Fwd: [w3c/wcag] Proposal for color and contrast (1.3.1, 1.4.1, 1.4.3., 1.4.6, 1.4.11) (WCAG 3.0) (#901) from Jim Allan on 2019-09-16 (public-low-vision-a11y-tf@w3.org from September 2019)

From: Jim Allan <jimallan@tsbvi.edu>
Date: Mon, 16 Sep 2019 12:08:56 -0500
To: public-low-vision-a11y-tf <public-low-vision-a11y-tf@w3.org>
Message-ID: <CA+=z1WkPhyhprKicH4-NRXDAT1MUS=sQ=KQ08U9RMqAV__PmYQ@mail.gmail.com>
food for thought...

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From: JAWS-test <notifications@github.com>
Date: Sun, Sep 15, 2019 at 10:52 PM
Subject: [w3c/wcag] Proposal for color and contrast (1.3.1, 1.4.1, 1.4.3.,
1.4.6, 1.4.11) (WCAG 3.0) (#901)
To: w3c/wcag <wcag@noreply.github.com>
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There have been many discussions here about contrasts, which I do not think
have led to a satisfactory outcome (
https://github.com/w3c/wcag/issues?q=is%3Aissue+1.4.11). I am afraid that
the problems with WCAG 2.1 and 2.2 cannot be solved because the SCs are
unchangeable and the "Understanding" documents cannot give the SCs any
other meaning. But I think that for WCAG 3.0 a thorough revision of the
color and contrast themes would be useful.

Unfortunately, I am not an expert in visual perception. However, I suspect
that the following is correct:

   - Currently, color (1.4.1) and contrast requirements (1.4.3, 1.4.6,
   1.4.11) overlap (#201 <https://github.com/w3c/wcag/issues/201>). This
   should be clearly separated.
   - 1.4.11 is missing a level AAA-SC. This should be added.
   - The minimum contrast of distant content is not clearly defined in any
   SC (#875 <https://github.com/w3c/wcag/issues/875>, #873
   <https://github.com/w3c/wcag/issues/873>, #871
   <https://github.com/w3c/wcag/issues/871>). This should be corrected.
   - The legibility does not depend on the font size, but on the line width
   of the letters (i.e. the font-family and font-weight). The line width
   should therefore be taken into account.
   - The detection of contrast distances is no better or worse for text
   than for non-text contents (with the same line width). 1.4.3 and 1.4.11
   should therefore be merged and 1.4.6 supplemented.
   - Detecting small contrast distances between foreground and background
   is easier than detecting small contrast distances between distant elements.
   1.4.11 and 1.4.14 should therefore consider the contrast distance of
   distant content with a higher requirement (no exception from a certain line
   width).
   - With distant elements the line width does not improve the detection of
   contrast distances. Therefore no exception from a certain line width.
   - Disabled items also require minimum contrasts when submitting
   information (#869 <https://github.com/w3c/wcag/issues/869>). This
   restriction should be supplemented in the exception
   - An alternative representation (e.g. text alternative instead of
   diagram) usually means a loss of information or efficiency for impaired
   users. Therefore, it should be avoided (and prohibited at level AAA).
   - The contrast requirements should only apply if the user has not
   adjusted the contrasts. This should be added to the exception for user
   agents in the SC.
   - If the user adjusts the colors or contrasts, he or she should still be
   able to perceive the information transmitted via color or contrasts (#623
   <https://github.com/w3c/wcag/issues/623>). This should be covered by SC
   1.3.1.

