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Define required precision, and split up ranges by type. Put it all into an appendix. Define rounding behavior of computed values.
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‎css3-values/Overview.html‎

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dt + dt::before { content: ", "; }
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dt { display: inline; }
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:not(code) var { font-style: normal; color: #005A9C; }
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td > small { display: block; }
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</style>
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<link href="../default.css" rel=stylesheet type="text/css">
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<link href="http://www.w3.org/StyleSheets/TR/W3C-ED.css" rel=stylesheet
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<h1>CSS Values and Units Module Level 3</h1>
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<h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 22 May 2012</h2>
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<h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 23 May 2012</h2>
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<dl>
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<dt>This version:
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<dd><a
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href="http://www.w3.org/TR/2012/ED-css3-values-20120522/">http://www.w3.org/TR/2012/ED-css3-values-20120522/</a>
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href="http://www.w3.org/TR/2012/ED-css3-values-20120523/">http://www.w3.org/TR/2012/ED-css3-values-20120523/</a>
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<dt>Latest version:
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@@ -297,9 +298,12 @@ <h2 class="no-num no-toc" id=contents>Table of contents</h2>
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References: ‘<code class=css>attr()</code>’</a>
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</ul>
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<li><a href="#required-ranges"><span class=secno>9. </span> Appendix A:
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Recommended Minimum Ranges and Precision of Computed Values</a>
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<li class=no-num><a href="#acknowledgments">Acknowledgments</a>
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<li><a href="#conformance"><span class=secno>9. </span> Conformance</a>
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<li class=no-num><a href="#conformance"> Conformance</a>
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<ul class=toc>
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<li><a href="#conventions"><span class=secno>9.1. </span> Document
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conventions</a>
@@ -747,16 +751,13 @@ <h2 id=numeric-types><span class=secno>4. </span> Numeric Data Types</h2>
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<p> Properties may restrict numeric values to some range. If the value is
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outside the allowed range, the declaration is invalid and must be <a
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href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignored</a>. For
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unrestricted values, UAs must support at least up to ±2<sup>24</sup>-1;
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unsupported values must be clamped to the closest supported value. When
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arithmetic is performed with numeric types (for example, in the calc()
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expression, or when doing unit conversions), if the result is outside the
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UAs's supported range, it must also be clamped to the closest supported
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value.
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href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignored</a>.
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<p> UAs must support at least 3 digits of precision after the decimal point
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in numeric values.
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<p> CSS theoretically supports infinite precision and infinite ranges for
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all value types; however in reality implementations have finite capacity.
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The recommended minimum ranges and precision, and the required rounding
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and clamping rules, are given in <a href="#required-ranges">Appendix
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A</a>.
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<h3 id=integers><span class=secno>4.1. </span> Integers: the ‘<a
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href="#integer-value"><code class=css>&lt;integer></code></a>’ type</h3>
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versions of CSS may extend ‘<a href="#attr"><code
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class=css>attr()</code></a>’ in this direction.
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<h2 id=required-ranges><span class=secno>9. </span> Appendix A: Recommended
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Minimum Ranges and Precision of Computed Values</h2>
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<p> For unrestricted values, the recommended minimum range and precision of
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computed values is given in the table below.
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<table class=data>
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<thead>
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<tr>
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<th>Type
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<th>Recommended Minimum Precision
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<th>Recommended Minimum Maximum (Absolute Value)
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<tbody>
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<tr>
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<th><a href="#integer-value"><var>&lt;integer></var></a>
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<td>1
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<td>2<sup>24</sup>−1
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<tr>
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<th><a href="#number-value"><var>&lt;number></var></a>
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<td>0.01 <small>(within the range -100 &lt; <var>x</var> &lt;
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100)</small>
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<td>2<sup>17</sup>−1
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<tr>
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<th><a href="#percentage-value"><var>&lt;percentage></var></a>
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<td>0.01% <small>(within the range -100 &lt; <var>x</var> &lt;
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100)</small>
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<td>(2<sup>17</sup>−1)%
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<tr>
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<th><a href="#length-value"><var>&lt;length></var></a>
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<td>0.1px
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<td>(2<sup>24</sup>−1)px
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<tr>
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<th><a href="#angle-value"><var>&lt;angle></var></a>
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<td>0.1deg
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<td>(2<sup>24</sup>−1)deg
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<tr>
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<th><a href="#time-value"><var>&lt;time></var></a>
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<td>1ms
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<td>(2<sup>24</sup>−1)ms
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<tr>
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<th><a href="#frequency-value"><var>&lt;frequency></var></a>
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<td>0.01Hz
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<td>(2<sup>17</sup>−1)Hz
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</table>
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<p> Values outside the supported range must be clamped into the supported
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range. Values specified with an unsupported amount of precision must be
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rounded to the closest supported value; except that values that are not
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equal to, but would round to, either zero or the boundary of a closed
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range, are rounded away from that value rather than to it.
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<div class=example>
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<p> For example, in a UA that only supports a precision of 0.01, an
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‘<code class=property>opacity</code>’ value of ‘<code
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class=css>0.9999</code>’ would round to ‘<code
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class=css>0.99</code>’, not ‘<code class=css>1.0</code>’, and would
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therefore cause the element to create a stacking context. Similarly, a
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‘<code class=css>flex-grow</code>’ value of ‘<code
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class=css>0.001</code>’ would round to ‘<code
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class=css>0.01</code>’, not ‘<code class=css>0</code>’, and would
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therefore be flexible.
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</div>
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<p> When arithmetic is performed with numeric types (for example, in the
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‘<a href="#calc"><code class=css>calc()</code></a>’ expression), if
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the result is unsupported it must also be clamped/rounded as necessary.
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<span class=note> Note this means that rounding errors <em>may</em>
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accumulate. </span>
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<h2 class=no-num id=acknowledgments>Acknowledgments</h2>
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<p>Comments and suggestions from Giovanni Campagna, Christoph Päper, Keith
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Rarick, Alex Mogilevsky, Ian Hickson, David Baron, Edward Welbourne, Boris
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Zbarsky, Björn Höhrmann and Michael Day improved this module.
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<h2 id=conformance><span class=secno>9. </span> Conformance</h2>
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<h2 class=no-num id=conformance> Conformance</h2>
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<h3 id=conventions><span class=secno>9.1. </span> Document conventions</h3>
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‎css3-values/Overview.src.html‎

