bug#56323: 29.0.50; [v2] Add new customisable phonetic Tamil input method

[Visuwesh]

[வெள்ளி ஜூலை 01, 2022] Eli Zaretskii wrote:

>> > Looks like simple misalignment to me, which should be cured by using
>> > pixel-resolution alignment features.
>> 
>> Yep, it is misalignment.  I could try to use those pixel-resolution
>> alignment features but I really don't think I can do a good enough job.
>> It is something I tried in the past but gave up since it was too complex
>> for me.  The current code produces a Good Enough™ table and I think I
>> will just leave it unless Someone™ complains since after all, the
>> current situation is much better than what we have in Emacs 28 (the
>> docfix that happened as part of bug#50143 isn't in Emacs 28).
>
> I thought vtable.el was about solving such problems?

I tried to use vtable.el to produce the syllable table.  There are two
problems:

    . all the calculation done by vtable is slow (perhaps to no one's
      surprise).
    . the buffer becomes noticeably slow to scroll after the table is
      inserted.

I've attached an elisp file of my current progress.

table.el
Description: application/emacs-lisp

When I commented out the make-vtable call and benchmarked it, it was
fast so it is not the creation of table data structure that is the
bottleneck.