Then can we do something like
  (set-fontset-font "fontset-default" '(#x11FC0 . #x11FFF)
                    '("Noto Sans Tamil Supplement" . "iso10646-1") nil
'prepend)

in lisp/international/fontset.el?
After doing this both the "base" and supplement characters are being
displayed correctly.

On Wed, Jun 1, 2022 at 11:09 PM Eli Zaretskii <eliz@gnu.org> wrote:

> > From: समीर सिंह Sameer Singh <lumarzeli30@gmail.com>
> > Date: Wed, 1 Jun 2022 22:25:52 +0530
> > Cc: Eli Zaretskii <eliz@gnu.org>, emacs-devel@gnu.org
> >
> >  This is a sub-optimal solution IMHO.  There will always be cases where
> >  a script is split into multiple Unicode blocks, probably mapped to
> >  different fonts.  AFAICS, the Tamil supplement characters don't
> >  interact typographically with normal Tamil characters, so a two-font
> >  solution in this case is valid.  In case my assumption is invalid you
> >  should submit a bug to the Noto project :-)
> >
> > I agree it is somewhat sub optimal, but Emacs does not differentiate
> between supplement and "base"
> > characters, so setting different fonts for both of them does not seem
> possible.
>
> Of course, it's possible: set-fontset-font can accept ranges of
> codepoints and use different font for each range.  It doesn't have to
> accept only script names.
>
> > There also seems to be no font which supports both Tamil and its
> supplement characters OOTB.
>
> That part is indeed sub-optimal, but not a catastrophe if they are
> displayed independently, i.e. there are no composition rules that
> cross the boundary between the blocks.
>