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styling: update based on list feedback

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Sam Whited 2017-11-08 17:20:30 -06:00
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inbox/styling.xml
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@ -10,8 +10,8 @@
<header>
<title>Message Styling</title>
<abstract>
This specification defines a plain-text formatting syntax for use in
exchanging instant messages with simple text styling.
This specification defines a formatted text syntax for use in instant
messages with simple text styling.
</abstract>
&LEGALNOTICE;
<number>xxxx</number>
@ -39,15 +39,14 @@
Historically, XMPP has had no system for simple text styling.
Instead, specifications like &xep0071; that require full layout engines have
been used, leading to numerous security issues with implementations.
Some clients have also performed their own formatting based on identifiers
in the body.
While this has worked well for those clients, it is not interoperable and
leads to clients each supporting their own informal styling languages.
Some entities have also performed their own styling based on identifiers in
the body.
While this has worked well in the past, it is not interoperable and leads to
entities each supporting their own informal styling languages.
</p>
<p>
This specification aims to provide a single, interoperable text styling
language that can be used by entities that do not require full layout
engines.
This specification aims to provide a single, interoperable formatted text
syntax that can be used by entities that do not require full layout engines.
</p>
</section1>
<section1 topic='Requirements' anchor='reqs'>
@ -89,6 +88,7 @@
Many important terms used in this document are defined in &unicode;.
The terms "left-to-right" (LTR) and "right-to-left" (RTL) are defined in
&uax9;.
The term "formatted text" is defined in &rfc7764;.
</p>
<dl>
<di>
@ -99,14 +99,6 @@
text style.
</dd>
</di>
<di>
<dt>Formatted text</dt>
<dd>
Text that includes non-textual information coded in a particular way
that affects the interpretation of the text by computer programs
(&rfc7764;).
</dd>
</di>
<di>
<dt>Plain text</dt>
<dd>
@ -126,7 +118,7 @@
<section1 topic='Use Cases' anchor='usecases'>
<ul>
<li>
As an user sending an instant message to a friend, I want to be able to
As a user sending an instant message to a friend, I want to be able to
emphasize an important part of my message.
</li>
<li>
@ -139,62 +131,40 @@
</li>
</ul>
</section1>
<section1 topic='Discovering support' anchor='disco'>
<section2 topic='Explicit Discovery' anchor='discovery-explicit'>
<p>
If an entity supports this specification it MUST advertise the fact by
returning a feature of 'urn:xmpp:styling:0' &VNOTE; in response to a
&xep0030; information request (or by advertising this namespace in the
dynamic profile of service discovery defined in &xep0115;).
</p>
<example caption='Disco response'><![CDATA[
<iq type='result'
from='viola@example.net/seashore-Iaqu8ith'
to='captain@example.net/illyria-rohJa9au'
id='Uw8riPhe'>
<query xmlns='http://jabber.org/protocol/disco#info'>
<feature var='urn:xmpp:styling:0' />
</query>
</iq>
]]></example>
</section2>
<section2 topic='Implicit Discovery' anchor='discovery-implicit'>
<p>
An entity supporting this specification SHOULD render all messages
&lt;body&gt; elements using this specification and MAY choose to send
messages formatted using this specification even if the other end has not
advertised support.
</p>
</section2>
</section1>
<section1 topic='Business Rules' anchor='rules'>
<section2 topic='Display' anchor='display'>
<section2 topic='Blocks' anchor='block'>
<p>
Formatting characters MAY be displayed styled along with the span they
apply to or they may be hidden and the styling only applied to the span.
For instance, given the string "*emphasis*" both of the following are
valid renderings:
A block is any chunk of text that can be parsed unambiguously in one pass.
</p>
<ul>
<li><strong>*emphasis*</strong></li>
<li><strong>emphasis</strong></li>
<li>A single line of text containing only inline spans</li>
<li>A block quotation comprising one or more lines</li>
<li>A preformatted code block</li>
</ul>
</section2>
<section2 topic='Spans' anchor='span'>
<p>
A span are groups of text that do not result in a line break when rendered
(they are rendered inline) and where the entire group is rendered in the
same manner and in the same block.
