So I don't need a plugin. Great.
I have invoked "foobar2000.exe /?" inside XP's cmd prompt :
Available switches:
/add <list-of-files> - appends the specified files to the current playlist instead of replacing the playlist content and playing them immediately
/immediate - bypasses the "please wait" dialog when adding files
/play, /pause, /playpause, /prev, /next, /rand, /stop - playback controls
/exit - exits foobar2000
/show, /hide - shows or hides the main foobar2000 window
/config - opens the Preferences dialog
/command:<menu command> - invokes the specified main menu command
/playlist_command:<context menu command> - invokes the specified context menu command on current playlist selection
/playing_command:<context menu command> - invokes the specified context menu command on currently played track
/context_command:<context menu command> <files> - invokes the specified context menu command on the specified files
I'm going to try to deal with this... For example, would this command be correct ?
foobar2000.exe /command:View/Dockable Panels/Activate/1 - Peakmeter Spectrum
However, even if it's correct, I think we'll have a problem anyway. Because in the Dockable Panels' "Activate" menu, all panels have a distinctive number (e.g. "1 - Peakmeter Spectrum"). But in the "Collapse" menu, there are no distinctive numbers ! So if we have two Peakmeter Spectrum panels, they will all be named "Peakmeter Spectrum". So how can we differentiate them from the commandline ?