bug#32848: 26.1; follow-mode cursor move breaks with frame-resize-pixelwise

[Eli Zaretskii]

> Date: Fri, 28 Sep 2018 20:31:51 +0000
> Cc: Allen Li <darkfeline@felesatra.moe>, Anders Lindgren <andlind@gmail.com>,
>   32848@debbugs.gnu.org
> From: Alan Mackenzie <acm@muc.de>
> 
> (iv) Redisplay sees w->force_start true and
> make_cursor_line_fully_visible_p also true.  These conflict with
> eachother here.  Priority is given to make_cursor_...._p.
> 
> Why does w->force_start not have priority here?

Because by default we don't want to show the cursor in a partial line,
ever: such a line might not be legible.  Over the years, more and more
rare use cases were reported where such a situation happens, and we
fixed them one by one.  Evidently, this is the popular demand.

Follow-mode is special in this regard, because with it, showing a
partial line is not a flaw, as that same line will be fully visible in
the next window, and follow-mode actually switches to that next
window.  So we need to tell the display engine to behave specially in
this case.  I suggested 2 ways of doing that, the simple one actually
does what you expected, i.e. the force_start flag will win.