bug#38807: [Feature request]: Support lisp workers like web workers.

[Eli Zaretskii]

> Date: Wed, 1 Jan 2020 11:47:49 +0800
> From: HaiJun Zhang <netjune@outlook.com>
> Cc: "38807@debbugs.gnu.org" <38807@debbugs.gnu.org>
> 
> My understanding of the display flow:
> 1. an event comes which causes redisplay

More often than not, it is not an event, but a command that changes
Lisp data (buffer text, overlays, text properties, position of point,
new or deleted windows, etc.).

> 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.