This way it will return a reasonable thing to display as a static unanimated image, which might be the first frame, or something more sophisticated.
And since it's only a little bit more work, add a hidden property to display animations as a wallpaper, the xfconf property is /backdrop/screen#/MonitorName/Workspace#/backdrop-do-animations such as: /backdrop/screen0/monitoreDP1/workspace1/backdrop-do-animations it's a boolean value and setting it to TRUE turns it on, default is obviously off.
c932388 Use gdk's get static image for animation files
src/xfce-backdrop.c | 186 ++++++++++++++++++++++++++++++++++++++++++++------
src/xfce-backdrop.h | 3 +
src/xfce-workspace.c | 14 +++-
3 files changed, 182 insertions(+), 21 deletions(-)