KDE4 Save Current Session - DBUS to the Rescue

Executive Summary

To cut to the chase, if you want to save your current sessions in KDE4 run the following command from a command line ( or put it in a script that you can call from a desktop shortcut ):

dbus-send --dest=org.kde.ksmserver /KSMServer org.kde.KSMServerInterface.saveCurrentSession

The Details

Now for how I got here in the first place:

I’ve just upgraded to Kubuntu Hardy Heron and decided to give KDE4 a go. I’ll be posting about the upgrade process and KDE4 in general over the coming days but one thing that has kept me “amused” today is the lack of a “Save Current Session” button in KDE4

Rather than have the desktop returned to how it was when I last logged out ( “Restore Previous Session” under KControl ) I like to return to a standard set of applications so I use the “Restore Manually Saved Session” option under KDE 3.5.

In KDE4 KControl there are the same options for the session manager. The snag is that there is no button anywhere to actually save the session when you want to. Thus choosing this option effectively logs you back in to a blank session. This has been reported as a bug in KDE but does not seem to be making any progress.

Flushed with my success with dcop recently I was hoping I could use it with the ksmserver object ( the session manager ) but in KDE4 dcop is not used and the dbus interface is used instead which is a bit more complicated to use.

There is a tool you can install called kdbus that does a similar job to kdcop but I found a much better tool called qdbusviewer along with a useful overview of KDE and dbus here.

To use qdbusviewer you need to install the package qt4-dev-tools then run qdbusviewer from a command line:-

sudo apt-get install qt4-dev-tools

qdbusviewer

You can use qdbusviewer to browser what objects are available and execute methods on them just like kdcop and kdbus ( but kdbus is rather slower )

Internet Hotkeys - Amarok dcop play/pause

Well the solution to getting my Play/Pause button to actually work as a play/pause toggle was pretty easy.

Amarok supports a playPause() method that is registered to the dcop server so in my hotkeys.conf file the command for the Play button became

dcop amarok player playPause

dcop is the command line based client to talk to the dcop server, amarok is of course the application I want to talk to.

player is the section of the amarok services and playPause is the function/method I want to call.

To find this out I used kdcop the graphical interface and explored what it offered under the amarok application.