[arabic] Add note re disabled 'cswh'
diff --git a/src/hb-ot-shape-complex-arabic.cc b/src/hb-ot-shape-complex-arabic.cc
index 1b4ebc9..b90abfe 100644
--- a/src/hb-ot-shape-complex-arabic.cc
+++ b/src/hb-ot-shape-complex-arabic.cc
@@ -184,6 +184,15 @@
map->add_global_bool_feature (HB_TAG('c','a','l','t'));
map->add_gsub_pause (NULL);
+ /* The spec includes 'cswh'. Earlier versions of Windows
+ * used to enable this by default, but testing suggests
+ * that Windows 8 and later do not enable it by default,
+ * and spec now says 'Off by default'.
+ * We disabled this in ae23c24c32.
+ * Note that IranNastaliq uses this feature extensively
+ * to fixup broken glyph sequences. Oh well...
+ * Test case: U+0643,U+0640,U+0631. */
+ map->add_global_bool_feature (HB_TAG('c','s','w','h'));
map->add_global_bool_feature (HB_TAG('m','s','e','t'));
}