Spans may be either plain text with no formatting applied, or may be
formatted text that is enclosed by two styling directives.
The following are all single spans:
</p>
<ul>
<li>plain span</li>
<li><strong>*emphasized span*</strong></li>
</ul>
<p>
Examples in this document will display the formatting characters for
clarity.
Matches of spans between two styling directives MUST contain some text
between the two styling directives and the opening styling directive MUST
be located at the beginning of the line, or after a whitespace character.
The opening styling directive MUST also not be followed by a whitespace
character.
Spans are always parsed from the beginning of the byte stream to the end
and are lazily matched.
</p>
</section2>
<section2 topic='Inlines' anchor='emph'>
<p>
Inline styling directives are evaluated lazily from the start of the byte
stream (the left in left-to-right languages and the right in right-to-left
languages).
Matches MUST NOT extend over newlines and MUST start with a whitespace
character or be the beginning of the line or the byte stream.
Matches MUST contain some text between the two styling directives.
Inline styling directives may also be doubled to allow the single
character version of the directive to be styled.
That is to say, "**emphasis**" is rendered the same as "*emphasis*".
For example, the word "emphasized" would be styled in each of the
following messages:
</p>
@ -203,53 +173,46 @@
<li>foo <strong>*emphasized*</strong> bar</li>
<li><strong>*emphasized*</strong>foo<strong>*emphasized*</strong></li>
<li><strong>*emphasized*</strong>foo*</li>
<li><strong>**emphasi*zed**</strong> foo*</li>
<li>* <strong>*emphasized*</strong></li>
<li>* foo <strong>*emphasized*</strong></li>
</ul>
<p>
Nothing would be formatted in the following messages (where / represents a
Nothing would be styled in the following messages (where \n represents a
new line):
</p>
<ul>
<li>not emphasized*</li>
<li>*not emphasized</li>
<li>*not / emphasized*</li>
<li>*not \n emphasized*</li>
<li>**</li>
<li>****</li>
</ul>
</section2>
<section2 topic='Order of Operations' anchor='oporder'>
<p>
Block level styling such as preformatted blocks and quotations is always
handled before inlines such as emphasis and inline preformatted text.
</p>
</section2>
<section2 topic='Bold' anchor='bold'>
<p>
Text enclosed by '*' (U+002A ASTERISK) MUST be displayed with a greater
Text enclosed by '*' (U+002A ASTERISK) SHOULD be displayed with a greater
weight than the surrounding text (bold face).
</p>
<example caption='Bold'><![CDATA[
<body>
The full title is **Twelfth Night, or What You Will** but
The full title is *Twelfth Night, or What You Will* but
*most* people shorten it.
</body>
]]></example>
</section2>
<section2 topic='Italic' anchor='italic'>
<p>
Text enclosed by '_'(U+005F LOW LINE) MUST be displayed in italics.
Text enclosed by '_' (U+005F LOW LINE) SHOULD be displayed in italics.
</p>
<example caption='Italic'><![CDATA[
<body>
The full title is _Twelfth Night, or What You Will_ but
__most__ people shorten it.
_most_ people shorten it.
</body>
]]></example>
</section2>
<section2 topic='Strike through' anchor='strike'>
<p>
Text enclosed by '~'(U+007E TILDE) MUST be displayed with a horizontal
Text enclosed by '~' (U+007E TILDE) SHOULD be displayed with a horizontal
line through the middle (strike through).
</p>
<example caption='Strike through'><![CDATA[
@ -258,10 +221,10 @@
</body>
]]></example>
</section2>
<section2 topic='Preformatted Inline Text' anchor='pre-inline'>
<section2 topic='Inline Preformatted Text' anchor='pre-inline'>
<p>
Text enclosed by a '`' (U+0060 GRAVE ACCENT) MUST be displayed inline in a
monospace font.
Text enclosed by a '`' (U+0060 GRAVE ACCENT) SHOULD be displayed inline in
a monospace font.
Inline formatting directives inside the inline preformatted text are not
rendered.
