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Make the directionality account for missing parent element #9554

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Aug 29, 2023
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Make the directionality account for missing parent element #9554

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Make the directionality account for missing parent element
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Expand Up @@ -13443,161 +13443,167 @@ Transport Protocol">HTTP&lt;/abbr> today.&lt;/p></code></pre> <!-- DO NOT REWRAP
specifies the element's text directionality. The attribute is an <span>enumerated attribute</span>
with the following keywords and states:</p>

<dl>
<dt>The <dfn attr-value for="html-global/dir"><code data-x="attr-dir-ltr">ltr</code></dfn>
keyword, which maps to the <dfn data-x="attr-dir-ltr-state">ltr</dfn> state</dt>

<dd>
<p>Indicates that the contents of the element are explicitly directionally isolated
left-to-right text.</p>
</dd>

<dt>The <dfn attr-value for="html-global/dir"><code data-x="attr-dir-rtl">rtl</code></dfn>
keyword, which maps to the <dfn data-x="attr-dir-rtl-state">rtl</dfn> state</dt>

<dd>
<p>Indicates that the contents of the element are explicitly directionally isolated
right-to-left text.</p>
</dd>

<dt>The <dfn attr-value for="html-global/dir"><code data-x="attr-dir-auto">auto</code></dfn>
keyword, which maps to the <dfn data-x="attr-dir-auto-state">auto</dfn> state</dt>

<dd>
<p>Indicates that the contents of the element are explicitly directionally isolated text, but
that the direction is to be determined programmatically using the contents of the element (as
described below).</p>
<table>
<thead>
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<tr>
<th>Keyword</th>
<th>State</th>
<th>Brief description</th>
</tr>
</thead>
<tbody>
<tr>
<td><dfn attr-value for="html-global/dir"><code data-x="attr-dir-ltr">ltr</code></dfn></td>
<td><dfn data-x="attr-dir-ltr-state">ltr</dfn></td>
<td>The contents of the element are explicitly directionally isolated left-to-right text.</td>
</tr>
<tr>
<td><dfn attr-value for="html-global/dir"><code data-x="attr-dir-rtl">rtl</code></dfn></td>
<td><dfn data-x="attr-dir-rtl-state">rtl</dfn></td>
<td>The contents of the element are explicitly directionally isolated right-to-left text.</td>
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</tr>
<tr>
<td><dfn attr-value for="html-global/dir"><code data-x="attr-dir-auto">auto</code></dfn></td>
<td><dfn data-x="attr-dir-auto-state">auto</dfn></td>
<td>The contents of the element are explicitly directionally isolated text, but the direction
is to be determined programmatically using the contents of the element (as described
below).</td>
</tr>
</tbody>
</table>

<p class="note">The heuristic used by this state is very crude (it just looks at the first
character with a strong directionality, in a manner analogous to the Paragraph Level
determination in the bidirectional algorithm). Authors are urged to only use this value as a
last resort when the direction of the text is truly unknown and no better server-side heuristic
can be applied. <ref>BIDI</ref></p>
<div class="note">
<p>The heuristic used by the <span data-x="attr-dir-auto-state">auto</span> state is very crude
(it just looks at the first character with a strong directionality, in a manner analogous to the
Paragraph Level determination in the bidirectional algorithm). Authors are urged to only use this
value as a last resort when the direction of the text is truly unknown and no better server-side
heuristic can be applied. <ref>BIDI</ref></p>

<p class="note">For <code>textarea</code> and <code>pre</code> elements, the heuristic is
applied on a per-paragraph level.</p>
</dd>
</dl>
<p>For <code>textarea</code> and <code>pre</code> elements, the heuristic is applied on a
per-paragraph level.</p>
</div>

