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Break up section 6 a bit more to make it more readable. (#398)
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* Break up section 6 a bit more to make it more readable.

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silviapfeiffer authored Dec 4, 2017
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Expand Up @@ -4068,13 +4068,8 @@ manner suiting the user.</p>

<li><p>Let |left| be ''|offset|&#x2009;%''. [[!CSS-VALUES]]</p></li>

<li>
<p>Apply the terms of the CSS specifications to |nodes| with the same constraints that are
used when they are applied to |nodes| of a |cue| that is not part of a region.</p>

<p>Let |boxes| be the boxes generated as descendants of the initial containing block, along
with their positions.</p>
</li>
<li><p><a>Obtain a set of CSS boxes</a> |boxes| positioned relative to an initial containing
block.</p></li>

<li><p>If there are no line boxes in |boxes|, skip the remainder of these substeps for |cue|.
The cue is ignored.</p></li>
Expand All @@ -4100,9 +4095,12 @@ manner suiting the user.</p>
dragging them to another location on the <a element>video</a>, or even off the <a element>video</a>
entirely.</p>

<p>When the algorithm above requires that the user agent <dfn>apply WebVTT cue settings</dfn> to
obtain CSS boxes from a <a>list of WebVTT Node Objects</a> |nodes|, the user agent must run the
following algorithm.</p>

<h3 id=processing-cue-settings algorithm>Processing cue settings</h3>

<p>When the processing algorithm above requires that the user agent <dfn>apply WebVTT cue
settings</dfn> to obtain CSS boxes from a <a>list of WebVTT Node Objects</a> |nodes|, the user agent
must run the following algorithm.</p>

<ol algorithm="apply WebVTT cue settings">

Expand Down Expand Up @@ -4328,112 +4326,8 @@ following algorithm.</p>
CSS values used by the next section to set CSS properties for the rendering; ''vw'' and ''vh'' are
CSS units.) [[!CSS-VALUES]]</p></li>

<li>

<p>Apply the terms of the CSS specifications to |nodes| within the following constraints, thus
obtaining a set of CSS boxes positioned relative to an initial containing block: [[!CSS22]]</p>

<ul>

<li><p>The <i>document tree</i> is the tree of <a lt="WebVTT Node Object">WebVTT Node Objects</a>
rooted at |nodes|.</p></li>

<li>
<p>For the purpose of selectors in STYLE blocks of a WebVTT file, the style sheet must apply to
a hypothetical document that contains a single empty element with no explicit name, no
namespace, no attributes, no classes, no IDs, and unknown primary language, that acts like the
<a>media element</a> for the <a>text tracks</a> that were sourced from the given WebVTT file.
The selectors must not match other <a>text tracks</a> for the same <a>media element</a>. In this
hypothetical document, the element must not match any selector that would match the element
itself.</p>

<p class=note>This element exists only to be the <a spec=selectors>originating element</a> for
the ''::cue'', ''::cue()'', ''::cue-region'' and ''::cue-region()'' pseudo-elements.</p>
</li>

<li>
<p>For the purpose of determining the <a spec=css-cascade>cascade</a> of the declarations in
STYLE blocks of a WebVTT file, the relative order of appearance of the style sheets must be the
same order as they were added to the collection, and the order of appearance of the collection
must be after any style sheets that apply to the associated <a element>video</a> element's
document.</p>

<div class=example>
<p>For example, given the following (invalid) HTML document:</p>

<pre>
&lt;!doctype html>
&lt;title>Invalid cascade example&lt;/title>
&lt;video controls autoplay src="video.webm">
&lt;track default src="track.vtt">
&lt;/video>
&lt;style>
::cue { color:red }
&lt;/style>
</pre>

<p>...and the "track.vtt" file contains:</p>

<pre>
WEBVTT

STYLE
::cue { color:lime }

00:00:00.000 --> 00:00:25.000
Red or green?
</pre>

<p>The ''color:lime'' declaration would win, because it is last in the <a
spec=css-cascade>cascade</a>, even though the <a element>style</a> element is after the <a
element>video</a> element in the document order.</p>
</div>
</li>

<li>

<p id=style-no-external-resources>For the purpose of resolving URLs in STYLE blocks of a WebVTT
file, or any URLs in resources referenced from STYLE blocks of a WebVTT file, if the URL's
scheme is not "<code>data</code>", then the user agent must act as if the URL failed to
resolve.</p>

<p><strong class=advisement>Supporting external resources with ''@import'' or 'background-image'
would be a new ability for <a>media elements</a> and <a element>track</a> elements to issue
network requests as the user watches the video, which could be a privacy issue.</strong></p>

</li>

<li><p>For the purposes of processing by the CSS specification, <a lt="WebVTT Internal Node
Object">WebVTT Internal Node Objects</a> are equivalent to elements with the same
contents.</p></li>

<li>For the purposes of processing by the CSS specification, <a lt="WebVTT Text Object">WebVTT
Text Objects</a> are equivalent to {{Text}} nodes.</li>

<li>No style sheets are associated with |nodes|. (The nodes are subsequently restyled using style
sheets after their boxes are generated, as described below.)</li>

<li>The children of the |nodes| must be wrapped in an anonymous box whose 'display' property has
the value ''display/inline''. This is the <dfn>WebVTT cue background box</dfn>.</li>

<li>Runs of children of <a lt="WebVTT Ruby Object">WebVTT Ruby Objects</a> that are not <a
lt="WebVTT Ruby Text Object">WebVTT Ruby Text Objects</a> must be wrapped in anonymous boxes
whose 'display' property has the value ''display/ruby-base''. [[!CSS3-RUBY]]</li>

