Subject: bug#61667: 29.0.60; Failure to redisplay

From: Dmitry Gutov <[email-masked]>
Date: Sun, 26 Feb 2023 13:59:34 +0200

On 26/02/2023 08:44, Eli Zaretskii wrote:
> Sorry, I'm still confused.  Let me try to explain what I understand
> and what confuses me.
> 
> There are two use cases where you see the problem:
> 
>    . "emacs -Q", then type 'a' (which visits a file?)
>    . "emacs" with your configuration, then type "C-x b", which visits a
>      file
> 
> In both cases, you see a delay before the display is updated, right?

About 1 in 5-10 tries the delay is high enough to be noticeable 
(200-300ms with -Q and up to 1-2 seconds with my config).

> So what effect, if any, does the changing vs fixed frame title have on
> each of these two use cases?

The delay (which is, physically, always present) becomes never nigh 
enough to be noticeable.

Or, in simple terms, disappears.

> And what effect does disabling
> double-buffering have on each of these two cases?

Same effect: delay "disappears".

> AFAIR, you originally said that when the title is not updated, the
> problem disappears.

Yes.

> Then you said that the problem does NOT disappear
> when the title is fixed, but having the title change makes it easier
> to realize that the delay exists.

I only said (or meant to say) that having the title change made it 
easier to understand that there definitely *is* a problem. Because 
otherwise I could attribute the delay to various sources of latency we 
could experience: reading from disk (or network, whatever), triggering a 
garbage collection, etc. But since the title changes, the buffer must 
already be read and visited, and yet it's not displayed in the frame for 
some time.

> Now you are saying something else.
> This is what confuses me: what is the effect of the changing frame
> title on the above two cases?

Delay disappears.