GSettings again

[Geert Janssens]

GnuCash generally has long release cycles. 2.0.0 to 2.2.0 was roughly 3 
years. 2.2.0 to 2.4.0 about 4 years and before 2.6.0 will be release 
another 3 years will have passed.

This got me thinking about GConf/GSettings again. Currently the 
migration is not planned for 2.6. Which means it will make it's 
appearance at best in 2.8. And that would mean we'd have to carry GConf 
around for at least another 3 years.

It is worse actually. To maintain a good user experience we will have to 
make all efforts to migrate all user settings from GConf to GSettings 
the first time they run GnuCash with GSettings support. GConf (as of 
2.31) luckily comes with a tool that can do this migration. Using that 
tool also means we still require GConf to be around as long as we expect 
users to want to migrate. As our policy is that we support migration 
from one major release series to the first next major series (from 2.2.x 
to 2.4.x, from 2.4.x to 2.6.x) that would mean we will need to keep 
GConf around at least one major release cycle next to GSettings. So if 
we only introduce GSettings in 2.8, we will only be able to drop GConf 
in 3.0/2.10. That means at least 6 more years looking at bugs like [1] 
that are inherently tied to GConf's internals.

I'm not looking forward to that. Which inspired me to instead look at 
what would be required to migrate to GSettings  already in 2.6.

Most part is pretty simple:
- Make sure there is a complete schema for all settings keys used. We 
were missing a couple, but I have already added those in my local repo.
- Convert the schema from GConf format to GSettings format. There is a 
tool for that. The end result probably needs a little tweaking, but most 
of the work is done automatically
- Use the GSettings api instead of the GConf one in code. This is pretty 
much straight-forward find and replace stuff.

With that GnuCash is GSettings ready. The trickier part is converting 
the existing preferences from GConf to GSettings. Again there is 
infrastructure to help us.  There is a tool (part of GConf) that can do 
the migration for us. This tool needs a config file as input to know 
which keys from the old system match the keys in the new one.
Again this config file will be fairly easy to write and is well documented.

On linux systems, that's where our job would end. The conversion tool is 
supposed to be run automatically by the desktop environment each time a 
user logs in. I haven't verified if this works, but it does look like 
it. I have updated my linux system several times since GSettings was 
introduced and I never had the feeling I lost any preferences in those 
migrations. Several programs did migrate to GSettings in this time frame.

On to Windows and OS X. On those two platforms we don't have the support 
of the environment to take care of this for us. So we'll have to run the 
conversion tool ourselves at application launch time. The documentation 
states explicitly that it doesn't harm to run the tool more than once 
even. It keeps track by itself whether or not the conversion has 
happened In principle, again not that much work.

On to the caveats:
- To use the migration tool, GConf must be 2.31 or more recent. That in 
itself does raise a few issues.
- The first being this is not available on current Debian stable 
(squeeze). It is on Debian testing. If they continue their trend of the 
last couple of releases the new stable (wheezy) should be around the 
corner while GnuCash 2.6 is only planned for November this year. So I 
don't expect Debian squeeze to backport GnuCash 2.6. But even if they 
do, it should either also backport GConf 2.31 or more recent or worst 
case the user's preferences won't be migrated. This would be 
inconvenient but not dramatical.
- Our Windows build currently ships GConf 2.22, the last version 
available in binary format on the gnome's ftp server. So we'd have to 
build a more recent version ourselves (which I'm currently working on).

Other than these, I don't see any issues that would prevent this from 
being implemented rather sooner than later.

So why do I bring all this up ? Mainly to discuss timing. We more or 
less aimed around this weekend to release our first 2.5 series 
development snapshot. I don't think I can finish the GSettings work this 
weekend. So we have three options:

1. postpone 2.5.0 a little more
2. release 2.5.0 without GSettings and include it in 2.5.1 (which means 
an exception on the feature freeze)
3. don't do GSettings at all in the 2.5/2.6 cycle (not my preference at all)

Can I hear your opinions on this please ?

Thanks,

Geert

[1] https://bugzilla.gnome.org/show_bug.cgi?id=681620