bug#43405: Tool bar item doesn't align to the right edge

[Eli Zaretskii]

> From: Robert Pluim <rpluim@gmail.com>
> Cc: 43405@debbugs.gnu.org,  juri@linkov.net
> Date: Mon, 21 Sep 2020 22:07:51 +0200
> 
>     Eli> I'd first try to repeat what we do for :align-to support: insert a
>     Eli> stretch glyph of a suitable width, computed using it->last_visible_x
>     Eli> and the width of the image for the button that has to be
>     Eli> right-justified.  See produce_stretch_glyph (except that most of it 
> is
>     Eli> not relevant, since :align-to supports a lot of functionalities).
> 
> OK, that would work, but then you could only right justify a single
> item, which would be different from what you can do with the GTK tool
> bar

No, it will work with more than one as well, you just need to loop
twice over all the buttons and keep track of all those which should be
right-justified.

> (and I see no reason to restrict this to tool bar buttons, I see
> at least org-mode wants to right-justify headline tags)

What are "headline tags" in Org, and how are they related?

Your original description said:

> So let's assume we do this by exending the display spec to allow
> 
> '(:right-justify t)
> 
> which would mean to move everything on this line as far to the right
> in the window as possible.

"Everything on this line" on which line?

Do you mean you want to display an entire screen line justified to the
right?  Then we already do something like that with R2L lines
(although there we also reorder display elements, something you don't
need here).