Re: scrolling images?

[Stefan Monnier]

> The Emacs mail client VM (http://www.wonderworks.com/vm/) divides images
> into strips to allow scrolling. From the documentation of
> vm-mime-use-image-strips:
> 
>     *Non-nil means chop an image into horizontal strip for display. Emacs
>     treats a displayed image as a single large character and cannot scroll
>     vertically within an image. To work around this limitation VM can
>     display an image as a series of contiguous horizontal strips that
>     Emacs' scrolling routines can better handle. To do this VM needs to
>     have the ImageMagick programs 'convert' and 'identify' installed;
>     `vm-imagemagick-convert-program' and `vm-imagemagick-identify-program
>     must point to them.
> 
>     A nil value means VM should display images without cutting them into
>     strips.
> 
> Does that sound like it would be of use?

I think it's a neat workaround, but we want a real solution.
Emacs' display engine is quite capable of scrolling the image by bits,
the only problem is that the elisp scrolling commands work line-by-line.
Also a related problem is that elisp has no easy way to find the pixel-height
of a given line, so it's difficult from elisp to know how much to scroll.


        Stefan