bug#20180: Missing documentation about redisplay.

[Eli Zaretskii]

> Date: Mon, 23 Mar 2015 16:08:50 +0000
> From: Alan Mackenzie <acm@muc.de>
> 
> The elisp manual doesn't contain adequate documentation about
> (re)display.
> 
> The topics not covered include

They include much more.  Describing the display engine to any depth is
a research project, not a bug report.  Maybe if you had more specific
questions, they could be answered.

The closest thing to what you are asking for is in the large
commentary at the beginning of xdisp.c.

> 1. What triggers redisplay.

See below: this is already covered.

> 2. What portions of the frame/all frames get redisplayed when a
>   redisplay occurs, and how does this relate to the answer to 1..
> 
> There is a partial answer to 1. on the page "Forcing Redisplay" which
> states that "Emacs normally tries to redisplay the screen whenever it
> waits for input.", but this is clearly incomplete - redisplay also
> happens in the absence of input (e.g. by context fontification).

I don't udnerstand what you are saying here: "waiting for input" and
"there's no input" is not a contradiction, on the contrary: yo uwait
for input when there's none.  And what is "context fontification"?

> One clearly needs an answer to 2. if one ever wants to cause the
> redisplay of a particular part of a window or frame.

To do that, you need to change the text of that part or the text
properties/overlays that affect how that part looks on display.  But
you most probably already know that, so I'm again not sure what the
question is.