[ot-color] Make PNGHeader reading actually work

src/hb-ot-color-sbix-table.hh

@@ -198,7 +198,7 @@ struct sbix
 
     struct PNGHeader
     {
-      HBUINT8 header[9];
+      HBUINT8 header[16];
       HBUINT32 width;
       HBUINT32 height;
     };
@@ -209,7 +209,7 @@ struct sbix
 				 hb_glyph_extents_t *extents) const
     {
       if (likely (sbix_len == 0))
-        return hb_blob_get_empty ();
+        return false;
 
       int x_offset, y_offset;
       hb_blob_t *blob = reference_blob_for_glyph (glyph, x_ppem, y_ppem,
@@ -221,7 +221,7 @@ struct sbix
       extents->x_bearing = x_offset;
       extents->y_bearing = y_offset;
       const PNGHeader &header = *blob->as<PNGHeader>();
-      extents->width     = header.width + 100;
+      extents->width     = header.width;
       extents->height    = header.height;
       hb_blob_destroy (blob);
 

test/api/test-ot-color.c

@@ -427,8 +427,8 @@ test_hb_ot_color_png (void)
   hb_font_get_glyph_extents (sbix_font, 1, &extents);
   g_assert_cmpint (extents.x_bearing, ==, 0);
   g_assert_cmpint (extents.y_bearing, ==, 0);
-  g_assert_cmpint (extents.width, ==, 3501);
-  g_assert_cmpint (extents.height, ==, 20992);
+  g_assert_cmpint (extents.width, ==, 300);
+  g_assert_cmpint (extents.height, ==, 300);
   hb_blob_destroy (blob);
   hb_font_destroy (sbix_font);