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

[Juri Linkov]

> I think you forget how the tool bar is displayed.  In the versions of
> Emacs that produce our native tool bar, the tool bar is displayed by
> displaying a Lisp string made of spaces, where each space has a
> display property which specifies the icon to display.  Your code puts
> the :align-to properties on menu item's name, but that name is not
> used at all for the display of tool bar, so it has no effect.  What
> you need is to put the :align-to property on the respective space of
> the Lisp string used to display the tool bar.  I don't think this can
> be done in Lisp, we need support on the C level.

Actually, I didn't forget how the tool bar is displayed, but hoped
that maybe somehow this is still possible.

> In the versions of Emacs that use the so-called "external tool bar",
> like the GTK build, I don't see how :align-to can have any effect at
> all; we need instead to use GTK facilities to arrange the buttons
> (assuming that such facilities exist and are available to Emacs).

AFAIK, the GTK build supports 4 positions of the tool-bar:
'top', 'bottom' 'left', 'right'.  I can't imagine how the
Hamburger menu icon should be aligned for a tool-bar position
different from the default 'top'.