Fix redisplay after a large insertion

* src/xdisp.c (redisplay_internal): Don't accept the results of
"optimization 3" if the cursor ends up in a partially visible
glyph row.  (Bug22637)

1 files changed, 9 insertions, 3 deletions

diff --git a/src/xdisp.c b/src/xdisp.c
index 8f1e98d99ef..840699d00fb 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -825,6 +825,7 @@ static Lisp_Object redisplay_window_1 (Lisp_Object);
 static bool set_cursor_from_row (struct window *, struct glyph_row *,
                                  struct glyph_matrix *, ptrdiff_t, ptrdiff_t,
                                  int, int);
+static bool cursor_row_fully_visible_p (struct window *, bool, bool);
 static bool update_menu_bar (struct frame *, bool, bool);
 static bool try_window_reusing_current_matrix (struct window *);
 static int try_window_id (struct window *);
@@ -13881,11 +13882,16 @@ redisplay_internal (void)
               eassert (this_line_vpos == it.vpos);
               eassert (this_line_y == it.current_y);
               set_cursor_from_row (w, row, w->current_matrix, 0, 0, 0, 0);
+              if (cursor_row_fully_visible_p (w, false, true))
+                {
 #ifdef GLYPH_DEBUG
-              *w->desired_matrix->method = 0;
-              debug_method_add (w, "optimization 3");
+                  *w->desired_matrix->method = 0;
+                  debug_method_add (w, "optimization 3");
 #endif
-              goto update;
+                  goto update;
+                }
+              else
+                goto cancel;
             }
           else
             goto cancel;