[pango] [break-thai] Fix two bugs in libthai glue layer

[Behdad Esfahbod <behdad src gnome org>]

commit c6d6cfff40ba2e80c2fda7d33d2942a0b4a2d14a
Author: Behdad Esfahbod <behdad behdad org>
Date:   Tue May 23 22:14:36 2017 -0700

    [break-thai] Fix two bugs in libthai glue layer
    
    First bug is, we were passing as count to th_brk, the UTF-8
    length instead of TIS length.  Ouch!  I'm not sure how this
    was never caught...
    
    The other one was, break-thai was possibly marking a position
    is_line_break when break.c has already set it to is_char_break=FALSE.
    This broke the invariant that if a position is line-break, then it
    must be char-break as well.  This, in turn was hitting assertions
    in certain conditions.  Hit it with this for example:
    
    $ ./pango-view --text 'ส์" (S' --width 43 --font 156px
    
    Note that in a correct world the Latin part of that string should
    not reach break-thai.c at all, but that's not how pango-layout.c
    breaks right now.  See comment before pango_break() call in
    pango-layout.c.

 pango/break-thai.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)
---
diff --git a/pango/break-thai.c b/pango/break-thai.c
index 5560c9f..c9bf3e8 100644
--- a/pango/break-thai.c
+++ b/pango/break-thai.c
@@ -83,10 +83,15 @@ break_thai (const char          *text,
   /* find line break positions */
 
   G_LOCK (th_brk);
-  len = th_brk (tis_text, brk_pnts, len);
+  len = th_brk (tis_text, brk_pnts, cnt);
   G_UNLOCK (th_brk);
   for (cnt = 0; cnt < len; cnt++)
+    if (attrs[brk_pnts[cnt]].is_char_break)
     {
+      /* Only allow additional line breaks if line-breaking is NOT
+       * prohibited. (The alternative would be to set is_char_break to
+       * TRUE as well.  NOT setting it will break invariants that any
+       * line break opportunity is also a char break opportunity. */
       attrs[brk_pnts[cnt]].is_line_break = TRUE;
       attrs[brk_pnts[cnt]].is_word_start = TRUE;
       attrs[brk_pnts[cnt]].is_word_end = TRUE;