1309155 - Support complex text layout in the findbar modal highlighting mode

Status: NEW

(Toolkit :: Find Toolbar, defect)

Description

[Mike de Boer [:mikedeboer]]

Currently, the highlighter implementation extracts the matched substring and inserts it into the yellow highlight box.
This usually works fine, except for ligatures and other types of complex text structures that look and mean different things when characters and/or sentences are combined.
https://bugzilla.mozilla.org/show_bug.cgi?id=1279843#c38 lists a few examples, which I'll put here too:

* https://pnb.wikipedia.org/wiki/%D8%B9%D8%B1%D8%A8%DB%8C search for ی
* https://sa.wikipedia.org/wiki/%E0%A4%AD%E0%A4%BE%E0%A4%B0%E0%A4%A4%E0%A5%80%E0%A4%AF%E0%A4%B2%E0%A4%BF%E0%A4%AA%E0%A4%AF%E0%A4%83 search for र (the 27th match seems especially interesting)
* Old Mongolian script - http://www.babelstone.co.uk/Test/Mongolian.html

There are more examples available at https://en.wikipedia.org/wiki/Complex_text_layout.

We'll need at least bug 1282752 fixed (adding a platform API).