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readium / readium-css

šŸŒˆ A set of reference stylesheets for EPUB Reading Systems, starting with Readium Mobile
https://readium.org/readium-css/
BSD 3-Clause "New" or "Revised" License
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CSS HTML5 patch causes some digits to descent from baseline #124

Closed danielweck closed 5 months ago

danielweck commented 1 year ago

Original issue reported in Thorium's GitHub repository by @civodulab

https://github.com/edrlab/thorium-reader/issues/1936

danielweck commented 1 year ago

Sorry for the multiple posts, the GitHub API is experiencing problems: https://www.githubstatus.com

So, the bug is that Readium CSS sets font-variant-numeric: oldstyle-nums proportional-nums; on the body element:

https://github.com/readium/readium-css/blob/583011453612e6f695056ab6c086a2c4f4cac9c0/css/src/modules/ReadiumCSS-html5patch.css#L59

gautierchomel commented 1 year ago

Readium CSS forces old style numbers. This happens if they exists in the font set. One will consider it a bug while others will consider it's a feature.

It might be addressed thru documentation as a publisher can override it by setting aligned numbers with font-variant-numeric: normal;.

JayPanoz commented 5 months ago

What @gautierchomel explained. Thatā€™s more or less a ā€œbest typography practiceā€ for body copy.

It should at least be disabled when applying one of the a11y typefaces or forcing the a11y normalisation, to confirm Gautierā€™s snippet of CSS.

https://github.com/readium/readium-css/blob/583011453612e6f695056ab6c086a2c4f4cac9c0/css/src/modules/user-settings-submodules/ReadiumCSS-a11yFont_pref.css#L44-L51

JayPanoz commented 5 months ago

Alright so this is a feature and not a bug, and actually also an attempt at normalising numerals for body composition since there is no guarantee fonts ship with oldstyle or lining by default, normal is up to the typefacesā€™ designer ā€“ e.g. Times New Roman comes with lining numerals while Georgia comes with oldstyle on MacOS, when nothing is applied.

So thereā€™s not much to fix there, but maybe a feature request to make for a dedicated setting. Iā€™m not sure it can be useful, especially as there is no guarantee both variants are included with every set of fonts, so users could also possibly find themselves with a setting that doesnā€™t visibly work while the issue is the font not having either lining or oldstyle variants.

Closing, but feel free to re-open another issue for that.