is
invoked, the user agent must run the following steps:
<ol>
<li>If <var title="">command</var> is not <a href=#supported>supported</a>, raise a
<code class=external data-anolis-spec=domcore title=dom-DOMException-NOT_SUPPORTED_ERR><a href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#dom-domexception-not_supported_err>NOT_SUPPORTED_ERR</a></code> exception.
<li>Return true if <var title="">command</var> is <a href=#enabled>enabled</a>, false
otherwise.
</ol>
<div class=comments>
<p>What happens if you call queryCommand(Indeterm|State|Value)() on a command
where it makes no sense?
<p>IE9 consistently returns false for all three.
<p>Firefox 6.0a2 consistently throws NS_ERROR_FAILURE for indeterm/state if not
supported, and returns an empty string for value. Exceptions include unlink
(seems to always return indeterm/state false), and styleWithCss/useCss (throw
NS_ERROR_FAILURE even for value).
<p>Chrome 14 dev returns false for all three, and even does this for unrecognized
commands. It also always defines value if state is defined: it returns the
state cast to a string, either "true" or "false".
<p>Opera 11.11 returns false for state and "" for value (it doesn't support
indeterm). Like Chrome, this is even for unrecognized commands.
<p>Gecko's behavior is the most useful. If the author tries querying some aspect
of a command that makes no sense, they shouldn't receive a value that looks
like it might make sense but is actually just a constant. However, I go even
further than Gecko: I require exceptions even for value, since doing otherwise
makes no sense.
</div>
<p>When the <dfn id=querycommandindeterm() title=queryCommandIndeterm()><code>queryCommandIndeterm(<var title="">command</var>)</code></dfn>
method on the <code class=external data-anolis-spec=html><a href=http://www.whatwg.org/html/#htmldocument>HTMLDocument</a></code> interface is
invoked, the user agent must run the following steps:
<ol>
<li>If <var title="">command</var> is not <a href=#supported>supported</a>, raise a
<code class=external data-anolis-spec=domcore title=dom-DOMException-NOT_SUPPORTED_ERR><a href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#dom-domexception-not_supported_err>NOT_SUPPORTED_ERR</a></code> exception.
<li>If <var title="">command</var> has no <a href=#indeterminate title=indeterminate>indeterminacy</a>, raise an <code class=external data-anolis-spec=domcore title=dom-DOMException-INVALID_ACCESS_ERR><a href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#dom-domexception-invalid_access_err>INVALID_ACCESS_ERR</a></code>
exception.
<li>If <var title="">command</var> is not <a href=#enabled>enabled</a>, return false.
<li>Return true if <var title="">command</var> is <a href=#indeterminate>indeterminate</a>,
otherwise false.
</ol>
<p>When the <dfn id=querycommandstate() title=queryCommandState()><code>queryCommandState(<var title="">command</var>)</code></dfn>
method on the <code class=external data-anolis-spec=html><a href=http://www.whatwg.org/html/#htmldocument>HTMLDocument</a></code> interface is
invoked, the user agent must run the following steps:
<ol>
<li>If <var title="">command</var> is not <a href=#supported>supported</a>, raise a
<code class=external data-anolis-spec=domcore title=dom-DOMException-NOT_SUPPORTED_ERR><a href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#dom-domexception-not_supported_err>NOT_SUPPORTED_ERR</a></code> exception.
<li>If <var title="">command</var> has no <a href=#state>state</a>, raise an
<code class=external data-anolis-spec=domcore title=dom-DOMException-INVALID_ACCESS_ERR><a href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#dom-domexception-invalid_access_err>INVALID_ACCESS_ERR</a></code> exception.
<li>If <var title="">command</var> is not <a href=#enabled>enabled</a>, return false.
<li>If the <a href=#state-override>state override</a> for <var title="">command</var> is set, return
it.
<li>Return true if <var title="">command</var>'s <a href=#state>state</a> is true, otherwise
false.
</ol>
<p class=comments>Firefox 6.0a2 always throws an exception when this is
called. Opera 11.11 seems to return false if there's nothing editable on the
page, which is unhelpful. The spec follows IE9 and Chrome 14 dev. The reason
this is useful, compared to just running one of the other methods and seeing if
you get a NOT_SUPPORTED_ERR, is that other methods might throw different
exceptions for other reasons. It's easier to check a boolean than to check
exception types, especially since as of June 2011 UAs aren't remotely
consistent on what they do with unsupported commands.
<p>When the <dfn id=querycommandsupported() title=queryCommandSupported()><code>queryCommandSupported(<var title="">command</var>)</code></dfn>
method on the <code class=external data-anolis-spec=html><a href=http://www.whatwg.org/html/#htmldocument>HTMLDocument</a></code> interface is
invoked, the user agent must return true if <var title="">command</var> is
<a href=#supported>supported</a>, and false otherwise.