<p>The attribute has no <i data-x="invalid value default">invalid value default</i> and no <i data-x="missing value default">missing value default</i>.</p>
<p>The <code data-x="attr-dir">dir</code> attribute's <i data-x="invalid value default">invalid
value default</i> and <i data-x="missing value default">missing value default</i> are both the
<dfn data-x="attr-dir-undefined-state">undefined</dfn> state.</p>

<hr>

<p><dfn>The directionality</dfn> of an element (any element, not just an <span data-x="HTML
elements">HTML element</span>) is either '<dfn data-x="concept-ltr">ltr</dfn>' or '<dfn
data-x="concept-rtl">rtl</dfn>', and is determined as per the first appropriate set of steps from
the following list:</p>
<p>The <dfn data-x="the directionality">directionality</dfn> of an element (any element, not just
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Would it be appropriate to actually make this term actually be "directionality" rather than look like "directionality" in the defining instance but actually export/cross-link as "the directionality"? (maybe as a follow-up commit?) It's kinda weird as-is imho.

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This term isn't exported at all.

The data-x is purely a HTML-internal mechanism and doesn't show up anywhere.

an <span data-x="HTML elements">HTML element</span>) is either '<dfn
data-x="concept-ltr">ltr</dfn>' or '<dfn data-x="concept-rtl">rtl</dfn>'. To compute the <span
data-x="the directionality">directionality</span> given an element <var>element</var>, switch on
<var>element</var>'s <code data-x="attr-dir">dir</code> attribute state:</p>

<dl class="switch">
<dt><span data-x="attr-dir-ltr-state">ltr</span></dt>
<dd><p>Return '<span data-x="concept-ltr">ltr</span>'.</p></dd>

<dt><span data-x="attr-dir-rtl-state">rtl</span></dt>
<dd><p>Return '<span data-x="concept-rtl">rtl</span>'.</p></dd>

<dt>If the element's <code data-x="attr-dir">dir</code> attribute is in the <span
data-x="attr-dir-ltr-state">ltr</span> state</dt>

<dt>If the element is a <span>document element</span> and the <code data-x="attr-dir">dir</code>
attribute is not in a defined state (i.e. it is not present or has an invalid value)</dt>

<dt>If the element is an <code>input</code> element whose <code
data-x="attr-input-type">type</code> attribute is in the <span
data-x="attr-input-type-tel">Telephone</span> state, and the <code data-x="attr-dir">dir</code>
attribute is not in a defined state (i.e. it is not present or has an invalid value)</dt>

<dd><p><span>The directionality</span> of the element is '<span
data-x="concept-ltr">ltr</span>'.</p></dd>


<dt>If the element's <code data-x="attr-dir">dir</code> attribute is in the <span
data-x="attr-dir-rtl-state">rtl</span> state</dt>

<dd><p><span>The directionality</span> of the element is '<span
data-x="concept-rtl">rtl</span>'.</p></dd>

<dt>If the element is an <code>input</code> element whose <code
data-x="attr-input-type">type</code> attribute is in the <span
data-x="attr-input-type-text">Text</span>, <span data-x="attr-input-type-search">Search</span>,
<span data-x="attr-input-type-tel">Telephone</span>, <span
data-x="attr-input-type-url">URL</span>, or <span data-x="attr-input-type-email">Email</span>
state, and the <code data-x="attr-dir">dir</code> attribute is in the <span
data-x="attr-dir-auto-state">auto</span> state</dt>

<dt>If the element is a <code>textarea</code> element and the <code data-x="attr-dir">dir</code>
attribute is in the <span data-x="attr-dir-auto-state">auto</span> state</dt>
<dt><span data-x="attr-dir-auto-state">auto</span></dt>
<dd><p>Return the <span>auto directionality</span> of <var>element</var>.</p></dd>