For example, in the following the word "monospace" is valid pre-formatted
@ -274,17 +237,20 @@
</ul>
<example caption='Monospace text'><![CDATA[
<body>
Wow, I can write in `monospace`, even a literal ``backtick (`)``!
Wow, I can write in `monospace`!
</body>
]]></example>
</section2>
<section2 topic='Preformatted Block Text' anchor='pre-block'>
<p>
A block of text surrounded by lines consisting of a sequence of three
backticks (U+0060 GRAVE ACCENT), "```", is preformatted text and should be
backticks, "```" (U+0060 GRAVE ACCENT), is preformatted text and should be
displayed exactly as it was entered including whitespace.
No other formatting described in this document should be rendered inside
a preformatted text block.
If no closing "```" sequence exists, the preformatted block extends to the
end of the input stream or the end of the parent block (whichever comes
first).
No other formatting described in this document should be rendered inside a
preformatted text block.
</p>
<example caption='Preformatted block text'><![CDATA[
<body>
@ -292,16 +258,26 @@
(println &quot;Hello, world!&quot;)
```
This should show up as monospaced, preformatted text ⤴
This should show up as monospace, preformatted text ⤴
</body>
]]></example>
<example caption='No closing preformatted text sequence'><![CDATA[
<body>
&gt; ```
&gt; (println &quot;Hello, world!&quot;)
The entire blockquote is a preformatted text block, but this line is
plaintext!
</body>
]]></example>
</section2>
<section2 topic='Quotations' anchor='quote'>
<p>
A quotation is indicated by one or more lines with a byte stream beginning
with a '&gt;' (U+003E GREATER-THAN SIGN) immediately followed by a
whitespace character.
Inline formatting is rendered inside of quotations.
with a '&gt;' (U+003E GREATER-THAN SIGN).
Block quotes may contain any child block, including other quotations.
Lines inside the block quote MUST have leading spaces trimmed before
parsing the child block.
</p>
<example caption='Quotation (LTR)'><![CDATA[
<body>
@ -322,9 +298,19 @@
</section1>
<section1 topic='Implementation Notes' anchor='impl'>
<p>
The rules for inline styling form a context free grammar that cannot be
This document does not define a regular grammar and thus styling cannot be
matched by a regular expression.
A simple stack based parser is recommended instead.
Instead, a predictive recursive descent or LALR parser may be constructed.
For instance, a simple parser can be constructed by first parsing all text
into blocks and then recursively parsing the child-blocks inside block
quotations, the spans inside plain lines, and by returning the text inside
preformatted blocks without modification.
</p>
<p>
It is RECOMMENDED that formatting characters be displayed and formatted in
the same manner as the text they apply to.
For example, the string "*emphasis*" would be rendered as
"<strong>*emphasis*</strong>".
</p>
</section1>
<section1 topic='Accessibility Considerations' anchor='access'>
@ -333,6 +319,11 @@
sufficient contrast exists between styled and unstyled text so that users
with vision deficiencies are able to distinguish between the two.
</p>
<p>
Formatted text may also be rendered poorly by screen readers.
When applying formatting it may be desirable to include directives to
exclude formatting characters from being read.
</p>
</section1>
<section1 topic='Internationalization Considerations' anchor='i18n'>
<p>OPTIONAL.</p>
@ -346,20 +337,7 @@
</p>
</section1>
<section1 topic='XMPP Registrar Considerations' anchor='registrar'>
<p>This specification defines the following XML namespaces:</p>
<ul>
<li>urn:xmpp:styling:0</li>
</ul>
<p>
The &REGISTRAR; shall include the foregoing namespaces in its disco
features registry as defined in &xep0030;.
</p>
<code caption='Registry Submission'><![CDATA[
<var>
<name>urn:xmpp:styling:0</name>
<desc>Indicates support for simple message styling.</desc>
<doc>XEP-XXXX</doc>
</var>]]></code>
<p>This specification requires no interaction with the &REGISTRAR;</p>
</section1>
<section1 topic='XML Schema' anchor='schema'>
<p>This document does not define any new XML structure requiring a schema.</p>