Re: Fill column indicator functionality

[Alp Aker]

> I'm sure users will find customizing a character much easier than
> customizing an image.  In any case, I wouldn't give up on allowing a
> character, even if we do support images, because there's no reason to
> restrict users to images.  For example, a suitable selection of a
> character could produce identical displays on GUI and TTY frames,
> something that an image could never do.

I just wanted to expand on this point and clarify my motivations for 
chiming in on this discussion.  I'm very grateful Ergus is doing this 
work, as I've long felt that the functionality of fill-column-indicator 
can only be robustly implemented in the display engine.  I merely want 
to offer my experience as the author of what, until now, has been the 
main package providing this kind of functionality in order to make 
Ergus's work more successful.

When I first implemented fill-column-indicator I used a character-based 
approach and, overwhelmingly, the feedback I received from users 
concerned difficulties in finding and successfully configuring use of a 
font that would provide a seamless visual effect.  When I added the 
option to use XPM images (generated not by the user, but by the package, 
with customization options concerning color, thickness, etc.), users 
only seemed to make use of that.  I've never received a complaint from 
someone wanting to use the package on a system that didn't support XPM 
images.





> > >    . Using the continuous line would cause complications wrt redisplay
> > >      optimizations.  Redisplay of text is highly optimized in Emacs, and
> > >      frequently needs to update only a small portion of the window.  The
> > >      problem is what to do about the indicator line when only some
> > >      portions are redrawn.
> > Unless I'm mistaken, the method I'm describing would allow the same
> > optimizations
> Yes, but I was replying to a completely different idea.  What you
> propose is just a trivial extension of the code posted here, so all of
> the effort that went into that will still be valid, and most of my
> message is not really relevant.