Use XDG user configuration settings location

Adding a task for MyApps for ISD to confirm whether both the ~/.<pkgName> and ~/.config/<pkgName> layouts are supported. If so, it will just be a matter of updating the text on the page.

cc'ing Stuart L.

Don't we want to do not just one directory, but .config, .local, and .cache so that it's possible to separate the local machine state from the data? (for things like syncability?)

Some more info.

Nick Barcet says:

Where it says:
"Write all configuration settings to ~/.<pkgName>"

I believe this should be changed at least to "~/.config/<pkgName>" as
freedesktop define "$XDG_CONFIG_HOME defines the base directory relative
to which user specific configuration files should be stored. If
$XDG_CONFIG_HOME is either not set or empty, a default equal to
$HOME/.config should be used." [1]

[1]http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html

Hello! I will update this bug's description because nowadays the website says ~/.config/<package-name>. But the job here isn't done, because we should also be recommending ~/.cache and ~/.local.

This is a pet peeve of mine. I have seen apps that put a lot of data cache files (mp3 files, images, etc) in ~/.config because of this recommendation. This has a direct effect on users. For example, the default backup program deja-dup will automatically ignore ~/.cache but does back up ~/.config by default -- so when apps store large cache data in ~/.config, it wastes users' time and space.

I would request the following text be added to the Technical Requirements section of http://developer.ubuntu.com/publish/my-apps-packages/ :

 * Write all cache files to ~/.cache/<package-name> (This can be one file or a directory containing multiple cache files)
 * Write all user data files to ~/.local/share/<package-name> (This can be one file or a directory containing multiple data files)

And optionally, maybe even link to the XDG spec for full gory details (http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html)

As a developer, I second the motion of allowing applications/games to write cached data to ~/.cache/<package-name>.

David: is this relevant in the new world of Ubuntu apps? Do we need to explain the XDG directories or is this taken care of through the APIs we recommend?

In our new app platform, this is taken care of already:

 - http://developer.ubuntu.com/api/qml/sdk-14.10/Qt.labs.settings.Settings/
 - http://developer.ubuntu.com/api/qml/sdk-14.10/Ubuntu.Components.StateSaver/