- * regular zero-terminated C strings (possibly empty), never NULL pointers,
- * so they can be safely used in printf() and other string-handling functions.
+ * the "text" field as a regular zero-terminated C string (possibly
+ * empty), never a NULL pointer, so it can be safely used in printf() and
+ * other string-handling functions. Note that the "itxt_length", "lang", and
+ * "lang_key" members of the structure only exist when the library is built
+ * with iTXt chunk support. Prior to libpng-1.4.0 the library was built by
+ * default without iTXt support. Also note that when iTXt *is* supported,
+ * the "lang" and "lang_key" fields contain NULL pointers when the
+ * "compression" field contains * PNG_TEXT_COMPRESSION_NONE or
+ * PNG_TEXT_COMPRESSION_zTXt. Note that the "compression value" is not the
+ * same as what appears in the PNG tEXt/zTXt/iTXt chunk's "compression flag"
+ * which is always 0 or 1, or its "compression method" which is always 0.