[osg-users] context IDs

[Robert Osfield]

Hi Andy,

It's quite a while since I worked specifically on the osg::State,
ContextID, osg::GLExtensions management.  In principle it should be
possible to reuse ContextID's, the sticky issue of whether the
GLExtensions object is recreated for each new graphics context is
something I haven't personally tested.  Looking at osg::State is does
look to clean up the GLExtensions object in 3.4 onwards (I haven't
checked further back)

For graphics performance I would recommend that applications don't go
creating and destroying GraphicsWindows, if possible just hide the
window and reuse it will provide better performance.

Cheers,
Robert.
On Mon, 17 Sep 2018 at 19:08, Andy Skinner <Andy.Skinner at mathworks.com> wrote:
>
> If we get our contextIDs from GraphicsContext::createNewContextID(), it could give us a new number or return a previous one, if we are returning them with GraphicsContext::decrementContextIDUsageCount.  Right?
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> Is there an intended connection between a contextID that has been used and a new one?  It looks to me that extensions are stored per context ID and never reset.
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> So if we change something about what we are looking for in the context (sometimes we fall back to software OpenGL for testing or helping a customer through an issue), we might reuse a context ID, but still have extensions associated with the ID that are not appropriate for it.
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> Am I missing an assumption here?  Should I be able to reuse a contextID for an unrelated context?  If not, I'll just remove call to decrementContextIDUsageCount.  That means the number and various maps will continue to grow.
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> thanks
>
> andy
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