Linux HTML mail agent with RTL and LTR paragraph explicit support

[Eli Zaretskii]

> Date: Mon, 25 Jun 2012 21:00:07 +0300
> From: Shachar Shemesh <shachar at shemesh.biz>
> CC: linux-il at cs.huji.ac.il
> 
> On 06/25/2012 08:13 PM, Eli Zaretskii wrote:
> >> Date: Mon, 25 Jun 2012 20:02:48 +0300
> >> From: Shachar Shemesh <shachar at shemesh.biz>
> >> Cc: linux-il at cs.huji.ac.il
> >>
> >>>  Therefore there is no
> >>> need for HTML to send RTL emails, nor is there technical need for the
> >>> email client to guess.
> >> Except there so no standard, de-facto or otherwise (as far as I'm aware)
> >> on whether HL1 is being applied be email clients for plain text emails,
> > Yes, there is such a standard: the UBA.
> HL1 is part of the UBA, even if you, personally, don't like it.

Actually, I do like it.

> Two implementations, opting to use HL1 one and the other not, can
> both conform to the UBA.

True.

> There is no standard on whether HL1 should be applied or not for plain
> text email clients.

True again.

> Outlook employs a higher level protocol. It is "all paragraphs are LTR,
> unless the user presses CTRL+RIGHT SHIFT, in which case all paragraphs
> are RTL". It is a valid, standard conforming protocol

Again, I think such an interpretation is against the spirit of HL1.
Here's the full text:

  HL1. Override P3, and set the paragraph embedding level explicitly. 
  
  . A higher-level protocol may set any paragraph level. This can be
    done on the basis of the context, such as on a table cell,
    paragraph, document, or system level. (P2 may be skipped if P3 is
    overridden). Note that this does not allow a higher-level protocol
    to override the limit specified in BD2.

  . A higher-level protocol may apply rules equivalent to P2 and P3
    but default to level 1 (RTL) rather than 0 (LTR) to match overall
    RTL context.
  
  . A higher-level protocol may use an entirely different algorithm
    that heuristically auto-detects the paragraph embedding level
    based on the paragraph text and its context. For example, it could
    base it on whether there are more RTL characters in the text than
    LTR. As another example, when the paragraph contains no strong
    characters, its direction could be determined by the levels of the
    paragraphs before and after.

This gives examples when a paragraph can be considered RTL even if it
formally doesn't fit the conditions of P3.  I don't understand how
this can be interpreted to mean "all paragraphs are LTR".

But whatever the interpretation, ...

> even if Eli Zaretskii doesn't approve.

... there's no need to get personal.  We can agree to disagree, you
know, and still be able to conduct a civilized discussion, devoid of
ad hominem.

> >   And there can
> > be no high-level protocols that disable determination of base
> > direction of a paragraph altogether.
> HL1 states the exact opposite.

I disagree.

> Last I checked (half an hour ago), it was still part of the
> standard.

True.