[Feature request] Support for Dynamic Wallpappers supported by other DEs like Gnome/Cinnamon/Mate

[snaggen]

It would be nice to have support for the same dynamic wallpapers as Gnome/Cinamon/Mate since Fedora provides a few out of the box, and there are collections to be found (Just googled and found https://github.com/saint-13/Linux_Dynamic_Wallpapers/ for example). And there are tools available to create them https://github.com/maoschanz/dynamic-wallpaper-editor

I haven't been able to find any official spec, but the xml format seems to be quite straight forward.

An example of the default Fedora 41 Wallpaper

<background>
  <starttime>
    <year>2024</year>
    <month>10</month>
    <day>22</day>
    <hour>8</hour>
    <minute>00</minute>
    <second>00</second>
  </starttime>
<!-- This animation will start at 8 AM. -->

<!-- We start with day at 8 AM. It will remain up for 10 hours. -->
<static>
<duration>36000.0</duration>
<file>/usr/share/backgrounds/f41/default/f41-01-day.png</file>
</static>

<!-- Day ended and starts to transition to night at 6 PM. The transition lasts for 2 hours, ending at 8 PM. -->
<transition type="overlay">
<duration>7200.0</duration>
<from>/usr/share/backgrounds/f41/default/f41-01-day.png</from>
<to>/usr/share/backgrounds/f41/default/f41-01-night.png</to>
</transition>

<!-- It's 8 PM, we're showing the night till 6 AM. -->
<static>
<duration>36000.0</duration>
<file>/usr/share/backgrounds/f41/default/f41-01-night.png</file>
</static>

<!-- It's 6 AM, and we're starting to transition to day. Transition completes at 8 AM. -->
<transition type="overlay">
<duration>7200.0</duration>
<from>/usr/share/backgrounds/f41/default/f41-01-night.png</from>
<to>/usr/share/backgrounds/f41/default/f41-01-day.png</to>
</transition>

</background>

[kbhasi]

I do agree with this, in particular because Debian does a similar thing, as their default backgrounds are created as multiple SVG files for different screen resolutions, then they use a dynamic background XML file to set backgrounds for different screen resolutions in GNOME.

They probably use this same file in other desktop environments too, but I didn't feel like trying to spin up an extra VM to test.

Here's the gnome-background.xml file for the default background in Debian 12, to provide an example.

<background>
  <static>
    <duration>8640000.0</duration>
    <file>
      <size width="1280" height="800">/usr/share/desktop-base/emerald-theme/wallpaper/contents/images/1280x800.svg</size>
      <size width="1280" height="1024">/usr/share/desktop-base/emerald-theme/wallpaper/contents/images/1280x1024.svg</size>
      <size width="1600" height="1200">/usr/share/desktop-base/emerald-theme/wallpaper/contents/images/1600x1200.svg</size>
      <size width="1920" height="1080">/usr/share/desktop-base/emerald-theme/wallpaper/contents/images/1920x1080.svg</size>
      <size width="1920" height="1200">/usr/share/desktop-base/emerald-theme/wallpaper/contents/images/1920x1200.svg</size>
      <size width="2560" height="1440">/usr/share/desktop-base/emerald-theme/wallpaper/contents/images/2560x1440.svg</size>
      <size width="2560" height="1600">/usr/share/desktop-base/emerald-theme/wallpaper/contents/images/2560x1600.svg</size>
      <size width="3200" height="1800">/usr/share/desktop-base/emerald-theme/wallpaper/contents/images/3200x1800.svg</size>
      <size width="3200" height="2000">/usr/share/desktop-base/emerald-theme/wallpaper/contents/images/3200x2000.svg</size>
      <size width="3840" height="2160">/usr/share/desktop-base/emerald-theme/wallpaper/contents/images/3840x2160.svg</size>
      <size width="5120" height="2880">/usr/share/desktop-base/emerald-theme/wallpaper/contents/images/5120x2880.svg</size>
    </file>
  </static>
</background>

The XML file would be stored in the contents folder referenced in the file paths above, with the images folder next to it and containing the actual background files.

COSMIC not yet supporting SVG backgrounds, as far as I can tell, may likely be an upstream issue with image-rs not supporting SVG.

I haven't been able to find any official spec, but the xml format seems to be quite straight forward.

Debian's file name of gnome-background.xml suggests to me that this may be more of a GNOME thing that other desktop environments later implemented.

[mmstick]

COSMIC not yet supporting SVG backgrounds, as far as I can tell, may likely be an upstream issue with image-rs not supporting SVG.

It doesn't matter if image-rs supports it or not. SVG support could be implemented by using resvg.

[kbhasi]

SVG support could be implemented by using resvg.

Right! I had a bit of a half-and-half decision about that and was busy at the time so I didn't check, but thinking about it now, supporting a second library or crate just for SVG files would make more sense. I hadn't yet checked to see how other desktop environments handle this, but I'm certain they too use separate libraries for raster and vector image rendering.

[mmstick]

We're already using different crates for image codecs not supported by image-rs, such as jpeg XL

[kakawait]

At least we may consider kind of new SamplingMethod that is time based.

I'd like to duplicate my Time Shifting SDDM background https://github.com/kakawait/sddm-astronaut-theme

Here 24h speedrun in a few mins (so ignore clock):

That is based on ~200 images (all named 0.png, 1.png, ..., 199.png), thus Alphanumeric sampling is good starting point, but isn't enough because Alphanumeric will always start at 0.png even if not 00:00.

Current workaround is to have a user systemd script at startup that re-order and rename all image to ensure that (pseudo-code) 0.png == ${currentTime}, but is tricks. In addition, UI can't let you edit slideshow time with exact value, only 5mins, 10mins, etc (where in my case I'd like to have 1440 (number of minutes in 1 day) / 200 (number of sampling images) = 7.2 mins). And yes we can change by editing file inside .config/cosmic but each time we open background settings it will override the customization (maybe I could put file to read-only, didn't yet tried).

A time base SamplingMethod with custom sampling window (because isn't always 200 sources files but can be programmatically determined by number of image files inside folder) could be do the stuff without too much rework (except for UI config part)

I could contribute, but atm is more about specs that implementing stuffs, that why I'd like to get feedbacks