<p>When the <dfn id=querycommandvalue() title=queryCommandValue()><code>queryCommandValue(<var title="">command</var>)</code></dfn>
method on the <code class=external data-anolis-spec=html><a href=http://www.whatwg.org/html/#htmldocument>HTMLDocument</a></code> interface is
invoked, the user agent must run the following steps:
<ol>
<li>If <var title="">command</var> is not <a href=#supported>supported</a>, raise a
<code class=external data-anolis-spec=domcore title=dom-DOMException-NOT_SUPPORTED_ERR><a href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#dom-domexception-not_supported_err>NOT_SUPPORTED_ERR</a></code> exception.
<li>If <var title="">command</var> has no <a href=#value>value</a>, raise an
<code class=external data-anolis-spec=domcore title=dom-DOMException-INVALID_ACCESS_ERR><a href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#dom-domexception-invalid_access_err>INVALID_ACCESS_ERR</a></code> exception.
<li>
<p class=comments>This is what Firefox 6.0a2 and Opera 11.11 seem to do. Chrome 14 dev
seems to return the string "false", and IE9 seems to return boolean false.
<p>If <var title="">command</var> is not <a href=#enabled>enabled</a>, return the empty
string.
<li>
<p class=comments>Yuck. This is incredibly messy, as are lots of other
fontSize-related things, but I don't want to define a whole second notion of
value for the sake of a single command . . .
<p>If <var title="">command</var> is "fontSize" and its <a href=#value-override>value override</a>
is set, convert the <a href=#value-override>value override</a> to an integer number of
pixels and return the <a href=#legacy-font-size-for>legacy font size for</a> the result.
<li>If the <a href=#value-override>value override</a> for <var title="">command</var> is set, return
it.
<li>Return <var title="">command</var>'s <a href=#value>value</a>.
</ol>
<p>All of these methods must treat their <var title="">command</var> argument <a class=external data-anolis-spec=domcore href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#ascii-case-insensitive title="ASCII case-insensitive">ASCII
case-insensitively</a>.
<div class=note>
<p>The methods in this section have mostly been designed so that the following
invariants hold after <code title="">execCommand()</code> is called, assuming it
didn't throw an exception:
<ul>
<li><code title="">queryCommandIndeterm()</code> will return false (or throw an
exception).
<li><code title="">queryCommandState()</code> will return the opposite of what it did
before <code title="">execCommand()</code> was called (or throw an exception).
<li><code title="">queryCommandValue()</code> will return something equivalent to the
value passed to <code title="">execCommand()</code> (or throw an exception).
"Equivalent" here needs to be construed broadly in some cases, such as
<code title="">fontSize</code>.
</ul>
<p>The first two points do not always hold for <code title="">strikethrough</code>
or <code title="">underline</code>, because it can be impossible to unset
text-decoration in CSS. Also, by design, the state of <code title="">insertOrderedList</code> and <code title="">insertUnorderedList</code> might
be true both before and after calling, because they only remove one level of
indentation. <code title="">unlink</code> should set the value to null. And
finally, the state of the various <code title="">justify</code> commands should
always be true after calling, and the value should always be the appropriate
string ("center", "justify", "left", or "right"). Any other deviations from
these invariants are bugs in the specification.
</div>
<h2 id=common-definitions>Common definitions</h2>
<p>An <dfn id=html-element>HTML element</dfn> is an <code class=external data-anolis-spec=domcore><a href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#element>Element</a></code> whose <a class=external data-anolis-spec=domcore href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#concept-element-namespace title=concept-element-namespace>namespace</a> is the
<a class=external data-anolis-spec=domcore href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#html-namespace>HTML namespace</a>.
<p>A <dfn id=prohibited-paragraph-child-name>prohibited paragraph child name</dfn> is "address", "article",
"aside", "blockquote", "caption", "center", "col", "colgroup", "dd", "details",
"dir", "div", "dl", "dt", "fieldset", "figcaption", "figure", "footer", "form",
"h1", "h2", "h3", "h4", "h5", "h6", "header", "hgroup", "hr", "li", "listing",
"menu", "nav", "ol", "p", "plaintext", "pre", "section", "summary", "table",
"tbody", "td", "tfoot", "th", "thead", "tr", "ul", or "xmp".
<p class=comments>These are all the things that will close a <p> if found as
a descendant. I think. Plus table stuff, since that can't be a descendant of
a p either, although it won't auto-close it.
<p>A <dfn id=prohibited-paragraph-child>prohibited paragraph child</dfn> is an <a href=#html-element>HTML element</a>
whose <a class=external data-anolis-spec=domcore href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#concept-element-local-name title=concept-element-local-name>local name</a> is a <a href=#prohibited-paragraph-child-name>prohibited paragraph child name</a>.
<p class=comments>The block/inline node definitions are CSS-based. "Prohibited
paragraph child" is conceptually similar to "block node", but based on the
element name. Generally we want to use block/inline node when we're interested
in the visual effect, and prohibited paragraph children when we're concerned
about parsing or semantics. TODO: Audit all "block node" usages to see if they
need to become "visible block node", now that block nodes can be invisible (if
they descend from display: none).
