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Call for Consensus (CfC): APA Comment on CSS Color Module Level 5

From: Matthew Atkinson <matkinson@tpgi.com>
Date: Wed, 17 Aug 2022 11:40:12 +0000
To: "public-apa-admin@w3.org" <public-apa-admin@w3.org>
Message-ID: <AD39CD8B-656D-4608-9791-B7D7566E4389@tpgi.com>
Colleagues: This is a Call for Consensus (CfC) to the Accessible Platform Architectures (APA) Working Group testing for agreement on a formal comment on the CSS Color Module Level 5 specification (https://www.w3.org/TR/2022/WD-css-color-5-20220628/).

An accessibility review was requested of the APA as part of our role in performing horizontal review of W3C documents for accessibility concerns.

It was reviewed by APA member Matthew who proposed the comments you can find below. I have made some minor edits for clarity, and to reflect it's a group comment. Please note that these take into account the discussion we had about noting trigger warnings in color names, should a specific palette be used as the basis for creating descriptive color names: https://www.w3.org/2022/08/10-apa-minutes.html#t10

If the group agrees, the main review comment will be posted on the thread where the review was requested (https://github.com/w3c/a11y-request/issues/29) and the rest of the comments, about the document's accessibility, will be posted on the CSS Working Group's issue tracker, as a series of separate, specific issues (which will all be noted as being on the behalf of APA). Non-substantive edits will be made in order to allow the issues to stand alone. (https://github.com/w3c/csswg-drafts/issues/)

*** Action to Take ***

This CfC is now open for objection, comment, as well as statements of support via email. Silence will be interpreted as support, though messages of support are certainly welcome.

If you object to this proposed action, or have comments concerning this proposal, please respond by replying on list to this message no later than 23:59 (Midnight) Boston Time, Wednesday 24 August.

NOTE: This Call for Consensus is being conducted in accordance with the APA Decision Policy published at: http://www.w3.org/WAI/APA/decision-policy

<APA Comments>

# Overall accessibility review comment

APA has no accessibility concerns regarding the substance of [CSS Color Module Level 5](https://www.w3.org/TR/2022/WD-css-color-5-20220628/) (we reviewed the 2022-06-28 WD).

It's clear that a lot of effort has gone into making the document readable and understandable. However, we did notice some accessibility barriers, particularly from the perspective of readers who may struggle with color perception. These concerns, with suggestions, are being filed as issues on the CSSWG tracker.

We're aware that `color-contrast()` has been pushed back to Level 6. However, we were wondering what are the use cases for this function? The function selects from a pre-determined list of colours; are there situations in which the answer could not have been determined at design time? We don't feel that this function is required in order to further accessibility, but we're happy to provide any needed support in adding it, if you wish to add it or something similar in future.

# Accessibility suggestions on the document's presentation

## General: color previews

### Naming colors

Adding "alternative text" to the visual color preview feature could be very helpful for people with vision impairments who currently have to rely on the colors' coordinates alone. Whilst coordinates are provided for every color mentioned in the examples, they may not give the reader much of a sense of what the color might look like, making the examples hard to follow (e.g. it's much easier to understand the effects of certain types of mixing by glancing at the previews and noting the similarities or differences from the input colors, rather than parsing through the coordinates). The document describes some of the colors that have previews, but not all.

There are some tools that gives you the closest color name to a given (usually hex-encoded) color, from an extensive palette of predefined colors. This sort of tool would give a good enough idea for most people who may be unable to perceive the colors directly. The color names could be generated as part of the document build process, and placed in visually-hidden text in the document. The text should also indicate if the colours are transparent.

One such tool is "color-to-name" (<https://github.com/stanleyfok/color-to-name>)—however, a small number of the color names in the palette may be considered vulgar, so they would either have to be filtered out, or a different tool selected. The same applies for color names that may be triggering for some people. We can do more research on tools of this nature, if you like.

It's noted that out-of-gamut colors are indicated by a red border on their previews, and they're always described in accompanying text as being out of gamut, which is helpful.

### Keyboard operability for the previews

The color previews can be hovered with the mouse. When this happens, they enlarge, covering some of the text behind. This is particularly useful if the preview is of a transparent color, as the text behind shows through the preview window. It is not possible to activate the preview with the keyboard, so keyboard-only users would likely miss out on this helpful feature.

### Previews in `<pre>` blocks—rendering bug

The previews inside code example blocks can't expand outside of those blocks, so aren't drawn fully in those cases.

## General: Test result indication

_This is quite possibly a bug in a library you're using, though I couldn't find any pointers after a brief search relating to WPT._

There's a low contrast difference between the two sections of the pie charts. This is particularly apparent in §4.

Suggestion: use techniques similar to those from [Figure 21 in the Understanding WCAG SC 1.4.11 document](https://www.w3.org/WAI/WCAG21/Understanding/non-text-contrast.html#figure-passing-pie-chart), i.e. (1) separating the segments; (2) using more contrasting colours; and/or (3) using hollow and solid segments to ease differentiation.

## §2.2

### Example 2

* This example has a figure with a descriptive caption. The `<img>` element lacks an `alt` attribute. The `alt` text should mention that the image shows three colours (the two inputs, and the mixed output) on a plane with two axes. The axes are labelled "a" and "b" and cross at the origin, which is in the centre of the plot. We are looking down the L axis onto an ab plane.
* An `<img>` that has `alt` text in Example 22 (in §3.6) refers to this plane as the CH plane. This seems to be conventional, but it may be helpful for people who are not familiar with color spaces to mention it in the document's text.
* For someone who struggles to see the color, or low-contrast colors, it would be helpful to label the colors on the chart ("peru", "palegoldenrod" and "mixed" for the mixed color, in this case). (You could perhaps do this with numbers, to save space, and keep the layout simple, in the diagram, as long as they match up to numbers, color previews, and coordinates in the text below.)

### Example 3

The above three issues apply here too.

## §3.6

### Example 22

In the spirit of the issue reported above, we don't feel this needs extensive `alt` text (though describing the axes and general situation would be helpful). However, it would be particularly helpful to ensure that the different colors can be identified on the plot, e.g. via labelling.

## §4.4

### Figure 5

* The `<img>` needs `alt` text such as "A color swatch, in a grid layout".
* The second part is marked up as a `<table>` but doesn't seem to be one semantically (it's just placing the text to match the layout of the color swatch above). Suggest applying `role="presentation"` to the table, to remove the tabular structure semantics (or you could re-code it using `<div>`s and `<span>`s). That would have the effect of linearizing the table from a screen reader perspective, but that would likely be less confusing than encountering a "table" without headers.

### Example 33

Color previews are missing.

## §5

### Figure 6

* The `<img>` needs an `alt` attribute that explains this is a color swatch in a grid formation (as per figure 5) but that circles are imposed on each grid square. The `<figcaption>` does a great job of explaining the rest.
* As with figure 5, this table should have the table semantics removed (or be re-coded using `<div>`s and `<span>`s).

</APA Comments>

Matthew Tylee Atkinson (he/him)
Principal Accessibility Engineer
TPG Interactive

A Vispero Company

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