Bug 233447 – Consonant clusters with a visible virama should only have the first consonant+virama highlighted

• Component: Layout and Rendering
• Status: NEW

[r12a]

When the start of a line contains a 2-consonant cluster that uses a *visible* virama, ::first-letter should highlight only the first consonant+virama. This corresponds to a grapheme cluster, as defined by Unicode.

Tests & results:
Interactive test, When ::first-letter is applied to Devanagari the browser will NOT select a 2-consonant cluster as a unit if the virama is visible
https://github.com/w3c/line_paragraph_tests/issues/68

Interactive test, When ::first-letter is applied to Bengali the browser will only select the first consonant+virama in a cluster if the virama is visible
https://github.com/w3c/line_paragraph_tests/issues/70

Interactive test: When ::first-letter is applied to Tamil the browser will only select the first consonant+virama in a cluster if the virama is visible	
https://github.com/w3c/line_paragraph_tests/issues/71


For Devanagari and Bengali, Gecko only highlights the initial character+virama, whereas Blink, and Webkit select all clusters as a single unit, whether or not they are conjuncts or are rendered with a visible virama.

For Tamil, all browsers select only the first grapheme cluster (as expected).

WebKit browsers should not select the full consonant cluster if the virama is showing.

[r12a]

For additional background information, see https://www.w3.org/International/questions/qa-indic-graphemes.en

[Radar WebKit Bug Importer]

<rdar://problem/85865506>

[r12a]

There's a bug report for Firefox at https://bugzilla.mozilla.org/show_bug.cgi?id=1742626 which, though not exactly the same problem, contains a lot of useful discussion around the general problem of correctly segmenting clusters with viramas.

[Myles C. Maxfield]

Cool, thanks for the link.