hb-font: Document length limit for glyph names
This is useful information for users of the
hb_font_get_glyph_name() API.
diff --git a/src/hb-font.cc b/src/hb-font.cc
index f2127c2..da5162b 100644
--- a/src/hb-font.cc
+++ b/src/hb-font.cc
@@ -1343,6 +1343,9 @@
*
* Fetches the glyph-name string for a glyph ID in the specified @font.
*
+ * According to the OpenType specification, glyph names are limited to 63
+ * characters and can only contain (a subset of) ASCII.
+ *
* Return value: `true` if data found, `false` otherwise
*
* Since: 0.9.2
