Linux HTML mail agent with RTL and LTR paragraph explicit support

[Eli Zaretskii]

> Date: Mon, 25 Jun 2012 18:21:25 +0300
> From: Dotan Cohen <dotancohen at gmail.com>
> Cc: linux-il at cs.huji.ac.il
> 
> So we have established that sections of text separated by newlines are
> paragraphs. Let us return to the issue. In a plain text file, as
> defined above, there does exist a method by which the author of the
> file may specify that a paragraph is to be RTL. Therefore there is no
> need for HTML to send RTL emails, nor is there technical need for the
> email client to guess. However, I agree that there is practical need
> for the email client to guess as many users may not mark RTL
> paragraphs as RTL (be them plain text or HTML).
> 
> Have I forgotten anything?

Yes, a few things:

 . Base paragraph direction in plain text is determined by the first
   strong directional character in the paragraph.

 . A UBA-compliant MUA will determine the base direction in plain text
   as the UBA specifies, and will display an RTL paragraph starting at
   the right margin of the window.

 . A UBA-compliant MUA _may_ decide that a paragraph is defined by
   something other than a single newline etc. (e.g., Emacs uses the
   high level protocols clause to define a paragraph as text delimited
   by empty lines, i.e. two newlines in a row).  But whatever the
   definition of a paragraph, once a paragraph _is_ detected that
   starts with a string RTL character, a compliant MUA will display it
   as RTL.

 . You can start the paragraph with the RLM or LRM character to force
   its base direction be RTL resp. LTR, because these two have streong
   directionality.