>
>  2. the display engine prepares the glyph matrix
>  3. convert the glyph matrix to bitmap and display it
>
>  I think lots of work are in 2.
>
>  Actually, 3 is also a lot of work.
>
> Then 3 can be done in a separate thread from 2 and 1?

> How would that help?  Until 3 is done, the user doesn't see the

Couldn't prepare and converting to bitmap, inclusive rendering the bitmap bo done in a separate thread from displaying the same?

Of course, displaying can not be done until previous work has finished, so I don't know if Emacs could interleave the work with something else useful?