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Add a lang IDL Attribute to CanvasTextDrawingStyles, and clarify "direction" on same #10873

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Add a lang IDL Attribute to CanvasTextDrawingStyles, and clarify "direction" on same #10873

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eba506c
Add the lang IDL attribute to CanvasTextDrawingStyles
schenney-chromium Dec 18, 2024
caa22ca
Merge branch 'whatwg:main' into main
schenney-chromium Dec 18, 2024
488b95b
Fix Developer info
schenney-chromium Dec 18, 2024
01e6185
Merge branch 'whatwg:main' into main
schenney-chromium Jan 10, 2025
b6df5ee
Merge branch 'whatwg:main' into main
schenney-chromium Jan 22, 2025
1b5a1df
Post review revisions
schenney-chromium Jan 22, 2025
152e3a4
Clean up offscreen snapshot behavior
schenney-chromium Jan 23, 2025
60a5971
Fix the setter/getter for lang.
schenney-chromium Jan 23, 2025
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Original file line number Diff line number Diff line change
Expand Up @@ -65339,6 +65339,14 @@ callback <dfn callback>BlobCallback</dfn> = undefined (<span>Blob</span>? blob);
<li><p>Set this <code>canvas</code> element's <span data-x="concept-canvas-context-mode">context
mode</span> to <span data-x="concept-canvas-placeholder">placeholder</span>.</p></li>

<li><p>Set the <span data-x="offscreencanvas-inherited-lang">inherited language</span> of
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Nit (to be applied throughout this PR):

Set offscreenCanvas's inherited language to this canvas element's language.

(There's further modernization to be done here, but let's consider that out-of-scope.)

<var>offscreenCanvas</var> to the <span data-x="language">language</span> of this
<code>canvas</code> element.</p></li>

<li><p>Set the <span data-x="offscreencanvas-inherited-direction">inherited direction</span> of
<var>offscreenCanvas</var> to the <span data-x="the directionality">directionality</span> of this
<code>canvas</code> element.</p></li>

<li><p>Return <var>offscreenCanvas</var>.</p></li>
</ol>

Expand Down Expand Up @@ -65549,6 +65557,7 @@ interface mixin <dfn interface>CanvasPathDrawingStyles</dfn> {

interface mixin <dfn interface>CanvasTextDrawingStyles</dfn> {
// text
attribute DOMString <span data-x="dom-context-2d-lang">lang</span>; // (default: "inherit")
attribute DOMString <span data-x="dom-context-2d-font">font</span>; // (default 10px sans-serif)
attribute <span>CanvasTextAlign</span> <span data-x="dom-context-2d-textAlign">textAlign</span>; // (default: "start")
attribute <span>CanvasTextBaseline</span> <span data-x="dom-context-2d-textBaseline">textBaseline</span>; // (default: "alphabetic")
Expand Down Expand Up @@ -66022,6 +66031,7 @@ context.fillRect(100,0,50,50); // only this square remains</code></pre>
data-x="dom-context-2d-shadowOffsetX">shadowOffsetX</code>, <code
data-x="dom-context-2d-shadowOffsetY">shadowOffsetY</code>, <code
data-x="dom-context-2d-shadowBlur">shadowBlur</code>, <code
data-x="dom-context-2d-lang">lang</code>, <code
data-x="dom-context-2d-font">font</code>, <code
data-x="dom-context-2d-textAlign">textAlign</code>, <code
data-x="dom-context-2d-textBaseline">textBaseline</code>, <code
Expand Down Expand Up @@ -66516,13 +66526,26 @@ transform. ack Shaun Morris. -->
<h6>Text styles</h6>

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Nit: seems more correct to refer to something like dom-context-2d-lang-inherit. The same below.

