bug#27008: 26.0.50; auto-hscroll-mode and scroll-left

[Eli Zaretskii]

> Date: Tue, 30 May 2017 20:18:27 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 27008@debbugs.gnu.org
> 
> > From: Stephen Berman <stephen.berman@gmx.net>
> > Cc: 27008@debbugs.gnu.org
> > Date: Tue, 30 May 2017 18:57:01 +0200
> > 
> > Thanks very much for pursuing this.  I updated my master branch, applied
> > your patch and rebuilt, but when I executed the recipe of my OP, I saw
> > the same effect with the patch as without it: only the current line
> > respects w->min_hscroll, the other are displayed from BOL.  I'd be happy
> > to try and help diagnose this further, if you can advise me what to do.
> 
> I don't have any advice, because your recipe worked for me after the
> changes.  I'm confused now.

Ah, I see: I sent the wrong patch.  Here's the right one:

diff --git a/src/xdisp.c b/src/xdisp.c
index ddb26b8..3ccd035 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -2890,8 +2890,19 @@ init_iterator (struct it *it, struct window *w,
     }
   else
     {
+      /* When hscrolling only the current line, don't apply the
+        hscroll here, it will be applied by display_line when it gets
+        to laying out the line showing point.  However, if the
+        window's min_hscroll is positive, the user specified a lower
+        bound for automatic hscrolling, so they expect the
+        non-current lines to obey that hscroll amount.  */
       if (hscrolling_current_line_p (w))
-       it->first_visible_x = 0;
+       {
+         if (w->min_hscroll > 0)
+           it->first_visible_x = w->min_hscroll * FRAME_COLUMN_WIDTH (it->f);
+         else
+           it->first_visible_x = 0;
+       }
       else
        it->first_visible_x =
          window_hscroll_limited (w, it->f) * FRAME_COLUMN_WIDTH (it->f);