Prevent hinting if there are too many segments.
This speeds up handling of broken glyphs.
Reported as
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=35309
* src/autofit/aflatin.c (af_latin_hints_compute_segments): Implement
it.
diff --git a/ChangeLog b/ChangeLog
index 7bd450a..522d084 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,16 @@
+2021-06-19 Werner Lemberg <david@freetype.org>
+
+ [autofit] Prevent hinting if there are too many segments.
+
+ This speeds up handling of broken glyphs.
+
+ Reported as
+
+ https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=35309
+
+ * src/autofit/aflatin.c (af_latin_hints_compute_segments): Implement
+ it.
+
2021-06-18 Alexei Podtelezhnikov <apodtele@gmail.com>
* src/sdf/ftsdfrend.c (ft_(b)sdf_render): Do not FT_ERROR routinely.
diff --git a/src/autofit/aflatin.c b/src/autofit/aflatin.c
index ef90c93..8ca6ac2 100644
--- a/src/autofit/aflatin.c
+++ b/src/autofit/aflatin.c
@@ -1847,6 +1847,31 @@
( FT_ABS( point->out_dir ) == major_dir ||
point == point->prev ) )
{
+ /*
+ * For efficiency, we restrict the number of segments to 1000,
+ * which is a heuristic value: it is very unlikely that a glyph
+ * with so many segments can be hinted in a sensible way.
+ * Reasons:
+ *
+ * - The glyph has really 1000 segments; this implies that it has
+ * at least 2000 outline points. Assuming 'normal' fonts that
+ * have superfluous points optimized away, viewing such a glyph
+ * only makes sense at large magnifications where hinting
+ * isn't applied anyway.
+ *
+ * - We have a broken glyph. Hinting doesn't make sense in this
+ * case either.
+ */
+ if ( axis->num_segments > 1000 )
+ {
+ FT_TRACE0(( "af_latin_hints_compute_segments:"
+ " more than 1000 segments in this glyph;\n" ));
+ FT_TRACE0(( " "
+ " hinting is suppressed\n" ));
+ axis->num_segments = 0;
+ return FT_Err_Ok;
+ }
+
/* this is the start of a new segment! */
segment_dir = (AF_Direction)point->out_dir;
