Re: [Plib-users] reference counting and simpleStates

[Steve B. <sjb...@ai...>]

"Gouthas, Themie" wrote:
> 
> I noticed when attaching states to tri-strip leaf nodes, that even though
> simpleState derrives from ssgBase, the reference count is unchanged
> and when a scene tree is deleted, the attached ssGsimpleState remains
> allocated.
> 
> Is this a deliberate design feture or a bug?

Coincidentally - I noticed this just last weekend,  I briefly looked at
fixing it - and it's not entirely simple.  I'm also a little concerned
that fixing it will actually break some programs - so we have to tread
carefully and work with our end-users.

The scenario that concerns me is the kind of thing that TuxKart does:

  * Load a set of textures, etc and populate a default set of
    ssgSimpleStates (whose refcounts will now be zero - right?).

  * Load the first racetrack - tell the loader not to create
    materials - but to refer them to the app.  The ref count
    of all those ssgSimpleStates will be incremented,

  * At the end of the race, we delete the scene graph and
    load the next racetrack.  Unfortunately deleting the
    scene graph would decrement the ssgSimpleState's ref
    count to zero...which would make SSG delete them...(which
    it doesn't do right now because of the SSG bug) so
    when the next racetrack is loaded...KABLOOIE!!

So - we *do* need to fix this - but we need to check with
our application authors to ensure that they do an extra 'ref'
to ssgSimpleState's that they need to keep.

This could happen in more subtle ways in packages like FGFS
which pages the scenery from disk on-the-fly.

It's simple enough to fix in the application - but we DO
have to sync up with those guys.

You'll notice that some of the fixes are in the CVS version
right now - but commented out.

-- 
Steve Baker   HomeEmail: <sjb...@ai...>
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