Timelapsed backgrounds

[Soeren Sandmann <sandmann daimi au dk>]

A long time ago I wrote code to do timelapsed backgrounds. I missed
the freeze for 2.20, so now I am submitting it for 2.22.

The idea is that the background gradually fades between a number of
images over the course of a day. One example would be a set of images
taken at the same location at different times of the day.

>From an artist's point of view, the timelapsed background is an XML
file containing filenames of the images to fade between and
indications of how long to show each image.

There is an example background file here:

        http://ssp.fedorapeople.org/background/slides.xml

To see it in action, you'll have to change the filenames to point to
images that exist on your harddisk.


Notes on the patches:

The way this works is by adding a new GnomeBG class to
gnome-desktop. This class has methods to generate thumbnails and
tile/scale/zoom/etc the images. Previously that code was triplicated
in eel, gnome-appearance-capplet, and libbackground. This patch
consolidates all that in the GnomeBG class, so it's actually a net win
in terms of lines of code:

 20 files changed, 2429 insertions(+), 3661 deletions(-)

The GnomeBG class also has a "changed" signal that tells users of the
class that the image needs to be repainted.

I am not sure what best way is to display a time-changing background
in g-a-p. What it currently does is just display a thumbnail that
changes along with the background, but for slowly changing backgrounds
it can be hard to tell that something actually changes.

The patches are here:

        http://ssp.fedorapeople.org/background/

Credits: The idea for this feature came from Diana Fong.



Soren