Re: animate incredibly slow compared to 21.3

[Richard Stallman]

    To make reliable judgement about the display state, line-move must 
    call sit-for which does redisplay.

That is a really bad problem.  We need to redesign this.
In the past, functions such as compute-motion did the job.
But they have not yet been upgraded to handle computations
involving variabled width fonts, images, etc.

That has been in etc/TODO for many years, but nobody has done
it.  We need this!