I wanted to add additional molecule definitions to the excellent molecule screensaver. But in the infinite wisdom of Gnome developers, it is not possible to configure your screensaver through a simple GUI. Because that would be too convenient.
Of course, you can always use xscreensaver daemon which allows you to configure your screensavers, but xscreensaver daemon breaks screen locking on activation (i.e. it doesn’t work at all) and that’s a deal-breaker for me.
Luckily, there is a workaround, although it took a while to find it. First, you’ll need to get some PDB files and extract them to a folder accesible to all users on the system. On my system it’s /home/shared/system/molecule, but obviously you can use any folder.
Now we’re going to “create” a screensaver by creating a new .desktop file in /usr/share/applications/screensavers. This folder contains the actual commands which are executed when the screensaver is to be activated. It’s worth mentioning that I’m on Ubuntu 10.10, this folder may have moved in the latest versions.
In any case, copy the existing molecule file and open the copy in the editor:
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$ cd /usr/share/applications/screensavers
$ sudo cp molecule.desktop molecule2.desktop
$ sudo vim molecule2.desktop
Change the Name and Exec line and give molecule the path to your PDB files:
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$ diff molecule.desktop molecule2.desktop
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< Name=Molecule
< Exec=/usr/lib/xscreensaver/molecule -root
---
> Name=Molecule 2
> Exec=/usr/lib/xscreensaver/molecule -root -molecule /home/shared/system/molecule
The screensaver will now appear as “Molecule 2” in the gnome screensaver preferences dialog. You can also check man molecule for more things you can customise.