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Adjust rules for parsing dimension values #4747

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Jul 3, 2019
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Adjust rules for parsing dimension values #4747

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aeaf0b4
Adjust rules for parsing dimension values
annevk Jul 1, 2019
cc897e5
disallow leading dot as Chrome does not support that
annevk Jul 2, 2019
609fe8c
make language consistent; adopt Infra language
annevk Jul 2, 2019
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81 changes: 45 additions & 36 deletions source
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Expand Up @@ -4887,10 +4887,11 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute

<p>The <dfn>rules for parsing dimension values</dfn> are as given in the following algorithm. When
invoked, the steps must be followed in the order given, aborting at the first step that returns a
value. This algorithm will return either a number greater than or equal to 0.0, or an error; if a
value. This algorithm will return either a number greater than or equal to 0.0, or failure; if a
number is returned, then it is further categorized as either a percentage or a length.</p>

<ol>
<li><p>Let <var>value</var> be null.</p></li>

<li><p>Let <var>input</var> be the string being parsed.</p></li>

Expand All @@ -4900,66 +4901,74 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
<li><p><span>Skip ASCII whitespace</span> within <var>input</var> given
<var>position</var>.</p></li>

<li><p>If <var>position</var> is past the end of <var>input</var>, return an error.</p></li>

<li><p>If the character indicated by <var>position</var> is a U+002B PLUS SIGN character (+),
advance <var>position</var> to the next character.</li>

<li><p>If <var>position</var> is past the end of <var>input</var>, return an error.</p></li>

<li><p>If the character indicated by <var>position</var> is not an <span data-x="ASCII
digits">ASCII digit</span>, then return an error.</p></li>
<li><p>If <var>position</var> is past the end of <var>input</var>, return failure.</p></li>

<!-- Ok. At this point we know we have a number. It might have trailing garbage which we'll
ignore, but it's a number, and we won't return an error. -->
<li>
<p>If the character indicated by <var>position</var> is an <span data-x="ASCII digits">ASCII
digit</span>, then:

<li><p><span>Collect a sequence of code points</span> that are <span>ASCII digits</span> from
<var>input</var> given <var>position</var>, and interpret the resulting sequence as a base-ten
integer. Let <var>value</var> be that number.</li>
<ol>
<li><p><span>Collect a sequence of code points</span> that are <span>ASCII digits</span> from
<var>input</var> given <var>position</var>, and interpret the resulting sequence as a base-ten
integer. Set <var>value</var> to that number.</p></li>

<li><p>If <var>position</var> is past the end of <var>input</var>, return <var>value</var> as a
length.</p></li>
<li><p>If <var>position</var> is past the end of <var>input</var>, return <var>value</var> as a
length.</p></li>
</ol>

<li>

<p>If the character indicated by <var>position</var> is a U+002E FULL STOP character (.):</p>
<p>If the character indicated by <var>position</var> is U+002E (.), then:</p>

<ol>

<li><p>Advance <var>position</var> to the next character.</p></li>

<li><p>If <var>position</var> is past the end of <var>input</var>, or if the character
indicated by <var>position</var> is not an <span data-x="ASCII digits">ASCII digit</span>, then
return <var>value</var> as a length.</li>
<li><p>If <var>position</var> is past the end of <var>input</var> or if the character indicated
by <var>position</var> is not an <span data-x="ASCII digits">ASCII digit</span>, then return
the <span>current dimension value</span> with <var>value</var>, <var>input</var>, and
<var>position</var>.</p></li>

<li><p>If <var>value</var> is null, then set <var>value</var> to 0.</p></li>

<li><p>Let <var>divisor</var> have the value 1.</p></li>

<li><p><i>Fraction loop</i>: Multiply <var>divisor</var> by ten.</p></li>
<li>
<p>While true:</p>

<li>Add the value of the character indicated by <var>position</var>, interpreted as a base-ten
digit (0..9) and divided by <var>divisor</var>, to <var>value</var>.</li>
<ol>
<li><p>Multiply <var>divisor</var> by ten.</p></li>

<li><p>Advance <var>position</var> to the next character.</p></li>
<li><p>Add the value of the character indicated by <var>position</var>, interpreted as a
base-ten digit (0..9) and divided by <var>divisor</var>, to <var>value</var>.</p></li>

<li><p>If <var>position</var> is past the end of <var>input</var>, then return <var>value</var>
as a length.</li>
<li><p>Advance <var>position</var> to the next character.</p></li>

<li><p>If the character indicated by <var>position</var> is an <span data-x="ASCII
digits">ASCII digit</span>, return to the step labeled <i>fraction loop</i> in these
substeps.</p></li>
<li><p>If <var>position</var> is past the end of <var>input</var>, then return
<var>value</var> as a length.</p></li>

<li><p>If the character indicated by <var>position</var> is not an <span data-x="ASCII
digits">ASCII digit</span>, then <span>break</span>.</p></li>
</ol>
</li>
</ol>

</li>

<li><p>Return the <span>current dimension value</span> with <var>value</var>, <var>input</var>,
and <var>position</var>.</p></li>
</ol>

<p>The <dfn>current dimension value</dfn>, given <var>value</var>, <var>input</var>, and
<var>position</var>, is determined as follows:</p>

<ol>
<li><p>If <var>value</var> is null, then return failure.</p></li>

<li><p>If <var>position</var> is past the end of <var>input</var>, return <var>value</var> as a
length.</p></li>

<li><p>If the character indicated by <var>position</var> is a U+0025 PERCENT SIGN character (%),
return <var>value</var> as a percentage.</p></li>
<li><p>If the character indicated by <var>position</var> is U+0025 (%), then return
<var>value</var> as a percentage.</p></li>

<li><p>Return <var>value</var> as a length.</p></li>

</ol>

<h5>Non-zero percentages and lengths</h5>
Expand Down