Running kde4 applications in the kde3 desktop

Olivier Goffart ogoffart at
Fri Mar 24 18:10:33 GMT 2006

KDE4 application doesn't run fine with kde3 application here.
I don't know if that is happening with anybody, but i have severe problem here

The problem is not in kde4 application itself, but in the kde3 application 
that doesn't run fine anymore once a kde4 application is running
I suspect a problem in kbuildsycoca or in dcopserver.

Try to reproduce:

you are in a normal KDE3 environment

export KDEHOME=~/.kde4  #required or the config will be messed up
export KDEDIRS= ...  ; export PATH= ... ;

run konqueror

at this point, the KDE4's konqueror starts fine.
But now, there are several problems:

Kopete doesn't finds his plugins anymore,  the kopete config dialog is empty.
Same goes for others config dialog like the taskbar one.
KControl can't load anymore some modules

When i try to browse files with konqueror, or any other application (eg the 
open dialog) i get  "Could not talk with KLauncher" message, and it doesn't 

kdesktop (the kde3 one) crashed

for theses reason, the whole kde3 desktop is not usable anymore,  and quitting 
all kde4 applications doesn't help.

I haven't tested to run KDE3 application in a KDE4 environment.

But this is IMO a severe problem that need to be fixed.
KDE4 applications should run nicely in a kde3 environment

If it's a problem with dcopserver, i hope this will be solved when we will 
switch completelly to dbus
If it's a problem with kbuildsycoca which share the same temporaries file, we 
probably should use different temporaries files
(I can only guess a cause, I'm not sure at all what the problem is)

Another problem is the fact that we need to change the KDEHOME variable.
Users probably don't want to do that.

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