[osg-submissions] Reuse of context IDs and cleanup of OpenGL resources.

[Mark Sciabica]

Hi Robert,

Running my test program against the 2.3.7 developer release exhibits the 
same errors as 2.2.0. Textures and display lists are not being 
regenerated when a new context reuses a contextID, unless those objects 
are under one of the Context's cameras when the context is destroyed.

Mark

Robert Osfield wrote:
> Hi Mark,
>
> The SVN version of OSG has extra support for deleting and discarding 
> GL object ID's.  I believe this will probably address the problems 
> you've seen.
>
> Could you move to OSG-2.3.7 or OSG-SVN to see if the problem is addressed.
>
> Robert.
>
> On Mon, Apr 14, 2008 at 9:55 PM, Mark Sciabica <msciabica at itracs.com 
> <mailto:msciabica at itracs.com>> wrote:
>
>     These changes are a fix for the bug reported here:
>
>     http://lists.openscenegraph.org/pipermail/osg-users-openscenegraph.org/2008-January/006048.html
>
>      
>
>     Briefly, the bug is that objects that allocate OpenGL resources
>     (e.g. textures or display lists) for a given contextID believe
>     those objects are still valid even after the contextID becomes
>     invalid and then reused by another context.
>
>      
>
>     A source file is attached that reproduces the bug for display
>     lists, textures, and fonts. Other resource types have not been
>     tested, although code has been added to clean up all types that
>     currently clean up their deleted items caches in the
>     GraphicsContext::close function.
>
>      
>
>     The modifications were made against the 2.2.0 branch.
>
>      
>
>     Summary of changes.
>
>      
>
>     1. ContextData now has a list of objects using OpenGL resources
>     for its contextID.
>
>      
>
>     2. Objects using OpenGL resources now add themselves to the above
>     list when they allocate such a resource, and remove themselves
>     when they deallocate it.
>
>      
>
>     3. GraphicsContext::close deallocates the registered resources if
>     no other contexts are using its contextID. Calling
>     releaseGLObjects on the camera now seems redundant so was removed.
>     (Exception: if the _state member of the GraphicsContext is NULL
>     (which it is when close() is called more than once(and it is))
>     then the camera will have its GLObjects released in ALL contexts.
>     This seems incorrect as it needlessly releases objects in
>     unrelated contexts.)
>
>      
>
>     4. ContextData was made an Observer of the objects in its list to
>     avoid dereferencing invalid pointers if those objects are
>     destroyed without deallocating their resources.
>
>      
>
>     5. Static functions that allocate resources and manage a cache of
>     deleted objects were made nonstatic so they could register the
>     object with the context at the time the resource was allocated.
>     They assume the object they're called against is the object owning
>     the resource. These functions have also been made protected to
>     help enforce this.
>
>      
>
>      
>
>     Regards,
>
>      
>
>     Mark
>
>
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