Re: WebVTT bidi: can we have ‎ and ‏ escapes?

These marks, no, they are not terminated by anything. They are freestanding.

LRE, LRO, RLE, and RLO are terminated (by PDF), since they do start a
"span", but the marks don't.

    /Kent K


Den 2011-12-08 17:48, skrev "Phillips, Addison" <addison@lab126.com>:

> You need a third character: U+202C (PDF). Sequences starting with RLM or LRM
> are terminated using this character. See:
> http://www.w3.org/International/questions/qa-bidi-controls.en.php
>  
> Addison
>  
> Addison Phillips
> Globalization Architect (Lab126)
> Chair (W3C I18N WG)
>  
> Internationalization is not a feature.
> It is an architecture.
>  
>  
>  
> 
> From: Aharon (Vladimir) Lanin [mailto:aharon@google.com]
> Sent: Thursday, December 08, 2011 12:43 AM
> To: public-texttracks@w3.org; public-i18n-bidi@w3.org
> Subject: WebVTT bidi: can we have &lrm; and &rlm; escapes?
>  
> 
> The WebVTT spec currently allows just three escapes: &lt;, &gt;, and &amp;.
> Authors are expected to enter any other characters directly by whatever other
> means they have at their disposal.
> 
>  
> 
> I would like to suggest that an exception is needed for two more characters,
> LRM and RLM. These are invisible characters with strong directionality, LTR
> for one and RTL for the other. These are used in bidi text in two ways:
> 
>  
> 
> - At the start of a paragrph, one of these can be used to indicate the
> paragraph's overall directionality in contexts where the directionality is
> determined by the paragraph's first character with strong direction. This is
> the default method of determining paragraph direction specified by the Unicode
> Bidirectional Algorithm - and the *only* method allowed by the current WebVTT
> spec. It is important to note that RTL languages fairly often use "words"
> spelled in LTR characters, e.g. acronyms like GPS and HTML (and WebVTT), as
> well as brand names. Occasionally, these occur as the first word in a sentence
> or even a paragraph, and when this is the case, the overall directionality of
> the paragraph is set incorrectly, unless one puts an RLM at the beginning of
> the paragraph.
> 
>  
> 
> - In bidi text, these characters provide some means of control over the visual
> ordering of the characters. For example, to get "Mamma Mia!" to come out that
> way - and not as "!Mamma Mia" - in RTL text, one can put an LRM after the
> exclamation mark. In HTML, there are other means of such control, such as
> wrapping opposite-direction phrases in <span dir=...> or in a <bdi> element.
> But such means are absent in WebVTT.
> 
>  
> 
> There are several reasons that I think an exception should be made for these
> characters and escapes provided for them in WebVTT:
> 
>  
> 
> 1. As mentioned above, WebVTT does not provide any means for controlling
> paragraph directionality or inline directionality explicitly. Thus, the author
> has no means but LRM and RLM for such control in a WebVTT file.
> 
>  
> 
> 2. LRM and RLM are invisible. Entering invisible characters and editing text
> that already contains them is confusing.
> 
>  
> 
> 3. The existing standard Hebrew and Arabic keyboards do not provide a means of
> generating an actual LRM or RLM. Although the Windows native TextBox control
> provides a context menu that allows inserting various special characters
> including LRM and RLM, and Microsoft Notepad uses TextBox and thus provides
> the same context menu, most reasonable text editors available on Windows (e.g.
> Notepad++) are not based on TextBox and do not provide a means for generating
> LRM and RLM. The same, as far as I know, is true for Linux (e.g. gedit).
> 
>  
> 
> Aharon
>