Fix assertion violation when restoring hscrolled window configurations.

 src/xdisp.c (hscroll_window_tree): Don't try hscrolling windows whose cursor
 row has zero buffer position as their start position.  Reported by
 Martin Rudalics <rudalics@gmx.at>.

2 files changed, 10 insertions, 0 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 463c895e5da..737a5078b24 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -4,6 +4,9 @@
         buffer position where we are to start the iteration.
         (handle_invisible_prop): Record in it->stop_charpos the position
         where the invisible text ends.  (Bug#18035)
+        (hscroll_window_tree): Don't try hscrolling windows whose cursor
+        row has zero buffer position as their start position.  Reported by
+        martin rudalics <rudalics@gmx.at>.
 
 2014-07-16  Eli Zaretskii  <eliz@gnu.org>
 
diff --git a/src/xdisp.c b/src/xdisp.c
index 3ab1dd76654..d1016b6b8d7 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -12880,6 +12880,13 @@ hscroll_window_tree (Lisp_Object window)
           h_margin = hscroll_margin * WINDOW_FRAME_COLUMN_WIDTH (w);
 
           if (!NILP (Fbuffer_local_value (Qauto_hscroll_mode, w->contents))
+              /* In some pathological cases, like restoring a window
+                 configuration into a frame that is much smaller than
+                 the one from which the configuration was saved, we
+                 get glyph rows whose start and end have zero buffer
+                 positions, which we cannot handle below.  Just skip
+                 such windows.  */
+              && CHARPOS (cursor_row->start.pos) >= BUF_BEG (w->contents)
               /* For left-to-right rows, hscroll when cursor is either
                  (i) inside the right hscroll margin, or (ii) if it is
                  inside the left margin and the window is already