<dl class="domintro">
<dt><code data-x=""><var>context</var>.<span subdfn data-x="dom-context-2d-lang">lang</span> [ = <var>value</var> ]</code></dt>
<dt><code data-x=""><var>styles</var>.<span data-x="dom-context-2d-lang">lang</span> [ = <var>value</var> ]</code></dt>
<dd>
<p>Returns the current language setting.</p>

<p>Can be set, to change the language used when resolving fonts. The syntax and valid values
are the same as those for the <span data-x="attr-lang">lang</span> element attribute, or the
value "<code data-x="dom-context-2d-direction-inherit">inherit</code>" which is described
below.</p>

<p>The default is "<code data-x="dom-context-2d-direction-inherit">inherit</code>".</p>
</dd>

<dt><code data-x=""><var>context</var>.<span subdfn data-x="dom-context-2d-font">font</span> [ = <var>value</var> ]</code></dt>
<dt><code data-x=""><var>styles</var>.<span data-x="dom-context-2d-font">font</span> [ = <var>value</var> ]</code></dt>
<dd>
<p>Returns the current font settings.</p>

<p>Can be set, to change the font. The syntax is the same as for the CSS <span>'font'</span>
property; values that cannot be parsed as CSS font values are ignored.</p>
property; values that cannot be parsed as CSS font values are ignored. The default is "10px sans-serif".</p>
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We wrap at a 100 columns.


<p>Relative keywords and lengths are computed relative to the font of the <code>canvas</code>
element.</p>
Expand Down Expand Up @@ -66694,15 +66717,51 @@ worker.postMessage(offscreenCanvas, [offscreenCanvas]);</code></pre>
Notice that the font is only loaded inside the worker, and not in the document context.</p>
</div>

<p>Objects that implement the <code>CanvasTextDrawingStyles</code> interface have a <dfn attribute
for="CanvasTextDrawingStyles"><code data-x="dom-context-2d-lang">lang</code></dfn> attribute
that controls localization of the font. The <code data-x="dom-context-2d-lang">lang</code> IDL
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attribute, on getting, must return the current value. The <code
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Couple issues here:

  1. "The lang getter steps are to return ..."
  2. It needs to return the value of some internal concept, similar to what letterSpacing does.
  3. It should probably be its own paragraph. We no longer really define getters and setters and concepts all in one paragraph.

data-x="dom-context-2d-lang">lang</code> setter steps are:</p>

<ol>
<li><p>Change the current value to the new value.</p></li>
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This needs to manipulate an internal concept.

<li><p>Set the <dfn data-x="dom-context-2d-font-language">language for the font</dfn> using the
following steps:</p>
Comment on lines +66728 to +66729
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This statement seems redundant with subsequent statements. I suggest we drop it.

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Perhaps this is meant to be the internal language concept? But if so we shouldn't define it inline in the algorithm.

<ol>
<li><p>If the value is "<code data-x="dom-context-2d-direction-inherit">inherit</code>", then</p>
<ol>
<li><p>If <var>object</var>'s <span>font style source object</span> is a <code>canvas</code>
element, then set the <span data-x="dom-context-2d-font-language">language for the
font</span> to the element's <span data-x="language">language</span>.</p></li>

<li><p>Otherwise, <var>object</var>'s <span>font style source object</span> is an
<code>OffscreenCanvas</code> object/ Set the <span data-x="dom-context-2d-font-language">
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We don't want this kind of specification style (or "COME FROM"). This makes the model very hard to understand. Instead we should propagate this state in the same place where you'd implement it, the transferControlToOffscreen() definition.

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To be sure I understand, I would modify the algorithm for creating offscreen canvas objects to include the steps to capture the direction and language when the object is created. Is that right? It sure makes sense to me and addresses something I thought was not well explained.

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Yeah and you'll have to store them somewhere so you also have to create some internal fields on OffscreenCanvas to capture the values in.

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Done, I think.

language for the font</span> to the <code>OffscreenCanvas</code>'s internal
<span data-x="offscreencanvas-inherited-lang">inherited language</span>.</p></li>
</ol>
</li>
<li><p>Otherwise, the <span data-x="dom-context-2d-font-language">language for the font</span>
is the value.</p></li>
</ol>
</li>
</ol>

<p>When the object implementing the <code>CanvasTextDrawingStyles</code> interface is created,
the <code data-x="dom-context-2d-lang">lang</code> attribute must initially have the value
"<code data-x="dom-context-2d-direction-inherit">inherit</code>" and the
<span data-x="dom-context-2d-font-language">language for the font</span> must be set as above.</p>

