XMPP-based Instant Messages has suffered from a lack of proper message styling mechanisms. After abandoning XHTML-IM (XEP-0071) [1] for its horrible security track record, Message Styling (XEP-0393) [2] and Message Markup (XEP-0394) [3] were proposed as replacements, but neither was able to gain sufficient traction to become the default styling mechanism.
This specification fills the gap by formally specifying the Unicode-based formatting that is currently fancied on Social Media and micro-blogging as an XMPP standard for Instant Messaging. As XMPP is based on UTF-8, messages formatted with this mechanism are immediately visible on all receiving clients. Simple third-party tools can be used for writing messages until this specification is integrated into the IM message input boxes.
This specification relies on Unicode features introduced in the 3.1 specification. As XMPP implementations are required to support Unicode 3.2 for StringPrep during SASL authentication, no new requirements arise.
To format a string as Preformatted Text, the individual code-points need
to be converted to their integer representation, then increased by
0x1D62F (capital letters) or 0x1D629 (lowercase letters)
and then converted back to characters.
To format a string with Emphasis, the individual code-points need
to be converted to their integer representation, then increased by
0x1D3F3 (capital letters) or 0x1D3ED (lowercase letters)
and then converted back to characters.
To format a string with Strong Emphasis, the individual code-points need
to be converted to their integer representation, then increased by
0x1D3BF (capital letters) or 0x1D3B9 (lowercase letters)
and then converted back to characters.
To format a string with Very Very Strong Emphasis, the individual code-points need
to be converted to their integer representation, then increased by
0x1D427 (capital letters) or 0x1D421 (lowercase letters)
and then converted back to characters.
To format a string as struck through, each code-point needs to be extended with a U-0336 COMBINING LONG STROKE OVERLAY postfix.
Some clients will use a serif-less font instead of a serif font to display
instant messages, or even allow the user to choose an arbitrary font. The
formatting defined in this document assumes the use of serif fonts, however.
If a formatted text is to be displayed in a context that is not supposed to
render serifs, the displaying implementation MUST add 0x1D4 to the
respective integer representations of the fancy code-points.
On the wire, the serif representation always MUST be used.
Determining whether a given display font is serif or sans-serif is out of scope of this specification.
𝞜𝞸𝞰𝞮
🇳🇴🇳🇪
The rendering of fonts is a complex task performed in the most inner guts of the operating system. Over the last decades, various exploits have been discovered in all major operating systems. Unfortunately, fixing those issues is far beyond the abilities of a simple XMPP client.
This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [4].
None.
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The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 6120) and XMPP IM (RFC 6121) specifications contributed by the XMPP Standards Foundation to the Internet Standards Process, which is managed by the Internet Engineering Task Force in accordance with RFC 2026. Any protocol defined in this document has been developed outside the Internet Standards Process and is to be understood as an extension to XMPP rather than as an evolution, development, or modification of XMPP itself.
The primary venue for discussion of XMPP Extension Protocols is the <standards@xmpp.org> discussion list.
Discussion on other xmpp.org discussion lists might also be appropriate; see <http://xmpp.org/about/discuss.shtml> for a complete list.
Errata can be sent to <editor@xmpp.org>.
The following requirements keywords as used in this document are to be interpreted as described in RFC 2119: "MUST", "SHALL", "REQUIRED"; "MUST NOT", "SHALL NOT"; "SHOULD", "RECOMMENDED"; "SHOULD NOT", "NOT RECOMMENDED"; "MAY", "OPTIONAL".
1. XEP-0071: XHTML-IM <https://xmpp.org/extensions/xep-0071.html>.
2. XEP-0393: Message Styling <https://xmpp.org/extensions/xep-0393.html>.
3. XEP-0394: Message Markup <https://xmpp.org/extensions/xep-0394.html>.
4. The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>.
Note: Older versions of this specification might be available at http://xmpp.org/extensions/attic/
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