About inline pictures

About inline pictures

[Harry Putnam]

I wonder if there are already settings that will prevent this problem:

When I open a message that has an image that displays inline, I find
that when I scroll down to bring the picture fully into the message
buffer, unless I'm very careful I inevitably scroll one too many lines
which drops the image instantly before I've actually had a chance to
fully view it.

To reproduce this problem set your emacs Xterminal to something like
a geom. of 96x32, then open the message containing an inline image and
scroll using the enter key to bring the image fully into the frame or
to the last line of the image.   Do it by holding down the `enter'
key.

I find it really hard to see when you've reached the last line of the
image and instead go to far and loose it altogether.  Requiring one to
reopen the message and re-scroll the image. (slowly)

(Of course this assumes the image is has enough size to require
scrolling to see it all)

Seems like there should be a few extra lines of cushion ... maybe
something like 3 lines beyond the last line of image so that its
easier not to scroll too far. 

Re: About inline pictures

[Miles Bader]

Harry Putnam <reader@newsguy.com> writes:
> When I open a message that has an image that displays inline, I find
> that when I scroll down to bring the picture fully into the message
> buffer, unless I'm very careful I inevitably scroll one too many lines
> which drops the image instantly before I've actually had a chance to
> fully view it.
...
> Seems like there should be a few extra lines of cushion ... maybe
> something like 3 lines beyond the last line of image so that its
> easier not to scroll too far. 

Perhaps even better would be for Gnus to do what image-mode does;
I think it basically it slices the image into little strips so vertical
scrolling works much more naturally (image-mode also offers special
bindings to make horizontal scrolling work well, but I dunno how easy it
would be to offer such in Gnus).

Perhaps image-mode already offers a function to do this for embedded
images, or could be refactored to do so...

-Miles

-- 
It wasn't the Exxon Valdez captain's driving that caused the Alaskan oil spill.
It was yours.  [Greenpeace advertisement, New York Times, 25 February 1990]

Re: About inline pictures

[David Engster]

Miles Bader <miles@gnu.org> writes:
> Harry Putnam <reader@newsguy.com> writes:
>> When I open a message that has an image that displays inline, I find
>> that when I scroll down to bring the picture fully into the message
>> buffer, unless I'm very careful I inevitably scroll one too many lines
>> which drops the image instantly before I've actually had a chance to
>> fully view it.
> ...
>> Seems like there should be a few extra lines of cushion ... maybe
>> something like 3 lines beyond the last line of image so that its
>> easier not to scroll too far. 
>
> Perhaps even better would be for Gnus to do what image-mode does;
> I think it basically it slices the image into little strips so vertical
> scrolling works much more naturally (image-mode also offers special
> bindings to make horizontal scrolling work well, but I dunno how easy it
> would be to offer such in Gnus).

Last time I looked, image-mode used fractional scrolling to scroll an
image smoothly. There's also the possibility so slice images, but this
is rarely used, since it has other disadvantages (it depends on
line-spacing being 0, for instance).

> Perhaps image-mode already offers a function to do this for embedded
> images, or could be refactored to do so...

I've fiddled with this stuff some time ago, and it's a harder problem
than I initially thought.

You can scroll a buffer through fractional scrolling, but at the same
the Emacs display engine will make sure that the point always stays
visible. Therefore, to get a smooth scrolling buffer, you have to make
sure that the point is always visible while doing the fractional
scrolling. In image-mode, this is easy since there's only one possible
point position (namely, point-min).

I've posted my results here:

http://www.randomsample.de/dru5/node/25

I use it to scroll article buffers with images in them. I've also made
videos showing the normal and fractional scrolling:

http://www.randomsample.de/dru5/node/26

It's not perfect, but it works for me. Of course, this type of scrolling
is only useful for read-only buffers, since it manipulates the point
position.

-David

Re: About inline pictures

[Ted Zlatanov]

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?

Ted

Re: About inline pictures

[David Engster]

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

Re: About inline pictures

[Lars Magne Ingebrigtsen]

David Engster <deng@randomsample.de> writes:

> I've fiddled with this stuff some time ago, and it's a harder problem
> than I initially thought.

Yeah.  It's really annoying.  You can scroll through an image by tapping
RET, but when you get to the end, the entire picture disappears.

Somebody should fix that.  :-)

-- 
(domestic pets only, the antidote for overdose, milk.)
  larsi@gnus.org * Lars Magne Ingebrigtsen