Therefore I suggest the following:
Changed SC

   - 1.4.1 Use of color, Level A: Color is not used as the only visual
   means of conveying information.
   - 1.4.3 Contrast between foreground and background (Minimum), Level AA:
   The visual presentation of text, images of text, user interface components
   and graphical objects has a contrast ratio of at least 4.5:1, except for
   the following:
      - Wide line width: Elements with a line width greater than 2px have a
      contrast ratio of at least 3:1.
      - Incidental: Content that is part of an inactive user interface
      component (unless this component transmits information), that is pure
      decoration, that is not visible to anyone, or that is part of a picture
      that contains significant other visual content, has no contrast
requirement.
      - Logotypes: Text and graphical objects that are part of a logo or
      brand name has no contrast requirement.
      - User Agent and User: No contrast requirement if the appearance of
      the content is determined by the user agent or the user and not
modified by
      the author.
      - Alternative presentation: If there is an alternative presentation
      on the page that meets all requirements, then there is no contrast
      requirement.
   - 1.4.6 Contrast between foreground and background (Enhanced), Level
   AAA: The visual presentation of text, images of text, user interface
   components and graphical objects has a contrast ratio of at least 7:1,
   except for the following:
      - Wide line width: Elements with a line width greater than 2px have a
      contrast ratio of at least 4.5:1.
      - Incidental: Content that is part of an inactive user interface
      component (unless this component transmits information), that is pure
      decoration, that is not visible to anyone, or that is part of a picture
      that contains significant other visual content, has no contrast
requirement.
      - Logotypes: Text and graphical objects that are part of a logo or
      brand name has no contrast requirement.
      - User Agent and User: No contrast requirement if the appearance of
      the content is determined by the user agent or the user and not
modified by
      the author.
   - 1.4.11 Contrast between distant content, Level AA (Minimum): If color
   between distant contents (text, images of text, user interface components
   and graphical objects) is only visual means to communicate the status or
   role of the contents, the contrast ratio must be at least 4,5:1, except for
   the following:
      - Incidental: Content that is part of an inactive user interface
      component (unless this component transmits information), that is pure
      decoration, that is not visible to anyone, or that is part of a picture
      that contains significant other visual content, has no contrast
requirement.
      - Logotypes: Text and graphical objects that are part of a logo or
      brand name has no contrast requirement.
      - User Agent and User: No contrast requirement if the appearance of
      the content is determined by the user agent or the user and not
modified by
      the author.
      - Alternative presentation: If there is an alternative presentation
      on the page that meets all requirements, then there is no contrast
      requirement.
   - 1.4.14 Contrast between distant content, Level AAA (Enhanced): If
   color between distant contents (text, images of text, user interface
   components and graphical objects) is only visual means to communicate the
   status or role of the contents, the contrast ratio must be at least 7:1,
   except for the following:
      - Incidental: Content that is part of an inactive user interface
      component (unless this component transmits information), that is pure
      decoration, that is not visible to anyone, or that is part of a picture
      that contains significant other visual content, has no contrast
requirement.
      - Logotypes: Text and graphical objects that are part of a logo or
      brand name has no contrast requirement.
      - User Agent and User: No contrast requirement if the appearance of
      the content is determined by the user agent or the user and not
modified by
      the author.

Note for 1.4.1, 1.4.3, 1.4.6, 1.4.11:
This success criterion deals specifically with the perception of
color/contrast in the standard display of the page. Other forms of
perception are covered in SC 1.3.1 including programmatic access to
information transmitted via color/contrast and other visual presentation
coding.
Understanding

1.3.1 also applies to users who adapt color and contrasts (user styles,
adaptation of colours in the browser, high contrast mode etc.). This means
that the following must be fulfilled for information transmitted via color
or contrast:

   - text alternative,
   - other visual means (which are not based on color and contrast) or
   - programmatic access to color and contrast supported by assistive
   technologies (e.g. ARIA attributes are not recognized and therefore do not
   fulfill SC 1.3.1 for visually impaired people)

1.4.1 applies only to colors that transmit information as a specific color
and are therefore not interchangeable (e.g. red = error, green = success).
If the color is interchangeable with any other color, 1.4.1 is not
applicable. Then only the contrast requirements from 1.4.3, 1.4.6, 1.4.11,
1.4.14 apply.

1.4.3, 1.4.6

   - The line width of 2px corresponds approximately to the previous font
   size definition (14pt and 18pt).
   - In order to determine the line width, the thinnest part is used whose
   perceptibility is relevant (for letters, for example, not the serifs).

1.4.11, 1.4.14 applies for example for:

   - focused,
   - hovered,
   - deactivated,
   - selected,
   - checked,
   - faulty,
   - correct,
   - content type

Relevant in this context

   - Note 4 in definition "contrast ratio" still relevant? #876
   <https://github.com/w3c/wcag/issues/876>
   - Non-sRGB color spaces, outdated sRGB threshold, and other issues in
   the "relative luminance" definition: #360
   <https://github.com/w3c/wcag/issues/360>

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-- 
Jim Allan, Accessibility Coordinator
Texas School for the Blind and Visually Impaired
1100 W. 45th St., Austin, Texas 78756
voice 512.206.9315    fax: 512.206.9452 http://www.tsbvi.edu/
"We shape our tools and thereafter our tools shape us." McLuhan, 1964
Received on Monday, 16 September 2019 17:08:04 UTC