Re: Persian joining and Pango.

[Aidan Kehoe <kehoea parhasard net>]

 Ar an chéad lá is fiche de mí na Samhain, scríobh Jeff Sparkes: 

 > >  > Editing RTL is wrong, just moving the cursor through the string makes
 > >  > the characters dance.
 > >
 > > Right, I see that too.
 > >
 > 
 > I should have put a smiley there.  RTL is a lot of work, all I know about
 > it is from postings by Eli Zaretskii on emacs-devel list.   I think the
 > dancing characters are caused by having a separate textual_run containing
 > only the character covered by the cursor. I'd just like to get display
 > working well, e.g. for reading email.

The thing is, we already have working RTL on TTYs! Input and display are
grosso modo there already on mlterm and PuTTY. Getting things working on a
GUI should be *easier*, especially with Pango, Uniscribe and the OS X
analogue available.

 > As I understand it, this patch makes the input text be split into chunks,
 > each one containing either all ascii or all non-ascii chars. 

Nope. Under GTK it eliminates splitting input text based on character set
entirely, leaving coverage and font decisions to Pango.

Note that the patch in its current state is architecturally unclean,
otherwise I would have committed it (including non-GTK-specific changes to
the trunk ) back when we had this discussion with Behdad initially.

 > I think even that is unnecessary, but avoiding it would require changing
 > the code flow, right?
 > 
 > I  just checked my current gtk_output_string(), which doesn't call
 > separate_textual_runs at all.   This xlike file patches shouldn't be needed
 > at all.

They are, as far as I can see.

 > WIll the redisplay.c changes break tty display when compiled with gtk?

No. It’s just about possible that Stephen Turnbull, and only Stephen
Turnbull, has configured his TTY XEmacs to use different TTY fonts for
different character sets, but XEmacs is not configured to do that by
default, and I’m sure no-one else has.

-- 
‘Iodine deficiency was endemic in parts of the UK until, through what has been
described as “an unplanned and accidental public health triumph”, iodine was
added to cattle feed to improve milk production in the 1930s.’
(EN Pearce, Lancet, June 2011)