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dt + dt::before { content: ", "; }
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dt { display: inline; }
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:not(code) var { font-style: normal; color: #005A9C; }
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td > small { display: block; }
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</style>
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<link rel="stylesheet" type="text/css" href="../default.css">
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<link rel="stylesheet" type="text/css" href="http://www.w3.org/StyleSheets/TR/W3C-[STATUS].css">
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Properties may restrict numeric values to some range.
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If the value is outside the allowed range,
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the declaration is invalid and must be <a href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignored</a>.
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For unrestricted values, UAs must support at least up to ±2<sup>24</sup>-1;
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unsupported values must be clamped to the closest supported value.
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When arithmetic is performed with numeric types
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(for example, in the calc() expression, or when doing unit conversions),
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if the result is outside the UAs's supported range,
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it must also be clamped to the closest supported value.
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<p>
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UAs must support at least 3 digits of precision after the decimal point in numeric values.
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CSS theoretically supports infinite precision and infinite ranges for all value types;
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however in reality implementations have finite capacity.
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The recommended minimum ranges and precision,
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and the required rounding and clamping rules,
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are given in <a href="#required-ranges">Appendix A</a>.
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<h3 id="integers">
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Integers: the ''&lt;integer>'' type</h3>
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another attribute. Future versions of CSS may extend ''attr()'' in this
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direction.</p>
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<h2 id="required-ranges">
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Appendix A: Recommended Minimum Ranges and Precision of Computed Values</h2>
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<p>
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For unrestricted values, the recommended minimum range and precision
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of computed values
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is given in the table below.
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<table class="data">
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<thead>
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<tr><th>Type
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<th>Recommended Minimum Precision
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<th>Recommended Minimum Maximum (Absolute Value)
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</thead>
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<tbody>
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<tr><th><var>&lt;integer></var>
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<td>1
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<td>2<sup>24</sup>&minus;1
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<tr><th><var>&lt;number></var>
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<td>0.01
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<small>(within the range -100 &lt; <var>x</var> &lt; 100)</small>
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<td>2<sup>17</sup>&minus;1
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<tr><th><var>&lt;percentage></var>
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<td>0.01%
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<small>(within the range -100 &lt; <var>x</var> &lt; 100)</small>
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<td>(2<sup>17</sup>&minus;1)%
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<tr><th><var>&lt;length></var>
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<td>0.1px
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<td>(2<sup>24</sup>&minus;1)px
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<tr><th><var>&lt;angle></var>
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<td>0.1deg
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<td>(2<sup>24</sup>&minus;1)deg
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<tr><th><var>&lt;time></var>
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<td>1ms
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<td>(2<sup>24</sup>&minus;1)ms
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<tr><th><var>&lt;frequency></var>
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<td>0.01Hz
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<td>(2<sup>17</sup>&minus;1)Hz
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</tbody>
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</table>
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<p>
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Values outside the supported range must be clamped into the supported range.
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Values specified with an unsupported amount of precision must be rounded
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to the closest supported value;
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except that values that are not equal to, but would round to,
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either zero or the boundary of a closed range,
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are rounded away from that value rather than to it.
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<div class="example">
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<p>
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For example, in a UA that only supports a precision of 0.01,
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an 'opacity' value of ''0.9999'' would round to ''0.99'', not ''1.0'',
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and would therefore cause the element to create a stacking context.
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Similarly, a ''flex-grow'' value of ''0.001'' would round to ''0.01'',
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not ''0'', and would therefore be flexible.
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</div>
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<p>
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When arithmetic is performed with numeric types
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(for example, in the ''calc()'' expression),
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if the result is unsupported
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it must also be clamped/rounded as necessary.
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<span class="note">
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Note this means that rounding errors <em>may</em> accumulate.
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<h2 class="no-num" id="acknowledgments">Acknowledgments</h2>
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<p>Comments and suggestions from Giovanni Campagna, Christoph P&auml;per, Keith Rarick, Alex Mogilevsky, Ian Hickson, David Baron, Edward Welbourne, Boris Zbarsky, Bj&ouml;rn H&ouml;hrmann and Michael Day improved this module.
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<h2 id="conformance">
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<h2 class="no-num" id="conformance">
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Conformance</h2>
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<h3 id="conventions">

