Text style readable (enhanced)

Rather than write separate prose for each level, build a text visibility tool that takes font, size, type, stem and height into account and returns a linear research-based score; point it at any text and pass above X. Proposes a different X for running text, which the eye must read at speed as it passes over the line, than for menus, buttons and other short strings where the user dwells on a word. He did not address the enhanced level as such; on this approach enhanced would be a higher number on the same scale. He offers to have the tool built — but only if someone supplies the research and the interaction effects, which he asked sdw32 for directly.

Because font-size and the labels normal and bold mean substantially different things across families, the APC-RC guidelines set silver and gold levels using reference fonts that a designer matches their own typeface against, a one-time exercise per font. His acuity-reserve table, which does not mention an enhanced level, runs in small steps: 0.18 degrees, an 8.3px x-height or a 16px font at Helvetica's 0.52 ratio, is content minimum at critical size, 0.2 degrees (9.4px x-height, 18px font) is the figure for columns and blocks, and 0.24 degrees (11px x-height, 21.5px font) is preferred body. He also insists a practical standard must not demand that everything in a view hit critical values, since spot text such as a copyright bug and sub-fluent text such as captions exist deliberately to keep the visual hierarchy readable.

He points to EN 301 549, which has a two-level shape: an 8 CSS px x-height as best practice for text that can be zoomed, against a 16 CSS px x-height for text and images of text necessary for functionality that is closed to text enlargement. His glance-readability study — roughly 40 participants, random three- and four-letter words at 300 ms, across Open Sans Light through Extra Bold and APCA 30 to 75 — found Open Sans Extra Bold at APCA 30 outperforming Open Sans Light at APCA 75, so the minimum appropriate font size depends on the interaction of weight and APCA contrast, and a single contrast threshold applied across all weights is not fit for purpose. For weight he proposes Wilkins' pixel-density measure (rasterise the alphabet, crop to the x-height, threshold at RGB 128, count black pixels), giving Open Sans Light 20.2 percent, regular 30.7, semibold 40.0, bold 47.5 and extrabold 56.4 — which would turn the regular-to-semibold Open Sans body-text band, from text he wrote for the non-digital standard interpreting the European Accessibility Act, into a testable range.

patrickhlauke lists the rendering variation that makes nominal size and weight values unreliable to test: OS antialiasing, font fallback and substitution, different cuts of the same typeface with subtly different metrics, and browser rendering that made fonts on macOS visually fatter than on Windows. scottaohara adds that CSS scaling can change the rendered size while the specified font-size stays exactly as authored, so the declared value is not the tested value. TestPartners notes that weight 600 is very common and looks bold while strictly not being bold, so any level that keeps the binary normal/bold split has to say how intermediate values are treated. patrickhlauke supports building GreggVan's tool but treats these as the caveats it must carry.

The enhanced level is currently stricter by banning things — no underlining, no decorative or cursive face. In #266 detlevhfischer called the decorative-or-cursive wording too restrictive as a general rule, and Myndex agreed and called it subjective, ambiguous and arbitrary (the same objection recorded against the minimum); neither commented on underlining, and detlevhfischer did not comment on the alternative. Myndex's counter-proposal reshapes what enhanced would mean: require that a plain accessible font is offered as a fallback and that layout features keep working when the user selects it, ideally through a new prefers-font-family: plain media query. The argument is that a stricter author prohibition is the wrong instrument for a dynamic medium where user personalisation can do the work, especially as these voluntary guidelines are being pressed into law.

In #641, a voice recognition software user points out the asymmetry directly: the minimum permits some underlining and the enhanced requirement does not. Having repeatedly tried to open a link that turned out to be randomly underlined text, they want underlining restricted to links at the minimum level — which would collapse the distinction between the two levels on this point rather than preserve it. They argue underlining is a holdover from handwriting, and that digital text has bold and italic for emphasis while underlining has become the convention for links.