Re: New library wallpaper.el pushed to master

[Stefan Kangas <stefankangas@gmail.com>]

Eli Zaretskii <eliz@gnu.org> writes:

>> BTW, what about actions usually taken to modify the wallpaper such as
>> scaling, cropping, and offsets?  Shouldn't wallpaper-set take several
>> arguments to specify those?
>
> No, I think it should just use the image.  If the user wants to modify
> the image, he/she can do that using "other means", including the
> lately introduced 'image-crop' command.  There's no reason to make
> this simple facility understand too much about images and their
> formats.

I guess what Po Lu had in mind was supporting options such as the
following, from the "feh" man page:

  --bg-center
          Center the file on the background.  If it is too small, it will
          be surrounded by a border as specified by --image-bg.

  --bg-fill
          Like --bg-scale, but preserves aspect ratio by zooming the image
          until it fits.  Either a horizontal or a vertical part of the im‐
          age will be cut off

  --bg-max
          Like --bg-fill, but scale the image to the maximum size that fits
          the screen with borders on one side.  The border color can be set
          using --image-bg.

  --bg-scale
          Fit the file into the background without repeating it, cutting
          off stuff or using borders.  But the aspect ratio is not pre‐
          served either

  --bg-tile
          Tile (repeat) the image in case it is too small for the screen

I think it would be worthwhile to add some defcustoms for this, as this
is likely to be something that users will commonly want to customize.

But I agree with Po Lu that we should try to make this transparent with
regards to the tool.  Perhaps we could add a `wallpaper-default-method'
option with values like `center', `fill', `max', `scale', and `tile'.