<p>The <dfn attribute for="CanvasTextDrawingStyles"><code
data-x="dom-context-2d-font">font</code></dfn> IDL attribute, on setting, must be <span
data-x="parse something according to a CSS grammar">parsed as a CSS &lt;'font'> value</span> (but
without supporting property-independent style sheet syntax like 'inherit'), and the resulting font
must be assigned to the context, with the <span>'line-height'</span> component forced to 'normal',
with the <span>'font-size'</span> component converted to <span data-x="'px'">CSS pixels</span>,
and with system fonts being computed to explicit values. If the new value is syntactically
incorrect (including using property-independent style sheet syntax like 'inherit' or 'initial'),
then it must be ignored, without assigning a new font value. <ref>CSS</ref></p>
must be assigned to the context, with the <span data-x="dom-context-2d-font-language">language
for the font</span> as determined above, with the <span>'line-height'</span>
component forced to 'normal', with the <span>'font-size'</span> component converted to <span
data-x="'px'">CSS pixels</span>, and with system fonts being computed to explicit values. If the
new value is syntactically incorrect (including using property-independent style sheet syntax
like 'inherit' or 'initial'), then it must be ignored, without assigning a new font value.
<ref>CSS</ref></p>

<p>Font family names must be interpreted in the context of the <span>font style source
object</span> when the font is to be used; any fonts embedded using <code
Expand Down Expand Up @@ -66900,16 +66959,30 @@ worker.postMessage(offscreenCanvas, [offscreenCanvas]);</code></pre>

<dd><p>Treat input to the <span>text preparation algorithm</span> as right-to-left text.</p></dd>

<!--
<dt><dfn><code data-x="dom-context-2d-direction-auto">auto</code></dfn>
<dt><dfn enum-value for="CanvasDirection"><code data-x="dom-context-2d-direction-inherit">inherit</code></dfn>

<dd><p>Determine the direction from the input to the <span>text preparation algorithm</span>.</p></dd>
-->
<dd><p>Use the following process to determine the value for the
<dfn for="CanvasDirection"><code data-x="dom-context-2d-inherited-direction">inherited direction</code></dfn> referred to in the <span>text preparation algorithm</span></p>

<dt><dfn enum-value for="CanvasDirection"><code data-x="dom-context-2d-direction-inherit">inherit</code></dfn>
<ol>
<li><p>If <var>object</var>'s <span>font style source object</span> is a <code>canvas</code>
element:</p>
<ol>
<li><p>If the element has a <span>computed value</span> for
<span>'direction'</span> use that as the <span data-x="dom-context-2d-inherited-direction">inherited direction</span>.</p></li>

<dd><p>Default to the directionality of the <code>canvas</code> element or <code>Document</code>
as appropriate.</p></dd>
<li><p>Otherwise, use the <span data-x="the directionality">directionality</span>
of the element as the <span data-x="dom-context-2d-inherited-direction">inherited direction</span>.</p></li>
</ol>

<li><p>Otherwise, <var>object</var>'s <span>font style source object</span> is an
<code>OffscreenCanvas</code> object. Set the <span
data-x="dom-context-2d-inherited-direction">inherited direction</span> to the
<code>OffscreenCanvas</code>'s internal <span
data-x="offscreencanvas-inherited-direction">inherited
direction</span>.</p></li>
</ol>
</dd>
</dl>

<p>The <code data-x="dom-context-2d-fontKerning">fontKerning</code> attribute's allowed keywords
Expand Down Expand Up @@ -67033,32 +67106,11 @@ worker.postMessage(offscreenCanvas, [offscreenCanvas]);</code></pre>
data-x="dom-context-2d-direction-rtl">rtl</code>"</dt>
<dd>Let <var>direction</var> be '<span data-x="concept-rtl">rtl</span>'.</dd>

<!--
<dt>If the <var>target</var> object's <code
data-x="dom-context-2d-direction">direction</code> attribute has the value "<code
data-x="dom-context-2d-direction-auto">auto</code>"</dt>
<dd>
Find the first character in <var>text</var> of bidirectional character type L, AL, or
R, if any. If such a character is found and it is of bidirectional character type AL or R,
then let <var>direction</var> be '<span data-x="concept-rtl">rtl</span>'; otherwise,
let <var>direction</var> be '<span data-x="concept-rtl">rtl</span>'. <ref>BIDI</ref>
</dd>
-->

