Re: GSettings child schemas

[Geert Janssens <info kobaltwit be>]

Nobody can tell me why or when to use child schemas for accessing keys 
instead of simply using full schema id's ?

How odd...

Geert

Op 01-03-13 13:55, Geert Janssens schreef:
> Hi Osmo,
>
> Thank you for your reply and reference to how you use GSettings. It is 
> a nice example of how you can use child schemas.
>
> What it still does not show me though is *why* I would want to use it.
>
> Let me elaborate a bit on my confusion.
>
> Broadly speaking, to get to the value of a key, you need to know where 
> the key is in the schema. The schema defines both an id and a path. 
> Within a given schema, keys don't have a hierarchy anymore. Hierarchy 
> is created at the schema level.
>
> So each key is uniquely defined by it's schema id and a key name. 
> (ignoring relocatable schemas here for a minute). So if I want my 
> program to get or set a certain key, those two strings are all I need.
>
> You have taken a slightly different approach: you load a base schema 
> and for accessing keys you seem to use the path to each key, starting 
> from the base schema. You have set up child schemas with subpaths for 
> this. But in the end for each key you want to access, you need the 
> full path as well, which is roughly equivalent to knowing the schema 
> id and key name.
>
> So what advantage does it have to set up a hierarchical schema 
> structure using child schemas ?
> Does this have something to do with relocatable schemas and if so, in 
> what way ?
>
> Pointers to a tutorial or more detailed explanation that helps me 
> understand the why of child schemas are welcome.
>
> Geert
>
> Op 01-03-13 12:22, Osmo Antero schreef:
> > Hello,
> > I will not answer to your question directly, but I have implemented
> > GSettings schemas for my audio-recorder app.
> > It may give you some tips. Please take a look at:
> > http://bazaar.launchpad.net/~osmoma/audio-recorder/trunk/view/head:/src/dconf.c 
> >
> > However, do take grated everything is correct and optimally coded ;-)
> >
> > The GNOME-desktop uses normally DConf as Gsettings backend. But that's
> > behind the curtains.
> >
> > Bom fim de semana.
> > Osmo Antero
> >
> >
> > On Fri, Mar 1, 2013 at 10:45 AM, Geert Janssens <info kobaltwit be> 
> > wrote:
> >
> > > Hi,
> > >
> > > I'm working on replacing GConf with GSettings in the GnuCash 
> > > application.
> > > I have read through the GSettings reference documentation and migration
> > > guide. With that I think I can mostly manage the conversion in the 
> > > code.
> > >
> > > I'm unsure about the schema conversion though. I used
> > > gsettings-schema-convert to automatically generate GSettings compatible
> > > schemas from the existing GConf schemas. I notice that for some 
> > > schemas the
> > > conversion tool decided to generate schemas with child schemas.
> > >
> > > For example, after conversion I have these two schemas defined:
> > > <schema id="org.gnucash.general" path="/aps/gnucash/general/">
> > > <schema id="org.gnucash.general.**register" 
> > > path="/apps/gnucash/general/**
> > > register/">
> > >
> > > (Note: I'm aware I should not use the apps for path, but this is only
> > > temporary during the conversion.)
> > >
> > > The second schema is marked as a child schema of the first one.
> > >
> > > Yet due to the way our GConf schemas were organized I also have 
> > > these two
> > > schemas:
> > > <schema id="org.gnucash.dialogs" path="/aps/gnucash/dialogs/">
> > > <schema id="org.gnucash.dialogs.sxs" path="/apps/gnucash/dialogs/**
> > > scheduled_trans/">
> > >
> > > And while they also share the same path and id prefix, the second is 
> > > *not*
> > > marked as a child schema.
> > >
> > > I found the GSettings documentation very thin on the rationale behind
> > > child schemas and hence I have no idea about what would be best 
> > > practise
> > > here.
> > >
> > > Should I attempt to make the schema hierarchy complete, mark schemas as
> > > children of others wherever I can ?
> > > Is it illegal to have two schemas of which one is  in a subpath of the
> > > other without it being a child schema ?
> > > What benefit do I get from defining child schemas ?
> > >
> > > Any advice here would be greatly appreciated.
> > >
> > > Thanks,
> > >
> > > Geert
> > > ______________________________**_________________
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>
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