Re: Displaying scrollable images in a grid-layout

[Eli Zaretskii <eliz@gnu.org>]

> From: Andreas Politz <politza@hochschule-trier.de>
> Date: Mon, 13 Apr 2015 10:06:57 +0200
> 
> I'm trying to display a bunch of images in a grid layout, in a
> way that let's me scroll the window over these images, i.e. with
> some displayed only partially at the bottom and/or top.
> 
> Though I couldn't figure out a way of doing it properly, so I'm
> asking here.  The same problems I'm running into can be observed
> with the image-dired.el package.
> 
>     (with-current-buffer (find-file-noselect
> 			  (expand-file-name
> 			   "images"
> 			   data-directory))
>       (dired-unmark-all-marks)
>       (dired-mark-directories nil)
>       (dired-toggle-marks)
>       (image-dired-display-thumbs)
>       (setq-local scroll-conservatively 0)
>       (setq-local scroll-step 0)
>       (setq-local scroll-up-aggressively nil))
> 
> This should create a *image-dired* buffer.  But trying to scroll
> it seems to have no effect:
> 
>     (set-window-vscroll nil (+ (window-vscroll) 1))

I cannot try your recipe, because image-dired-display-thumbs requires
Imagemagick to be installed, which I don't have.  If you can simulate
the same with just a bunch of image files, please show such a recipe,
and I will certainly try looking into it.

That being said, I think you are missing the PIXELWISE-P argument of
both window-vscroll and set-window-vscroll.  Aren't you?  If not,
please elaborate on what kind of partial scrolling did you want to
see.

>     (setq-local scroll-step 1)
>     (set-window-vscroll nil (+ (window-vscroll) 1))
> 
> But it slows down redisplay considerably, to a point where it
> becomes unusable.

And there's one more thing that confuses me in this statement: partial
pixel-wise scrolling will always be slow, so I'm not sure what exactly
you expected to happen.  Probably again it goes back to the fact that
I'm not sure what you were trying to accomplish, or why.