KDE3 apps running in a KDE4-modified environment

[Thiago Macieira]

Andreas Pakulat said:
>> We don't have it yet, but we could have a KDE4HOME variable that
>> overrides
>> KDEHOME for KDE 4 applications. That way, you'll have two separate
>> config
>> directories for your 3 and 4 applications. However, this could hinder
>> the
>> upgrade, because applications will not notice the old config file (maybe
>> we could treat KDEHOME in the presence of KDE4HOME as just one more
>> KDEDIRS...)
>
> But KDEHOME is not about the prefix. In the last days and weeks there
> was some effort to make sure kde4 and kde3 can live in the same prefix.
> But how does this work if application A/kde4 installs a new config file
> in the data dir which A/kde3 doesn't understand? Are there going to be
> different data dirs for kde4 (like share/kde4/apps/<appname> or
> share/apps/kde4/<appname>)?

But KDEHOME is the issue. We're talking about config files and any kind of
file that applications may save to. That only happens in KDEHOME. That's
the only thing that remains of an application after its up or downgrade.

There's no conflict for application-supplied (installed) files. You can't
have the same application for KDE 3 and KDE 4 installed at the same prefix
at the same time. You can have KDE 3 and KDE 4 applications and libraries
in the same prefix, as long as there's no overlap in applications.

Any shared config files in KDEHOME are also shared in KDEDIRS as well.
However, remaining compatible in KDEHOME implies remaining compatible in
KDEDIRS. So we go back to KDEHOME being the issue.

For KDE 3 and 4 to co-exist, anything with the same name must be backwards
compatible, or must be renamed (like we did to kdeinit, kde-config, etc.).

-- 
  Thiago Macieira  -  thiago (AT) macieira.info - thiago (AT) kde.org
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