Re: How to measure frame rate in fps?

[Eli Zaretskii <eliz@gnu.org>]

> Cc: wyuenho@gmail.com, emacs-devel@gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Tue, 1 Jun 2021 18:00:35 +0300
> 
> > I also am not sure the above faithfully reflects what happens in Real
> > Life when Emacs has nothing to redisplay: I think you get the tool-bar
> > redisplay triggered because the evaluation of the benchmark call
> > causes it somehow.  How did you evaluate it, exactly?
> 
> Either using M-:, or with M-x benchmark like you suggested (only without 
> prefix argument, to measure just 1 iteration). The results are similar.

Yes, that figures: entering the minibuffer triggers a more thorough
redisplay than usual: we redisplay the menu bar, the tool bar, and
several other things as result, for reasons that should be obvious.

Try C-x C-e instead after typing the sexp in *scratch.  In that
scenario, I don't expect the tool bar to be redrawn.

> > How do you deduce that posn-at-point triggers redisplay of the GTK
> > tool bar?  It shouldn't, AFAIR.  posn-at-point and its ilk only
> > simulate display of text, they don't care about window's and frame's
> > decorations.
> 
> You're right, posn-at-point shows me different timings. Often enough as 
> high as 12-15ms, which is not great for a low latency display, but the 
> numbers don't seem to be tied to tool-bar-mode being on.

If you want me to take a look at those 15ms cases, I suggest to file a
bug report with the details and a recipe.