Comment 1 for bug 321288

Indeed disper 0.2.0 does not care about primary/secondary display (the panel/deskbars always shown on the primary display). This is now fixed on trunk and will be part of the next release.

By default, the flat-panel display is set as primary display, but this can be overriden by using the -d or --displays command-line option: the first one is the primary display.