Dutch IJ not selected as a single grapheme by ::first-letter

[r12a]

When 'IJ' appear together at the beginning of a paragraph (eg. in IJzertoren is een toren en vredes­monument in de West-Vlaamse stad Diksmuide.), both the first two letters should be highlighted.

On the other hand, 'Ij' should not be converted to 'IJ', if it occurs, since it may relate to (rare) nouns such as Ijad, Ijara, Ijaw, Ijaz, Ijebu, Ijenda, Ijeoma, Ijewere, Ijima, Ijja, Ijlal, Ijo, Ijobalit, Ijumaa and probably others. (see w3c/line_paragraph_tests#56 (comment))

This should only work if the language of the text is set to Dutch.

The Gap:

Even with the language of the text set to Dutch, neither Blink nor Webkit select 'ij' or 'IJ' together.

This has been fixed, however, for Gecko if the language of the content is set to Dutch.

However, Gecko also selects 'Ij', which is not correct.

Priority:

This is a Basic error for Dutch users, and needs to be fixed.

Tests & results:

Interactive test Dutch IJ are selected as a single grapheme by ::first-letter

Interactive test Ij is non ambiguously not Dutch IJ nor Dutch ij and should not be selected as a single grapheme for ::first-letter.

Spec status:

The CSS specification specifically mentions that the IJ combination should be treated as a single letter.

Action taken:

Blink • Webkit • Gecko

Outcomes

Gecko fixed selection of 'ij' and 'IJ', if the language of the content is set to Dutch.

[r12a]

The first comment in this issue contains text that will automatically appear in one or more gap-analysis documents as a subsection with the same title as this issue. Any edits made to that comment will be immediately available in the document. Proposals for changes or discussion of the content can be made in comments below this point.

Relevant gap analysis documents include:
Dutch

[r12a]

Edited to reflect that Gecko does support this now. (Try Firefox 90 or later.)

[r12a]

Pointed to bug reports. Existing one for Blink. New one for Webkit.