bug#28605: 26.0.60; Part of leftmost character hidden

[martin rudalics]

> This works for me:
>
> @@ -3883,7 +3883,7 @@ xg_update_scrollbar_pos (struct frame *f,
>         top /= scale;
>         left /= scale;
>         height /= scale;
> -      left -= (scale - 1) * ((width / scale) >> 1);
> +      width /= scale;

Deceptively simple.  Whatever was that left rigmarole needed for?
What changes with

      width /= scale;
      left -= (scale - 1) * (width >> 1);

> The horizontal scroll bars are still no-show.

With scaling on their positions are apparently off-window.  Some
clearing effect is visible in horizontal-still-not-ok.png but might be
off as well.

> As a funny side effect, each time I turn vertical scrollbars on or off
> (not switching sides) the frame shrinks with about two lines.

This would be too strange.  I suppose it comes from turning on and off
_horizontal_ scroll bars.  Just as turning vertical scroll bars on and
off should shrink your frame by about two columns.

martin