‎css3-values/issues-lc-2012.txt‎

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From: Kenny Lu
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Comment: http://lists.w3.org/Archives/Public/www-style/2012Apr/0080.html
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Response: http://lists.w3.org/Archives/Public/www-style/2012Apr/0631.html
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Open: Exact spec edits depend on a 2.1 issue resolution.
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Closed: Mostly accepted
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----
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Issue 21.
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Summary: attr() and cycle() must be "valid where they are placed", but can resolve as multiple types
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From: Kenny Lu
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Comment: http://lists.w3.org/Archives/Public/www-style/2012Apr/0151.html
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Response: http://lists.w3.org/Archives/Public/www-style/2012Apr/0626.html
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Open: Accepted pending WG resolution
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Closed: Accepted
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----
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Issue 22.
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Summary: Required ranges for all the values seem random or incorrect
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From: Kenny Lu
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Comment: http://lists.w3.org/Archives/Public/www-style/2012Apr/0403.html
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Response: http://lists.w3.org/Archives/Public/www-style/2012Apr/0633.html
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Comment: http://lists.w3.org/Archives/Public/www-style/2012Apr/0530.html
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Open: Accepted pending WG resolution
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Open: Accepted
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----
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Issue 23.
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Summary: When does clamping happen in calc()?
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From: Kenny Lu
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Comment: http://lists.w3.org/Archives/Public/www-style/2012Apr/0405.html
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Response: http://lists.w3.org/Archives/Public/www-style/2012Apr/0416.html
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Open: Accepted pending WG resolution
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Open: Accepted
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----
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Issue 25.
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Summary: Define "required precision" for numbers.
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From: Arron Eicholz
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Comment: (private comment)
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Open: Accepted pending WG resolution
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Open: Accepted pending proposal + WG resolution
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Note: Made a required precision of 3 decimal digits.
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----
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Issue 26.
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Response:
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Closed: Deferred
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----
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Issue 28.
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Summary: Define normalization handling of <author-ident>
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From: fantasai
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Comment: http://lists.w3.org/Archives/Public/www-style/2012May/0026.html
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Response:
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Open
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----
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Issue 29.
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Summary: Case-sensitivity of <author-ident>
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From: fantasai + Tab Atkins
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Comment: http://lists.w3.org/Archives/Public/www-style/2012May/0499.html
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Open
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----
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Issue 30.
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Summary: Add <positive-integer> and <non-negative-integer> types
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From: Brian Manthos
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Comment: http://lists.w3.org/Archives/Public/www-style/2012May/0343.html
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Closed: Deferred
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----

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