<li>Properties on <a lt="WebVTT Node Object">WebVTT Node Objects</a> have their values set as
defined in the next section. (That section uses some of the variables whose values were
calculated earlier in this algorithm.)</li>

<li>Text runs must be wrapped according to the CSS line-wrapping rules.</li>

<li>The viewport (and initial containing block) is |video|'s rendering area.</li>

</ul>

<p>Let |boxes| be the boxes generated as descendants of the initial containing block, along with
their positions.</p>

</li>
<li><p><a>Obtain a set of CSS boxes</a> |boxes| positioned relative to an initial containing
block.</p></li>

<li><p>If there are no line boxes in |boxes|, skip the remainder of these substeps for |cue|. The
cue is ignored.</p></li>
Expand Down Expand Up @@ -4674,8 +4568,112 @@ following algorithm.</p>
</ol>


<h4 id=applying-css-properties algorithm>Applying CSS properties to <a lt="WebVTT Node
Object">WebVTT Node Objects</a></h4>
<h3 id=obtaining-css-boxes algorithm>Obtaining CSS boxes</h3>

<p>When the processing algorithm above requires that the user agent <dfn>obtain a set of CSS
boxes</dfn> |boxes|, then apply the terms of the CSS specifications to |nodes| within the following
constraints: [[!CSS22]]</p>

<ul>

<li><p>The <i>document tree</i> is the tree of <a lt="WebVTT Node Object">WebVTT Node Objects</a>
rooted at |nodes|.</p></li>

<li>
<p>For the purpose of selectors in STYLE blocks of a WebVTT file, the style sheet must apply to a
hypothetical document that contains a single empty element with no explicit name, no namespace, no
attributes, no classes, no IDs, and unknown primary language, that acts like the <a>media
element</a> for the <a>text tracks</a> that were sourced from the given WebVTT file. The selectors
must not match other <a>text tracks</a> for the same <a>media element</a>. In this hypothetical
document, the element must not match any selector that would match the element itself.</p>

<p class=note>This element exists only to be the <a spec=selectors>originating element</a> for the
''::cue'', ''::cue()'', ''::cue-region'' and ''::cue-region()'' pseudo-elements.</p>
</li>

<li>
<p>For the purpose of determining the <a spec=css-cascade>cascade</a> of the declarations in STYLE
blocks of a WebVTT file, the relative order of appearance of the style sheets must be the same
order as they were added to the collection, and the order of appearance of the collection must be
after any style sheets that apply to the associated <a element>video</a> element's document.</p>

<div class=example>
<p>For example, given the following (invalid) HTML document:</p>

<pre>
&lt;!doctype html>
&lt;title>Invalid cascade example&lt;/title>
&lt;video controls autoplay src="video.webm">
&lt;track default src="track.vtt">
&lt;/video>
&lt;style>
::cue { color:red }
&lt;/style>
</pre>

<p>...and the "track.vtt" file contains:</p>

<pre>
WEBVTT

STYLE
::cue { color:lime }

00:00:00.000 --> 00:00:25.000
Red or green?
</pre>

<p>The ''color:lime'' declaration would win, because it is last in the <a
spec=css-cascade>cascade</a>, even though the <a element>style</a> element is after the <a
element>video</a> element in the document order.</p>
</div>
</li>

<li>

<p id=style-no-external-resources>For the purpose of resolving URLs in STYLE blocks of a WebVTT
file, or any URLs in resources referenced from STYLE blocks of a WebVTT file, if the URL's scheme
is not "<code>data</code>", then the user agent must act as if the URL failed to resolve.</p>

<p><strong class=advisement>Supporting external resources with ''@import'' or 'background-image'
would be a new ability for <a>media elements</a> and <a element>track</a> elements to issue
network requests as the user watches the video, which could be a privacy issue.</strong></p>

</li>

<li><p>For the purposes of processing by the CSS specification, <a lt="WebVTT Internal Node
Object">WebVTT Internal Node Objects</a> are equivalent to elements with the same
contents.</p></li>

<li>For the purposes of processing by the CSS specification, <a lt="WebVTT Text Object">WebVTT Text
Objects</a> are equivalent to {{Text}} nodes.</li>

<li>No style sheets are associated with |nodes|. (The nodes are subsequently restyled using style
sheets after their boxes are generated, as described below.)</li>

<li>The children of the |nodes| must be wrapped in an anonymous box whose 'display' property has
the value ''display/inline''. This is the <dfn>WebVTT cue background box</dfn>.</li>

<li>Runs of children of <a lt="WebVTT Ruby Object">WebVTT Ruby Objects</a> that are not <a
lt="WebVTT Ruby Text Object">WebVTT Ruby Text Objects</a> must be wrapped in anonymous boxes whose
'display' property has the value ''display/ruby-base''. [[!CSS3-RUBY]]</li>

<li>Properties on <a lt="WebVTT Node Object">WebVTT Node Objects</a> have their values set as
defined in the next section. (That section uses some of the variables whose values were calculated
earlier in this algorithm.)</li>

<li>Text runs must be wrapped according to the CSS line-wrapping rules.</li>

<li>The viewport (and initial containing block) is |video|'s rendering area.</li>

</ul>

<p>Let |boxes| be the boxes generated as descendants of the initial containing block, along with
their positions.</p>


<h3 id=applying-css-properties algorithm>Applying CSS properties to <a lt="WebVTT Node
Object">WebVTT Node Objects</a></h3>

<p>When following the <a>rules for updating the display of WebVTT text tracks</a>, user agents must
set properties of <a lt="WebVTT Node Object">WebVTT Node Objects</a> at the CSS user agent cascade
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