Bangla
For the Bangla or Bengali language, the Harfbuzz renderer in luatex
is recommended. Here is a minimal example:
\documentclass{article}
\usepackage[bangla, provide=*]{babel}
\babelfont{rm}[Renderer=Harfbuzz]{FreeSerif}
\begin{document}
বাংলা ভাষা বিকাশের ইতিহাস ১৩০০ বছর পুরনো। চর্যাপদ এ ভাষার আদি নিদর্শন।
\end{document}
It works with xetex, too, with a similar output, but with this engine
there is no need the set the renderer (it’s always Harfbuzz).
Counters
Although Bangla numerals are best entered directly in its original
form, you may still need some conversion because LaTeX uses internally
the Arabic ones. With luatex there are two ways to map Arabic to
Bangla numerals, passed as option to \babelprovide:
maparabicdoes it at the TeX level, by redefining\arabic. Note the form written to the auxiliary files is the converted one (which can be an issue in indexes). It works withxetex, too.mapdigitsdoes it at the engine level. This is usually the preferred method.
To perform this conversión, use the following preamble:
\usepackage[bangla, provide=*]{babel}
\babelprovide[mapdigits]{bangla} % or alternatively maparabic
\babelfont{rm}[Renderer=Harfbuzz]{FreeSerif}
There is an additional counter:
alphabetic▸ ক খ গ ঘ ঙ চ ছ জ ঝ ঞ ট ঠ ড ঢ ণ ত থ দ ধ ন প ফ ব ভ
See the explanation in the babel manual about \localecounter and
localenumeral.
Punctuation
Only luatex. The transform danda.nobreak prevents a line break
before a danda or double danda if there is a space.
In Unicode, danda and double danda are shared by several scripts, and
babel doesn’t assign them by default to any of them. If you are using
onchar to select the font you may want to assign them with:
\babelcharproperty{`।}{locale}{bangla}
\babelcharproperty{`॥}{locale}{bangla}