Avoid infloop when scrolling conservatively (Bug#7537).

* src/xdisp.c (try_scrolling): Avoid infloop if the first line is obscured
due to a vscroll (Bug#7537).

2 files changed, 10 insertions, 1 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 025161cc395..95f7039eaf7 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2010-12-05  Chong Yidong  <cyd@stupidchicken.com>
+
+        * xdisp.c (try_scrolling): Avoid infloop if the first line is
+        obscured due to a vscroll (Bug#7537).
+
 2010-12-02  Jan Djärv  <jhd@zeplinf.localdomain>
 
         * nsterm.h (FRAME_NS_TOOLBAR_HEIGHT): Rename to FRAME_TOOLBAR_HEIGHT.
diff --git a/src/xdisp.c b/src/xdisp.c
index a416c8ff435..dbe3e443c67 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -12759,7 +12759,11 @@ try_scrolling (window, just_this_one_p, scroll_conservatively,
 
       /* If cursor ends up on a partially visible line,
          treat that as being off the bottom of the screen.  */
-      if (! cursor_row_fully_visible_p (w, extra_scroll_margin_lines <= 1, 0))
+      if (! cursor_row_fully_visible_p (w, extra_scroll_margin_lines <= 1, 0)
+          /* It's possible that the cursor is on the first line of the
+             buffer, which is partially obscured due to a vscroll
+             (Bug#7537).  In that case, avoid looping forever . */
+          && extra_scroll_margin_lines < w->desired_matrix->nrows - 1)
         {
           clear_glyph_matrix (w->desired_matrix);
           ++extra_scroll_margin_lines;