Bug 380153 - SetupClusterBoundaries uses unset attrs from pango_break after NUL.

p=Karl Tomlinson <mozbugz@karlt.net>
r=roc

gfx/thebes/src/gfxPangoFonts.cpp

@@ -1049,13 +1049,14 @@ SetupClusterBoundaries(gfxTextRun* aTextRun, const gchar *aUTF8, PRUint32 aUTF8L
     if (!buffer.AppendElements(aUTF8Length + 1))
         return;
 
-    pango_break(aUTF8, aUTF8Length, aAnalysis,
-                buffer.Elements(), buffer.Length());
-
     const gchar *p = aUTF8;
     const gchar *end = aUTF8 + aUTF8Length;
-    const PangoLogAttr *attr = buffer.Elements();
     gfxTextRun::CompressedGlyph g;
+
+    while (p < end) {
+        PangoLogAttr *attr = buffer.Elements();
+        pango_break(p, end - p, aAnalysis, attr, buffer.Length());
+
         while (p < end) {
             if (!attr->is_cursor_position) {
                 aTextRun->SetCharacterGlyph(aUTF16Offset, g.SetClusterContinuation());
@@ -1070,6 +1071,14 @@ SetupClusterBoundaries(gfxTextRun* aTextRun, const gchar *aUTF8, PRUint32 aUTF8L
             // We produced this utf8 so we don't need to worry about malformed stuff
             p = g_utf8_next_char(p);
             ++attr;
+
+            if (ch == 0) {
+                // pango_break (pango 1.16.2) only analyses text before the
+                // first NUL (but sets one extra attr), so call pango_break
+                // again to analyse after the NUL.
+                break;
+            }
+        }
     }
 }