/usr/share/applications/screensavers/glslideshow.desktop is in xscreensaver-gl 5.15-3+deb7u1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 | [Desktop Entry]
Name=GLSlideshow
Exec=/usr/lib/xscreensaver/glslideshow -root
TryExec=/usr/lib/xscreensaver/glslideshow
Comment=Loads a random sequence of images and smoothly scans and zooms around in each, fading from pan to pan. Written by Jamie Zawinski and Mike Oliphant.
StartupNotify=false
Terminal=false
Type=Application
Categories=Screensaver;
OnlyShowIn=GNOME;
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