[gspell] inline-checker-text-buffer: add assertions around check_subregion()

[Sébastien Wilmet <swilmet src gnome org>]

commit a4e70b6ed08becdd851fbfd88b523f3bc813f313
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Thu Mar 3 17:22:18 2016 +0100

    inline-checker-text-buffer: add assertions around check_subregion()

 gspell/gspell-inline-checker-text-buffer.c |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)
---
diff --git a/gspell/gspell-inline-checker-text-buffer.c b/gspell/gspell-inline-checker-text-buffer.c
index fe3f9d0..a7d5468 100644
--- a/gspell/gspell-inline-checker-text-buffer.c
+++ b/gspell/gspell-inline-checker-text-buffer.c
@@ -375,6 +375,8 @@ check_visible_region_in_view (GspellInlineCheckerTextBuffer *spell,
        {
                GtkTextIter start;
                GtkTextIter end;
+               GtkTextIter orig_start;
+               GtkTextIter orig_end;
 
                if (!_gspell_text_region_iterator_get_subregion (&intersect_iter,
                                                                 &start,
@@ -383,8 +385,18 @@ check_visible_region_in_view (GspellInlineCheckerTextBuffer *spell,
                        break;
                }
 
+               orig_start = start;
+               orig_end = end;
+
                check_subregion (spell, &start, &end);
 
+               /* Ensure that we don't have an infinite loop. We must subtract
+                * from scan_region at least [start, end], otherwise we will
+                * re-check the same subregion again and again.
+                */
+               g_assert (gtk_text_iter_compare (&start, &orig_start) <= 0);
+               g_assert (gtk_text_iter_compare (&orig_end, &end) <= 0);
+
                _gspell_text_region_subtract (spell->scan_region, &start, &end);
 
                _gspell_text_region_iterator_next (&intersect_iter);