Quoting WCAG 2.2 "Success Criterion 1.4.3 Contrast (Minimum)" [1]:
> The visual presentation of text and images of text has a contrast
> ratio of at least 4.5:1, except for the following:
>
> Large Text
>
> Large-scale text and images of large-scale text have a contrast
> ratio of at least 3:1;
Regarding large text, the corresponding "Understanding SC 1.4.3" [2]
clarifies:
> Text that is larger and has wider character strokes is easier to read at
> lower contrast. The contrast requirement for larger text is therefore
> lower. This allows authors to use a wider range of color choices for
> large text, which is helpful for design of pages, particularly titles.
> 18 point text or 14 point bold text is judged to be large enough to
> require a lower contrast ratio.
Therefore, lower the text contrast requirement in
Writer's accessibility check from 4.5 to 3.0 for
text that is considered large according to that
specification.
Add a unit test with 2 test documents:
* one that adheres to the requirements and would have triggered false
positives without this change in place
(sw/qa/core/accessibilitycheck/data/ContrastTestOK.odt)
* one that doesn't adhere to the requirements and still fails the
check, as it should
(sw/qa/core/accessibilitycheck/data/ContrastTestFail.odt)
[1] https://www.w3.org/TR/WCAG22/#contrast-minimum
[2] https://www.w3.org/WAI/WCAG22/Understanding/contrast-minimum.html
Change-Id: I398f72aa5bdcd77c42834632575d6465a5ecd586
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/178127
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>
Tested-by: Jenkins
Reviewed-by: Balazs Varga <balazs.varga.extern@allotropia.de>
a4b03fce93