<p>A <dfn id=block-node>block node</dfn> is either an <code class=external data-anolis-spec=domcore><a href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#element>Element</a></code> whose "display" property
does not have <a href=http://dev.w3.org/csswg/cssom/#resolved-value>resolved value</a> "inline" or "inline-block" or "inline-table" or
"none", or a <code class=external data-anolis-spec=domcore><a href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#document>Document</a></code>, or a <code class=external data-anolis-spec=domcore><a href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#documentfragment>DocumentFragment</a></code>.
<p>An <dfn id=inline-node>inline node</dfn> is a <a class=external data-anolis-spec=domcore href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#concept-node title=concept-node>node</a> that is not a <a href=#block-node>block
node</a>.
<p>An <dfn id=editing-host>editing host</dfn> is a <a class=external data-anolis-spec=domcore href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#concept-node title=concept-node>node</a> that is either an <code class=external data-anolis-spec=domcore><a href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#element>Element</a></code> with
a <code class=external data-anolis-spec=html title=attr-contenteditable><a href=http://www.whatwg.org/html/#attr-contenteditable>contenteditable</a></code>
attribute set to the true state, or the <code class=external data-anolis-spec=domcore><a href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#element>Element</a></code> <a class=external data-anolis-spec=domcore href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#concept-tree-child title=concept-tree-child>child</a> of a <code class=external data-anolis-spec=domcore><a href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#document>Document</a></code>
whose <code class=external data-anolis-spec=html><a href=http://www.whatwg.org/html/#designmode>designMode</a></code> is enabled.
<p>Something is <dfn id=editable>editable</dfn> if it is a <a class=external data-anolis-spec=domcore href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#concept-node title=concept-node>node</a> which is not an
<a href=#editing-host>editing host</a>, does not have a <code class=external data-anolis-spec=html title=attr-contenteditable><a href=http://www.whatwg.org/html/#attr-contenteditable>contenteditable</a></code> attribute set to the false
state, and whose <a class=external data-anolis-spec=domcore href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#concept-tree-parent title=concept-tree-parent>parent</a> is an <a href=#editing-host>editing host</a> or
<a href=#editable>editable</a>.
<p class=note>An <a href=#editable>editable</a> node cannot be a <code class=external data-anolis-spec=domcore><a href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#document>Document</a></code> or
<code class=external data-anolis-spec=domcore><a href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#documentfragment>DocumentFragment</a></code>, its <a class=external data-anolis-spec=domcore href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#concept-tree-parent title=concept-tree-parent>parent</a> cannot be null, and it must descend from
either an <code class=external data-anolis-spec=domcore><a href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#element>Element</a></code> or a <code class=external data-anolis-spec=domcore><a href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#document>Document</a></code>.
<p>The <dfn id=editing-host-of>editing host of</dfn> <var title="">node</var> is null if <var title="">node</var> is
neither <a href=#editable>editable</a> nor an <a href=#editing-host>editing host</a>; <var title="">node</var>
itself, if <var title="">node</var> is an <a href=#editing-host>editing host</a>; or the nearest
<a class=external data-anolis-spec=domcore href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#concept-tree-ancestor title=concept-tree-ancestor>ancestor</a> of <var title="">node</var> that is an <a href=#editing-host>editing host</a>, if
<var title="">node</var> is <a href=#editable>editable</a>.
<p>Two <a class=external data-anolis-spec=domcore href=http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#concept-node title=concept-node>nodes</a> are <dfn id=in-the-same-editing-host>in the same editing host</dfn> if the <a href=#editing-host-of>editing
host of</a> the first is non-null and the same as the <a href=#editing-host-of>editing host
of</a> the second.
<p class=note>Barring bugs, the algorithms here will not alter the attributes
of a non-editable element; will not remove a non-editable node from its parent
(except to immediately give it a new parent in the same editing host); and will
not add, remove, or reorder children of a node unless it is either editable or
an editing host. An editing host is never editable, so authors are assured
that editing commands will only modify the editing host's contents and not the
editing host itself.
<p>A <dfn id=collapsed-line-break>collapsed line break</dfn> is a <code class=external data-anolis-spec=html title="the br element"><a href=http://www.whatwg.org/html/#the-br-element>br</a></code> that begins a line box which
has nothing else in it, and therefore has zero height.
<p class=XXX>Is this a good definition at all? I mean things like
<p>foo<br></p>, or the second one in <p>foo<br><br></p>.
The way I test it is by adding a text node after it containing a zwsp; if that
changes the offsetHeight of its nearest non-inline ancestor, I deem it
collapsed. But what if it happens to be display: none right now, for instance?
Or its ancestor has a fixed height? Would it be better to use some DOM-based
definition?
<p class=comments>TODO: The thing about li is a not very nice hack. The issue
is that an li won't collapse even if it has no children at all, but that's not