<dt>If the <var>target</var> object's <span>font style source object</span> is an
element</dt>

<dd>Let <var>direction</var> be <span>the directionality</span> of the <var>target</var> object's <span>font style source object</span>.</dd>

<dt>If the <var>target</var> object's <span>font style source object</span> is a
<code>Document</code> with a non-null <span>document element</span></dt>

<dd>Let <var>direction</var> be <span>the directionality</span> of the <var>target</var>
object's <span>font style source object</span>'s <span>document element</span>.</dd>

<dt>Otherwise</dt>

<dd>Let <var>direction</var> be '<span data-x="concept-ltr">ltr</span>'.</dd>
data-x="dom-context-2d-direction-inherit">inherit</code>"</dt>
<dd>Let <var>direction</var> be the <var>target</var>'s <span
data-x="dom-context-2d-inherited-direction">inherited direction</span>.</dd>
</dl>
</li>

Expand Down Expand Up @@ -71268,6 +71320,11 @@ interface <dfn interface>OffscreenCanvas</dfn> : <span>EventTarget</span> {
data-x="dom-OffscreenCanvas-height">height</code> attributes of the <code>OffscreenCanvas</code>
object. Initially, all the bitmap's pixels are <span>transparent black</span>.</p>

<p>An <code>OffscreenCanvas</code> object has an internal <dfn
data-x="offscreencanvas-inherited-lang">inherited language</dfn> and <dfn
data-x="offscreencanvas-inherited-direction">inherited direction</dfn> set when
the <code>OffscreenCanvas</code> is created.</p>

<p>An <code>OffscreenCanvas</code> object can have a rendering context bound to it. Initially,
it does not have a bound rendering context. To keep track of whether it has a rendering context
or not, and what kind of rendering context it is, an <code>OffscreenCanvas</code> object also
Expand All @@ -71288,9 +71345,35 @@ interface <dfn interface>OffscreenCanvas</dfn> : <span>EventTarget</span> {
array of <span>transparent black</span> pixels of the dimensions specified by <var>width</var> and
<var>height</var>; and its <code data-x="dom-OffscreenCanvas-width">width</code> and <code
data-x="dom-OffscreenCanvas-height">height</code> attributes initialized to <var>width</var> and
<var>height</var> respectively.</p>
<var>height</var> respectively. The <span data-x="offscreencanvas-inherited-lang">inherited
language</span> and <span data-x="offscreencanvas-inherited-direction">inherited direction</span>
internal values must be set as follows:</p>

<hr>
<ol>
<li><p>Let <var>global</var> be the <code>OffscreenCanvas</code>'s <span>relevant global
object</span>.</p></li>
<li><p>If <var>global</var> is a <code>Window</code> object:</p>
<ol>
<li><p>Let <var>Document</var> be the <var>global</var>'s
<span data-x="concept-document-window">associated <code>Document</code></span>.</p></li>

<li><p>Set the <span data-x="offscreencanvas-inherited-lang">inherited language</span>
to the <var>Document</var>'s <span data-x="language">language</span>.</p></li>

<li><p>Set the <span data-x="offscreencanvas-inherited-direction">inherited direction</span>
to the <var>Document</var>'s <span data-x="the directionality">directionality</span>.</p></li>
</ol>
</li>
<li><p>Otherwise:</p>
<ol>
<li><p>Set the <span data-x="offscreencanvas-inherited-lang">inherited language</span>
to explicitly unknown.</p></li>

<li><p>Set the <span data-x="offscreencanvas-inherited-direction">inherited direction</span>
to "ltr".</p></li>
</ol>
</li>
</ol>

<p><code>OffscreenCanvas</code> objects are <span data-x="transferable
objects">transferable</span>. Their <span>transfer steps</span>, given <var>value</var> and
Expand Down Expand Up @@ -146999,6 +147082,7 @@ INSERT INTERFACES HERE
Ştefan Vargyas,
Stefan Weiss,
Steffen Meschkat,
Stephen Chenney,
Stephen Ma,
Stephen Stewart,
Stephen White,
Expand Down