bug#36832: Supply option to suppress scrolling in compilation mode buffers.

[Alan Mackenzie <acm@muc.de>]

Hello, Eli.

On Wed, Jul 31, 2019 at 17:21:49 +0300, Eli Zaretskii wrote:
> > Date: Tue, 30 Jul 2019 19:32:35 +0000
> > Cc: 36832@debbugs.gnu.org
> > From: Alan Mackenzie <acm@muc.de>

> > The current code does two things, sometimes, on <CR> being hit: (i) it
> > puts an indicator into the fringe; (ii) it scrolls the compile mode
> > window upwards, the pertinent line moving either to the top, or to a
> > specified window line.

> > Unfortunately, the code which does these things seems to be fragmented,
> > and there is just one user option to control (i) and (ii) above.

> > One solution would be always to mark to the line in the compile mode
> > window, whether by an indicator in the fringe or a ">" or "=>" at column
> > 0.  Then only scroll the compile mode window when the user has explicitly
> > requested this by the user option compilation-context-lines.

> Yes, that would be an okay solution.

I've just committed a patch to master which does the above.  When
compilation-context-lines has the value t, it no longer scrolls the
compilation-mode buffer line to the top of the window, instead using an
overlay with before-string property "=>" to mark the current line.

This time, the changes are entirely within compile.el.  (Plus a
documentation change and a NEWS entry.)

If there are no objections, I'll close this bug as fixed.

-- 
Alan Mackenzie (Nuremberg, Germany).