bug#30746: window-text-pixel-width includes width of following propertized space

[Eli Zaretskii]

> From: Clément Pit-Claudel <clement.pitclaudel@live.com>
> Date: Wed, 7 Mar 2018 17:13:32 -0500
> 
> (progn
>   (save-excursion
>     (insert #("s " 1 2 (display (space :width (50))))))
>   (window-text-pixel-size nil (point) (1+ (point))))
> 
> On my machine a single 's' is 8 pixels wide, but this snippet returns 58.  
> 
> The following snippet, however, returns 8 as expected:
> 
> (progn
>   (save-excursion
>     (insert "s "))
>   (window-text-pixel-size nil (point) (1+ (point))))
> 
> It seems that adding a display property on the space changes the return value 
> of window-text-pixel-size; is that expected?

It's expected given the relatively naïve implementation, which didn't
expect such calamities.  Hopefully now fixed on the master branch.