[html5] r7062 - [giow] (0) Try to clarify line breaking, balancing, and bidi handling in WebVTT. [...]
whatwg at whatwg.org
whatwg at whatwg.org
Tue Apr 24 14:14:29 PDT 2012
Author: ianh
Date: 2012-04-24 14:14:28 -0700 (Tue, 24 Apr 2012)
New Revision: 7062
Modified:
source
Log:
[giow] (0) Try to clarify line breaking, balancing, and bidi handling in WebVTT.
Affected topics: Video Text Tracks
Modified: source
===================================================================
--- source 2012-04-19 23:53:03 UTC (rev 7061)
+++ source 2012-04-24 21:14:28 UTC (rev 7062)
@@ -108925,22 +108925,13 @@
<li>
<p>Apply the Unicode Bidirectional Algorithm's Paragraph Level
- steps to <var title="">nodes</var> using the following
- constraints, to determine the <i>paragraph embedding level</i>
- of the cue: <a href="#refsBIDI">[BIDI]</a></p>
+ steps to the concatenation of the values of each <span>WebVTT
+ Text Object</span> in <var title="">nodes</var>, in a pre-order,
+ depth-first traversal, excluding <span title="WebVTT Ruby Text
+ Object">WebVTT Ruby Text Objects</span> and their descendants,
+ to determine the <i>paragraph embedding level</i> of the first
+ Unicode paragraph of the cue. <a href="#refsBIDI">[BIDI]</a></p>
- <ul>
-
- <li><var title="">nodes</var> represents a single paragraph.</li>
-
- <li>The paragraph's text consists of the concatenation of the
- values of each <span>WebVTT Text Object</span> in <var
- title="">nodes</var>, in a pre-order, depth-first traversal,
- excluding <span title="WebVTT Ruby Text Object">WebVTT Ruby
- Text Objects</span> and their descendants.</li>
-
- </ul>
-
</li>
<li>
@@ -109205,15 +109196,31 @@
were calculated earlier in this algorithm.)</li>
<li>Text runs must be wrapped according to the CSS
- line-wrapping rules, except that additionally, regardless of
- the value of the 'white-space' property, lines must be wrapped
- at the edge of their containing blocks, even if doing so
- requires splitting a word where there is no line breaking
- opportunity. (Thus, normally text wraps as needed, but if there
- is a particularly long word, it does not overflow as it
- normally would in CSS, it is instead forcibly wrapped at the
- box's edge.)</li>
+ line-wrapping rules, with the following additional constraints:
+ <ul>
+
+ <li>Regardless of the value of the 'white-space' property,
+ lines must be wrapped at the edge of their containing blocks,
+ even if doing so requires splitting a word where there is no
+ line breaking opportunity. (Thus, normally text wraps as
+ needed, but if there is a particularly long word, it does not
+ overflow as it normally would in CSS, it is instead forcibly
+ wrapped at the box's edge.)</li>
+
+ <li>Regardless of the value of the 'white-space' property,
+ any line breaks inserted by the user agent for the purposes
+ of line wrapping must be placed so as to minimise Δ
+ across each run of consecutive lines between preserved
+ newlines in the source. Δ for a set of lines is defined
+ as the sum over each line of the absolute of the difference
+ between the line's length and the mean line length of the
+ set.</li>
+
+ </ul>
+
+ </li>
+
<li>The viewport (and initial containing block) is
<var title="">video</var>'s rendering area.</li>
@@ -109522,8 +109529,9 @@
<p>When following the <span>rules for updating the display of WebVTT
text tracks</span>, user agents must set properties of <span
- title="WebVTT Node Object">WebVTT Node Objects</span> as defined in
- this section. <a href="#refsCSS">[CSS]</a></p>
+ title="WebVTT Node Object">WebVTT Node Objects</span> at the CSS
+ user agent cascade layer as defined in this section. <a
+ href="#refsCSS">[CSS]</a></p>
<p>On the (root) <span>List of WebVTT Node Objects</span>, the
'position' property must be set to 'absolute', the 'direction'
@@ -109573,6 +109581,10 @@
of WebVTT Node Objects</span>, if supported.</p> <!-- 'text-outline'
is in CSS3 Text, but Tab says that's awaiting medical attention. -->
+ <p>The 'white-space' property on the (root) <span>List of WebVTT
+ Node Objects</span> must be set to 'pre-wrap'. <a
+ href="#refsCSS">[CSS]</a></p>
+
<p>The 'font-style' property on <span title="WebVTT Italic
Object">WebVTT Italic Objects</span> must be set to 'italic'.</p>
@@ -109590,10 +109602,6 @@
Object">WebVTT Ruby Text Objects</span> must be set to
'ruby-text'. <a href="#refsCSSRUBY">[CSSRUBY]</a></p>
- <p>If there are style sheets that apply to the <span>media
- element</span> or other playback mechanism, then they must be
- interpreted as defined in the next section.</p>
-
<p>All other non-inherited properties must be set to their initial
values; inherited properties on the root <span>List of WebVTT Node
Objects</span> must inherit their values from the <span>media
@@ -109604,7 +109612,11 @@
<span>List of WebVTT Node Objects</span> must take their initial
values.</p>
+ <p>If there are style sheets that apply to the <span>media
+ element</span> or other playback mechanism, then they must be
+ interpreted as defined in the next section.</p>
+
<h4>CSS extensions</h4>
<p>When a user agent is rendering one or more <span title="text
@@ -109659,6 +109671,7 @@
<li>the properties corresponding to the 'background' shorthand</li>
<li>the properties corresponding to the 'outline' shorthand</li>
<li>the properties corresponding to the 'font' shorthand, including 'line-height'</li>
+ <li>'white-space'</li>
<!-- add more... -->
<!-- definitely not:
display, float, position, top, left, right, bottom, width,
@@ -109780,7 +109793,7 @@
<li>the properties corresponding to the 'outline' shorthand</li>
<li>properties relating to the transition and animation features</li>
<!-- add more... -->
- <!-- but definitely not anything that affects dimensions of boxes, e.g. the 'font' shorthand's properties -->
+ <!-- but definitely not anything that affects dimensions of boxes, e.g. the 'font' shorthand's properties or 'white-space'; those are listed below instead -->
</ul>
<!--v2
@@ -109798,6 +109811,7 @@
<ul class="brief">
<li>the properties corresponding to the 'font' shorthand, including 'line-height'</li>
+ <li>'white-space'</li>
<!-- add more... -->
<!-- definitely not:
display, float, position, top, left, right, bottom, width,
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