Re: Is it ok to use (redisplay), or should this be left to the experts?

[Eli Zaretskii <eliz@gnu.org>]

> From: Joost Kremers <joostkremers@fastmail.fm>
> Date: Thu, 10 Jan 2019 21:43:44 +0100
> 
> The problem is that although full screen is activated before 
> calculating the text width, (window-total-width) still reports the 
> window width that existed before full screen was activated. This 
> seems to be some sort of race condition, because adding (sleep-for 
> 2) before calling (window-total-width) solves the issue.

Does (sit-for 0) also solve the issue?  If not, try values of argument
smaller than a second, starting from, say, 0.02, and see if some small
enough value resolves the problem.

> It seems that a call to (redisplay) also does the trick, but I'm 
> hesitant to add this, because, well, I'm not sure why, exactly, 
> it's just that I'm not entirely sure when, i.e., in what 
> circumstances, (redisplay) is meant to be used, what side effects 
> to watch out for (in any), etc.

There should be no problem with invoking 'redisplay', it just slows
down the program a bit, especially if the code in question will or
might be executed frequently.  However, sit-for is IMO better, because
in some use cases you must allow for the window manager to respond to
the full-screen request and for Emacs to receive a notification from
the window manager.  And that means waiting for some short time.

> So I guess what I'm asking is whether someone can tell me whether 
> (redisplay) is the right way to deal with this issue, or whether 
> there is a better way. Or perhaps the user is SOL and needs to do 
> some local configuration to get things to behave?

I cannot answer this because it isn't clear to me who initiated
full-screen: the user or the package.  If it's the package, then the
package should also accommodate these issues, perhaps only when the
frame size changes significantly.