<dt><span data-x="attr-dir-undefined-state">undefined</span></dt>
<dd>
<p>If the element's <span data-x="concept-fe-value">value</span> contains a character of
bidirectional character type AL or R, and there is no character of bidirectional character type
L anywhere before it in the element's <span data-x="concept-fe-value">value</span>, then
<span>the directionality</span> of the element is '<span data-x="concept-rtl">rtl</span>'.
<ref>BIDI</ref></p>
<ol>
<li><p>If <var>element</var> is a <code>bdi</code> element, then return the <span>auto
directionality</span> of <var>element</var>.</p></li>

<p>Otherwise, if the element's <span data-x="concept-fe-value">value</span> is not the empty
string, or if the element is a <span>document element</span>, <span>the directionality</span> of
the element is '<span data-x="concept-ltr">ltr</span>'.</p>
<li><p>If <var>element</var> is an <code>input</code> element whose <code
data-x="attr-input-type">type</code> attribute is in the <span
data-x="attr-input-type-tel">Telephone</span> state, then return '<span
data-x="concept-ltr">ltr</span>'.</p></li>

<p>Otherwise, <span>the directionality</span> of the element is the same as the element's parent
element's <span data-x="the directionality">directionality</span>.</p>
<li><p>Return the <span>parent directionality</span> of <var>element</var>.</p></li>
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</ol>
</dd>
</dl>

<p>To compute the <dfn>auto directionality</dfn> given an element <var>element</var>:</p>

<ol>
<li>
<p>If <var>element</var> is an <code>input</code> element whose <code
data-x="attr-input-type">type</code> attribute is in the <span
data-x="attr-input-type-text">Text</span>, <span data-x="attr-input-type-search">Search</span>,
<span data-x="attr-input-type-tel">Telephone</span>, <span
data-x="attr-input-type-url">URL</span>, or <span data-x="attr-input-type-email">Email</span>
state, or <var>element</var> is a <code>textarea</code> element, then:</p>

<dt>If the element's <code data-x="attr-dir">dir</code> attribute is in the <span
data-x="attr-dir-auto-state">auto</span> state</dt>

<dt>If the element is a <code>bdi</code> element and the <code data-x="attr-dir">dir</code>
attribute is not in a defined state (i.e. it is not present or has an invalid value)</dt>
<ol>
<li><p>If <var>element</var>'s <span data-x="concept-fe-value">value</span> contains a
character of bidirectional character type AL or R, and there is no character of bidirectional
character type L anywhere before it in the element's <span
data-x="concept-fe-value">value</span>, then return '<span data-x="concept-rtl">rtl</span>'.
<ref>BIDI</ref></p></li>

<dd>
<p>Find the first character in <span>tree order</span> that matches the following criteria:</p>
<li><p>If <var>element</var>'s <span data-x="concept-fe-value">value</span> is not the empty
string, then return '<span data-x="concept-ltr">ltr</span>'.</p></li>

<ul>
<li><p>Return the <span>parent directionality</span> of <var>element</var>.</p></li>
</ol>
</li>

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<li><p>The character is from a <code>Text</code> node that is a descendant of the element whose
<span data-x="the directionality">directionality</span> is being determined.</p></li>
<li><p>Let <var>codePoint</var> be null.</p></li>

<li><p>The character is of bidirectional character type L, AL, or R. <ref>BIDI</ref></li>
<li>
<p>For each <code>Text</code> node <var>text</var> that is a descendant of <var>element</var>,
in <span>tree order</span>:</p>

<ol>
<li>
<p>The character is not in a <code>Text</code> node that has an ancestor element that is a
descendant of the element whose <span data-x="the directionality">directionality</span> is
being determined and that is either:</p>
<p>If <var>text</var> has an ancestor element that is a descendant of <var>element</var> and
is also one of</p>
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<ul class="brief">
<li>A <code>bdi</code> element.
<li>A <code>script</code> element.
<li>A <code>style</code> element.
<li>A <code>textarea</code> element.
<li>An element with a <code data-x="attr-dir">dir</code> attribute in a defined state.
<li>a <code>bdi</code> element</li>
<li>a <code>script</code> element</li>
<li>a <code>style</code> element</li>
<li>a <code>textarea</code> element</li>
<li>an element whose <code data-x="attr-dir">dir</code> attribute is not in the <span
data-x="attr-dir-undefined-state">undefined</span> state</li>
</ul>

