Re: Handling invisible text in bidirectional display

> From: David Kastrup <[email protected]>
> Date: Sat, 16 Jan 2010 20:15:35 +0100
> Cc: [email protected]
> 
> Eli Zaretskii <[email protected]> writes:
> 
> > This is another design decision I needed to make -- how to handle
> > invisible text in the display engine modified to support bidirectional
> > text.
> 
> I think a reasonable model is to display the text as if the invisible
> characters are not there.

I think the resulting change of the visual order will surprise the
users.  It also complicates implementation, which for me is an
important downside.

> Invisibility has other consequences except display, like what cursor
> positions it allows.

For now, I have only implemented strictly logical cursor motion.  That
is, when the next character in the logical (a.k.a. reading) order is
far away on display, C-f causes the cursor jumps to that place, then
subsequent C-f's cause it move to the left.  With this cursor motion,
invisible text in a bidi buffer behaves exactly like it does in Emacs
23.