Comment # 6 on bug 953014 from Wolfgang Bauer

(In reply to Graham Davis from comment #5)
> Just in case anyone's interested, here are the later tests on another
> machine with two versions of 42.1:
> Version of Dolphin on 42.1 beta is 15.04.3-3.5 but built against KDE
> platform 4.14.0.
> Version of Dolphin on 42.1 build 265 is 15.08.2-2.1, built against Qt 5.5.0.

Just to be clear here:
Dolphin 15.04.3 from Beta is the *KDE4* version, dolphin 15.08.2 in RC1 (and
final) is the latest upstrem version that is KF5 based.

> Switching from Beta to 265 loses all tabs and preferences.

Well, I wouldn't expect the KF5 version correctly restore a stored session
state of the KDE4 version. Unfortunate, but not really a bug.
That's why you "lost" the tabs.

It's each application's job to migrate their settings/preferences from KDE4. So
if dolphin doesn't do that, it is a bug in dolphin and should be reported
upstream.

> After setting up new Dolphin windows, including tabs on one, I logged off. I
> did NOT get the warning box! 
> 
> On logging back on, all the windows re-appeared but without the tabs. I
> repeated this test and the same thing happened. 

I just tried this too (13.2, with the latest KF 5.15, Plasma 5.4.2, and Qt5.5.1
packages from the Factory devel repos).
Dolphin did correctly save and restore the tabs and split views including all
shown paths.
This worked reliably when manually saving the session and restoring it at
login.
It also worked with the automatic session management, but then dolphin is not
stored/restored reliably every time. If it was, the tabs were there though.

So I don't see a bug here, except the general problem with Qt5/KF5
applications.

Maybe try to wipe out the folder ~/.config/session/, and remove the file
~/.config/ksmserverrc to start again with a completely clean session.

> This sort of behaviour with Dolphin has happened before in KDE4 and was due to > the formatting within the config files being changed so that one version was
> incompatible with the other. I don't know whether something similar has
> happened here.

I doubt it. Session Management is unrelated to the application's config files.
It's not even possible to configure the number of tabs in the settings I think.

Also, dolphin 15.04 and dolphin 15.08 use completely different config files
anyway, so it cannot really be an incompatibility between the different
versions.

But yes, stored session management sessions from dolphin 15.04 are likely
incompatible with dolphin 15.08.

> Unfortunately, I haven't yet found the location of the new
> config files.

Application's config files are stored in ~/.config/ now, application data in
~/.local/share/.

But I'm not sure about what configuration you are even talking about here.
The view settings are stored in separate .desktop files in each folder, or in
~/.local/share/dolphin/view_settings if you enabled the option "Use common
properties for all folders".

> I'll continue with more tests on this in order to fathom out what the deuce
> is going on. In the event that I find out something more conclusive, I'll do
> as you say and raise it with KDE.

Please do so.
Thanks.