path="" (or not) in GSettings schemas

[Ryan Lortie <desrt desrt ca>]

hi,

One of the big design mistakes I made with GSettings is that this is 
really weird:

  <schema id="org.a11y.atspi" path="/org/a11y/atspi/">

The requirement to specify a separate path is confusing.  It causes 
people to think that maybe the path should have a prefix like /apps/. 
If you manage to avoid this trap and do it properly then it is 
completely redundant.

Of course, it is possible to omit the path to create a relocatable schema.

  <schema id="org.a11y.atspi">

That's the crux of the mistake.

Relocatable schemas are somewhat rare in their use.  The non-relocatable 
case is the 'ordinary one'.  Ideally, the syntax (immediately) above 
should have been reserved to that common case.

Changing this now is a no-go, of course.  There are existing 
applications that use the above syntax to define relocatable schemas.

I propose that we could bail ourselves out of this mess with a two-step 
process, as follows:

1) Start looking for a relocatable='' attribute on <schema>.  If a
   schema has no path and has not been marked as relocatable='yes' then
   emit a warning (similar to what we do for path='/apps/*' already).

2) After a year or so, assume that schemas without relocatable='yes'
   and with no path='' are schemas that wish to have a path
   automatically assigned using the expected '.' to '/' mapping.

In this way we turn:

  <schema id='a.b.c' path='/a/b/c/'>       <!-- common case -->
  <schema id='x.y.z'>                      <!-- uncommon case -->

to:

  <schema id='a.b.c'>                      <!-- common case -->
  <schema id='x.y.z' relocatable='yes'>    <!-- uncommon case -->


Even if we don't do #2, I think doing #1 might be useful.  I don't have 
any evidence (even anecdotal) to support the idea that the current 
situation is confusing but it seems that a helpful warning explaining to 
the user that "<schema id='a.b.c'>" doesn't mean what they think may be 
useful...

Thoughts?