Re: About inline pictures

[David Engster <deng@randomsample.de>]

Ted Zlatanov <tzz@lifelogs.com> writes:
> On Thu, 28 Jan 2010 12:16:49 +0100 David Engster <deng@randomsample.de> wrote: 
>
> DE> You can scroll a buffer through fractional scrolling, but at the same
> DE> the Emacs display engine will make sure that the point always stays
> DE> visible. Therefore, to get a smooth scrolling buffer, you have to make
> DE> sure that the point is always visible while doing the fractional
> DE> scrolling. In image-mode, this is easy since there's only one possible
> DE> point position (namely, point-min).
>
> DE> I've posted my results here:
>
> DE> http://www.randomsample.de/dru5/node/25
>
> DE> I use it to scroll article buffers with images in them. I've also made
> DE> videos showing the normal and fractional scrolling:
>
> DE> http://www.randomsample.de/dru5/node/26
>
> DE> It's not perfect, but it works for me. Of course, this type of scrolling
> DE> is only useful for read-only buffers, since it manipulates the point
> DE> position.
>
> Does fixing this properly require work at the core C level?  Or is your
> approach going to work for everyone?

My approach is more or less a hack. It's really just meant for cases
where you just want to scroll a buffer and don't care about point
position. It's OK for read-only buffers like Gnus articles or emacs-w3m
buffers.

I've thought about making this better, for example by also doing textual
scrolling when possible (i.e. so that images do not suddenly vanish or
pop up). This would set the fractional scrolling back to zero and
hopefully make it possible to use this for editing buffers with images
in them (e.g. AucTeX buffers with enabled preview). But if I remember
correctly, for doing this I would have to know the height of lines which
are currently not displayed, and I think this is not possible in Emacs.

I've also thought about using sliced images in Gnus, but this had other
problems. I'm using a line-spacing >0, so by default, sliced images will
have gaps in them. However, you *can* have different line spacings in a
buffer (see http://www.randomsample.de/dru5/node/24). But in the end, I
didn't try this further, since it became even more hack-ish than the
'fractional scrolling' approach, and I didn't want to mess with the Gnus
and emacs-w3m code for inserting images.

-David