Re: How to record the line number pixel width for each window.

[Eli Zaretskii]

> Cc: "address@hidden" <address@hidden>
> From: Keith David Bershatsky <address@hidden>
> Date: Fri, 6 Dec 2019 11:29:04 -0800
> 
> By "simulate", I had in mind actively using the move_it family of functions 
> -- where Emacs inhibits updating the glass and we can navigate the text to 
> ascertain and/ or set certain values.  For example, the sample snippet/diff 
> in the opening post of this thread occurs when Emacs is using IT to set the 
> value of the line number pixel width, and this is happening in the context of 
> what I think of as a redisplay simulation.  The solution to my issue may be 
> as simple as devising a condition limiting just when to set the window object 
> with the line number pixel width; e.g., when IT is on the first visible line 
> of text in the window (following the header line, if any).  Right now, the 
> snippet sets the value when IT is on other lines besides the first line of 
> text in the window, perhaps even a hidden / invisible line due to folded 
> text.  Perhaps that folded / invisible line would have a different line 
> number pixel width, but it is not used because it is hidden and the value is 
> erroneous.

I don't have any specific advice for you.  In general, the required
width of the line-number display is calculated when a window's
redisplay starts, the first time display_line is called for that
window's text area.  In some rare cases, displaying subsequent lines
comes up with a larger value (as can be seen in Org mode with many
folded line).  So maybe looking at the last value in a window will do
what you want.

Again, I don't recommend this approach, as it is fundamentally wrong
IMO.