<p>then <span>continue</span>.</p>
</li>

</ul>
<li><p>If <var>text</var>'s <span data-x="concept-cd-data">data</span> does not contain a code
point whose bidirectional character type is L, AL, or R, then <span>continue</span>.
<ref>BIDI</ref></p></li>

<p>If such a character is found and it is of bidirectional character type AL or R, <span>the
directionality</span> of the element is '<span data-x="concept-rtl">rtl</span>'.</p>
<li><p>Set <var>codePoint</var> to the first code point in <var>text</var>'s <span
data-x="concept-cd-data">data</span> whose bidirectional character type is L, AL, or
R.</p></li>

<p>If such a character is found and it is of bidirectional character type L, <span>the
directionality</span> of the element is '<span data-x="concept-ltr">ltr</span>'.</p>
<li><p><span>Break</span>.</p></li>
</ol>
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I would combine these last two bullet points as ", then break", to mirror the structure of the previous line's ", then continue".

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We use then after an if statement, but not after a set. They could be combined with "and", but this is clearer.

</li>

<p>Otherwise, if the element is a <span>document element</span>, <span>the directionality</span>
of the element is '<span data-x="concept-ltr">ltr</span>'.</p>
<li><p>If <var>codePoint</var> is null, then return the <span>parent directionality</span> of
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<var>element</var>.</p></li>

<p>Otherwise, <span>the directionality</span> of the element is the same as the element's parent
element's <span data-x="the directionality">directionality</span>.</p>
</dd>
<li><p>If <var>codePoint</var> is of bidirectional character type AL or R, then return '<span
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data-x="concept-rtl">rtl</span>'.</p></li>

<li><p>If <var>codePoint</var> is of bidirectional character type L, then return '<span
data-x="concept-ltr">ltr</span>'.</p></li>
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@fantasai fantasai Aug 28, 2023 •
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I think this comment got lost in the GitHub interface, so copying it out here:

Might consider putting "If codepoint is ..." as a switch with 3 branches rather than 3 independent steps. They're not really ordered steps...

This helps group them conceptually, which imho makes the algorithm a little more structured and easier to understand as a series of higher-level steps.

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I like it as ordered steps; it's more clear how to translate into code.

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If the tests were of a different nature, that's more reasonable, but I think when it's purely dispatching based on different categorization of a single variable that's precisely what we have <dl class=switch> for.

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Not if the type of check you do on the variable differs.

</ol>

<dt>If the element has a parent element and the <code data-x="attr-dir">dir</code> attribute is
not in a defined state (i.e. it is not present or has an invalid value)</dt>
<p>To compute the <dfn>parent directionality</dfn> given an element <var>element</var>:</p>

<dd><p><span>The directionality</span> of the element is the same as the element's parent
element's <span data-x="the directionality">directionality</span>.</p></dd>
</dl>
<ol>
<li><p>If <var>element</var> has no <span>parent element</span>, then return '<span
data-x="concept-ltr">ltr</span>'.</p></li>

<li><p>Return <span data-x="the directionality">directionality</span> of <var>element</var>'s
<span data-x="parent element">parent</span>.</p></li>
</ol>

<p class="note">Since the <code data-x="attr-dir">dir</code> attribute is only defined for
<span>HTML elements</span>, it cannot be present on elements from other namespaces. Thus, elements
from other namespaces always just inherit their <span data-x="the
directionality">directionality</span> from their parent element, or, if they don't have one,
default to '<span data-x="concept-ltr">ltr</span>'.</p>
from other namespaces always end up using the <span>parent directionality</span>.</p>
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<div w-nodev>

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